chore: 1.5.1

Every AppImage came out as "cannot tell" because the payload is a
compressed filesystem and none of the Chromium markers is on disk to be
found. The names are reachable, though: squashfs keeps the name of
everything it holds in one table of a few kilobytes, and a name is all
this question needs. That table is now read and inflated in place -
nothing is unpacked, and the image is never run, which a scan started by
the path unit has no business doing anyway.

So a Tauri AppImage such as Modrinth is recognised as WebKitGTK and
dropped from the list instead of being offered as something that could be
switched on - there is no autoscroll in WebKit to ask for - and an
Electron one is covered like any other application.

Left as "cannot tell": lzo and lz4, which squashfs stores as bare blocks
no tool will read without their own framing, and the original ISO9660
layout.

Alongside:

- The detect cache carries a format line. Its entries are keyed on size
  and mtime, so an AppImage that has not changed would otherwise keep
  answering the way an older version decided it did, forever.

- A marker list for whole-tree searches, which is what a Flatpak, a snap
  and an AppImage need. icudtl.dat, snapshot_blob.bin and resources.pak
  are out of it: Flutter ships an icudtl.dat in data/, and next to a
  binary those names are evidence while four directories down they are
  not. The Flatpak and snap searches now share that list.

.gitattributes

@@ -0,0 +1,2 @@
+# Auto detect text files and perform LF normalization
+* text=auto

.github/FUNDING.yml

@@ -0,0 +1,15 @@
+# These are supported funding model platforms
+
+github: Felitendo
+patreon: # Replace with a single Patreon username
+open_collective: # Replace with a single Open Collective username
+ko_fi: felitendo
+tidelift: # Replace with a single Tidelift platform-name/package-name e.g., npm/babel
+community_bridge: # Replace with a single Community Bridge project-name e.g., cloud-foundry
+liberapay: # Replace with a single Liberapay username
+issuehunt: # Replace with a single IssueHunt username
+lfx_crowdfunding: # Replace with a single LFX Crowdfunding project-name e.g., cloud-foundry
+polar: # Replace with a single Polar username
+buy_me_a_coffee: # Replace with a single Buy Me a Coffee username
+thanks_dev: # Replace with a single thanks.dev username
+custom: # Replace with up to 4 custom sponsorship URLs e.g., ['link1', 'link2']

.github/workflows/check.yml

@@ -0,0 +1,28 @@
+name: check
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  check:
+    name: syntax and shellcheck
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+
+      # The Makefile skips whatever is missing rather than failing, so the
+      # tools it looks for have to be here or the check checks less than it
+      # appears to.
+      - name: Install the tools the Makefile looks for
+        run: |
+          sudo apt-get update -qq
+          sudo apt-get install -y --no-install-recommends \
+            shellcheck gettext scdoc
+
+      - run: make check
+
+      - name: Build the catalogs and the man page
+        run: make build

.github/workflows/release.yml

@@ -0,0 +1,256 @@
+name: release
+
+on:
+  push:
+    tags: ['v*']
+  workflow_dispatch:
+    inputs:
+      dry_run:
+        description: >-
+          Build the repositories with a throwaway key and install from them,
+          without publishing anything. This is how the release path gets
+          exercised without cutting a tag.
+        type: boolean
+        default: false
+
+permissions:
+  contents: write
+
+jobs:
+  deb:
+    name: Debian package
+    runs-on: ubuntu-latest
+    container: debian:stable
+    steps:
+      - name: Install the build tools
+        run: |
+          apt-get update -qq
+          apt-get install -y --no-install-recommends \
+            ca-certificates git make gettext scdoc dpkg-dev
+
+      - uses: actions/checkout@v7
+
+      - name: Check the tag against the Makefile
+        run: packaging/check-version.sh "${{ github.ref_name }}"
+
+      - run: packaging/build-deb.sh
+
+      - name: Look inside what was built
+        run: |
+          dpkg-deb --info dist/*.deb
+          dpkg-deb --contents dist/*.deb
+
+      - uses: actions/upload-artifact@v7
+        with:
+          name: deb
+          path: dist/*.deb
+          if-no-files-found: error
+
+  rpm:
+    name: RPM package
+    runs-on: ubuntu-latest
+    container: fedora:latest
+    steps:
+      - name: Install the build tools
+        run: |
+          dnf install -y --setopt=install_weak_deps=False \
+            git make gettext scdoc tar rpm-build rpm-sign systemd-rpm-macros
+
+      - uses: actions/checkout@v7
+
+      - name: Check the tag against the Makefile
+        run: packaging/check-version.sh "${{ github.ref_name }}"
+
+      - run: packaging/build-rpm.sh
+
+      # Signed here rather than alongside the APT repository, because this is
+      # the one place with a native rpm-sign. A dry run signs with a key it
+      # makes on the spot, so the command itself is still exercised.
+      - name: Sign the package
+        env:
+          GPG_PRIVATE_KEY: ${{ secrets.GPG_PRIVATE_KEY }}
+          DRY_RUN: ${{ inputs.dry_run }}
+        run: |
+          if [ "$DRY_RUN" = "true" ]; then
+            gpg --batch --passphrase '' --quick-generate-key \
+              'dry run <dry-run@example.invalid>' rsa2048 sign never
+          elif [ -n "${GPG_PRIVATE_KEY:-}" ]; then
+            printf '%s' "$GPG_PRIVATE_KEY" | gpg --batch --import
+          else
+            echo "No GPG_PRIVATE_KEY secret; leaving the package unsigned."
+            exit 0
+          fi
+          keyid="$(gpg --list-secret-keys --with-colons | awk -F: '/^sec:/ { print $5; exit }')"
+          rpmsign --define "_gpg_name $keyid" --addsign dist/*.rpm
+          gpg --armor --export "$keyid" > dist/rpm-signer.asc
+          rpm --import dist/rpm-signer.asc
+          rpm --checksig dist/*.rpm
+
+      - name: Look inside what was built
+        run: |
+          rpm -qip dist/*.rpm
+          rpm -qlp dist/*.rpm
+
+      - uses: actions/upload-artifact@v7
+        with:
+          name: rpm
+          path: |
+            dist/*.rpm
+            dist/rpm-signer.asc
+          if-no-files-found: error
+
+  publish:
+    name: Release and repositories
+    needs: [deb, rpm]
+    if: startsWith(github.ref, 'refs/tags/v') || inputs.dry_run
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+
+      - uses: actions/download-artifact@v8
+        with:
+          path: incoming
+          merge-multiple: true
+
+      - name: Attach the packages to the release
+        if: ${{ !inputs.dry_run }}
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          gh release create "${{ github.ref_name }}" \
+            --title "${{ github.ref_name }}" \
+            --generate-notes \
+            incoming/*.deb incoming/*.rpm \
+          || gh release upload "${{ github.ref_name }}" \
+            incoming/*.deb incoming/*.rpm --clobber
+
+      - name: Install the repository tools
+        run: |
+          sudo apt-get update -qq
+          sudo apt-get install -y --no-install-recommends \
+            dpkg-dev apt-utils createrepo-c
+
+      - name: Get a signing key
+        id: key
+        env:
+          GPG_PRIVATE_KEY: ${{ secrets.GPG_PRIVATE_KEY }}
+          DRY_RUN: ${{ inputs.dry_run }}
+        run: |
+          if [ "$DRY_RUN" = "true" ]; then
+            gpg --batch --passphrase '' --quick-generate-key \
+              'dry run <dry-run@example.invalid>' rsa2048 sign never
+          elif [ -n "${GPG_PRIVATE_KEY:-}" ]; then
+            printf '%s' "$GPG_PRIVATE_KEY" | gpg --batch --import
+          else
+            echo "present=no" >> "$GITHUB_OUTPUT"
+            echo "::warning::No GPG_PRIVATE_KEY secret - the apt and dnf repositories were not updated. The packages are on the release."
+            exit 0
+          fi
+          echo "present=yes" >> "$GITHUB_OUTPUT"
+
+      - name: Check out the published repositories
+        if: steps.key.outputs.present == 'yes' && !inputs.dry_run
+        uses: actions/checkout@v7
+        with:
+          ref: gh-pages
+          path: pages
+        continue-on-error: true
+
+      - name: Update the repositories
+        if: steps.key.outputs.present == 'yes'
+        run: |
+          # First release, or a dry run: there is no branch to start from.
+          if [ ! -d pages/.git ]; then
+            rm -rf pages && mkdir pages
+            git -C pages init -q -b gh-pages
+            git -C pages remote add origin "https://github.com/${{ github.repository }}.git"
+          fi
+          rm -f incoming/rpm-signer.asc
+          packaging/publish-repos.sh pages incoming
+
+      - name: Check that what was written can be verified
+        if: steps.key.outputs.present == 'yes'
+        run: |
+          find pages -type f -not -path '*/.git/*' | sort
+          echo '--- Release ---'; cat pages/deb/Release
+          echo '--- Packages ---'; cat pages/deb/Packages
+          gpg --verify pages/deb/InRelease
+          gpg --verify pages/deb/Release.gpg pages/deb/Release
+          gpg --verify pages/rpm/repodata/repomd.xml.asc pages/rpm/repodata/repomd.xml
+
+      # The proof that the repository works is apt reading it: the signature,
+      # the index, the dependencies and the program that comes out the far end.
+      - name: Install from the repository that was just built
+        if: inputs.dry_run
+        run: |
+          sudo install -d -m 0755 /etc/apt/keyrings
+          sudo gpg --dearmor -o /etc/apt/keyrings/middleclick-autoscroll.gpg < pages/KEY.gpg
+          echo "deb [signed-by=/etc/apt/keyrings/middleclick-autoscroll.gpg] file://$PWD/pages/deb ./" \
+            | sudo tee /etc/apt/sources.list.d/middleclick-autoscroll.list
+          sudo apt-get update
+          sudo apt-get install -y middleclick-autoscroll
+          middleclick-autoscroll --version
+          middleclick-autoscroll list
+
+      - uses: actions/upload-artifact@v7
+        if: inputs.dry_run
+        with:
+          name: pages
+          path: pages
+          include-hidden-files: true
+
+      - name: Push them
+        if: steps.key.outputs.present == 'yes' && !inputs.dry_run
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          cd pages
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          git add -A
+          git diff --quiet --cached && { echo "nothing changed"; exit 0; }
+          git commit -q -m "Publish ${{ github.ref_name }}"
+          git push "https://x-access-token:${GH_TOKEN}@github.com/${{ github.repository }}.git" HEAD:gh-pages
+
+  verify-dnf:
+    name: Install from the RPM repository
+    needs: publish
+    if: inputs.dry_run
+    runs-on: ubuntu-latest
+    container: fedora:latest
+    steps:
+      - uses: actions/download-artifact@v8
+        with:
+          name: pages
+          path: pages
+
+      # A real run signs the package and the repository metadata with the one
+      # key from the secret. A dry run has no secret, so each job made a key of
+      # its own and both public halves are needed to check both signatures.
+      - uses: actions/download-artifact@v8
+        with:
+          name: rpm
+          path: signer
+
+      - name: Install from the repository that was just built
+        run: |
+          rpm --import pages/KEY.gpg
+          rpm --import signer/rpm-signer.asc
+          cat > /etc/yum.repos.d/middleclick-autoscroll.repo <<EOF
+          [middleclick-autoscroll]
+          name=middleclick-autoscroll
+          baseurl=file://$PWD/pages/rpm
+          enabled=1
+          gpgcheck=1
+          repo_gpgcheck=1
+          gpgkey=file://$PWD/pages/KEY.gpg
+          EOF
+          # util-linux is for runuser below; the base image does not carry it,
+          # and util-linux-core is not the half that has it.
+          dnf install -y middleclick-autoscroll util-linux
+
+          # As somebody, not as root: running it as root is refused, which is
+          # the point of it, and a container is root by default.
+          useradd -m tester
+          runuser -u tester -- middleclick-autoscroll --version
+          runuser -u tester -- middleclick-autoscroll list

.gitignore

@@ -0,0 +1,6 @@
+# build artifacts
+po/*.mo
+doc/*.1
+
+# packages
+dist/

KEY.gpg

@@ -1,29 +0,0 @@
------BEGIN PGP PUBLIC KEY BLOCK-----
-
-mQINBGqMCO8BEAC6rNuAIigcAQpbcTaGd2iJSP2hhaFQbE4YUxwPjxsidrkEOF0c
-cxQq0FTmtBkHRc8DfnPF5/oO0LtL9lokKTVRdzbvm5W2/DM4OwDu3oT/vYlT/yys
-shYEIylOZHj26+Gjrn9xKoQ7A920pu0P0mt5gfU01y4FEz4moydj6SUvApTWvMUI
-9TvPDwKngeulMUst6J+QftjZBZrDqj/L+fH6c+OCGU4sAOBb9nm6/7wp44byFcDV
-TtEdLDlH3CQ8qW9zUN8g1c5/3Au/eHA1cYojNYzZhhhN4g4mGgYPht9CNxaCQkir
-sr4EnTCqWfkgUHC2ZAQ7HTyq/uXyXY7pwlYy50SJXvxN88sZb7lRWqLby1jDvLjW
-fL0Zu1gmq1UXGln+YdhS3iHDrlwfyfGNZXU5NWZubWtbe1v4CUC4Em/chwMmrk9E
-34xF86AQ0PcMuvqomdNNg0eFTfPw/jU0WHLQN49SIzTcH7BFj7bCnY1g9AdmfySH
-8ENPh4ZSLFOykMQChCYK359saOI+B3yqSrE9UI8UaDH638Hu7IRezvlMXBqV5g4K
-9+Zes+5pIzYJuvweUUrFYrxo0RyWpxticGdqZFYeBbDRJf26oqReX8eua2L3ONL1
-MnoeBZF0Vmftg/GA8MqSttCq98eErJb5+hdAgsxAR8gJYIsdniG34ira9wARAQAB
-tDltaWRkbGVjbGljay1hdXRvc2Nyb2xsIHJlcG9zaXRvcnkgPGZlbGl0ZW5kb3l0
-QGdtYWlsLmNvbT6JAk4EEwEKADgWIQRjg8j0Nzst6xSS4qxVo8bfKRRMeQUCaowI
-7wIbAwULCQgHAgYVCgkICwIEFgIDAQIeAQIXgAAKCRBVo8bfKRRMeSBrD/0fL1Mv
-pTIUixusX5sj9yvTuE6hO4XlRD1GymS4McUibFGwmS1FtLZ4REV1B37H4nMDKNJk
-vl2Mr68KEWMbI/MtUKk7vgoIIG/CTcSObl2Az41xQzMXklMV+3/nV2RS4DvPIFmD
-x1Lm/zDhEFTBN0Drasjx3DuvJU4k6ySKiO3JQpVpK6n5ACe3JC1rVaadf/i65e4J
-qeze+Ig5qOq0Dy4ii+3ixDH7sWhVDrTuqzCwcocV+f7TrZYAHGXYkySF6slQGCpQ
-Xre9ZIBTaoRNGpuBaASrVcuVbGl2SddGHfksothMarC3sCKxsDbwf+SUKLi7PjxR
-sE73Kdwv5ErV+JeBkwRv+1UvrxTqrqLZvpBw3aWtg/d0HV9wyPdF8M9/tKRrt3BW
-qYPY+3vmyuTMtFpiM5VSimHBzMTRrNtUo2w/V+BL+BFduZKFIa8jgrwC3QBYTmHV
-VU0/7HYeHkc62CIUcj+mV4UebsydQwerXz4fZgn5UcE2OcuravPu1QiqUV240J/e
-XJMpHgbGXLNrL8QE+x6e4s1irkOccehyuKUydgjTYsTzm1gyfvkM0B4fSFb9BQFF
-aCrQsUYZ7Hwsu1Vj3k2u6uchsXsM6WBsa18ysnGwxUg7Klapuhwfpvcwav3VyvYR
-rhgmwPGHTSHGNmREGwT7uE8Nk8tB0AGOdbbzBg==
-=Yng/
------END PGP PUBLIC KEY BLOCK-----

LICENSE

@@ -0,0 +1,674 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The GNU General Public License is a free, copyleft license for
+software and other kinds of works.
+
+  The licenses for most software and other practical works are designed
+to take away your freedom to share and change the works.  By contrast,
+the GNU General Public License is intended to guarantee your freedom to
+share and change all versions of a program--to make sure it remains free
+software for all its users.  We, the Free Software Foundation, use the
+GNU General Public License for most of our software; it applies also to
+any other work released this way by its authors.  You can apply it to
+your programs, too.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+them if you wish), that you receive source code or can get it if you
+want it, that you can change the software or use pieces of it in new
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+
+  To protect your rights, we need to prevent others from denying you
+these rights or asking you to surrender the rights.  Therefore, you have
+certain responsibilities if you distribute copies of the software, or if
+you modify it: responsibilities to respect the freedom of others.
+
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+
+  Developers that use the GNU GPL protect your rights with two steps:
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+  Some devices are designed to deny users access to install or run
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+<https://www.gnu.org/licenses/why-not-lgpl.html>.

Makefile

@@ -0,0 +1,137 @@
+# middleclick-autoscroll - build and install
+#
+# Everything here is plain shell; "building" only means compiling the gettext
+# catalogs and rendering the man page. Both targets degrade to a no-op when
+# msgfmt/scdoc are missing, so the tree stays usable for development without
+# the build dependencies installed.
+
+# Overridable so a packager can pass the version it is actually building
+# (`make VERSION=$pkgver`). The literal below is the fallback for builds
+# straight from a checkout, and is what a release tag has to carry.
+VERSION      ?= 1.5.1
+
+PREFIX       ?= /usr
+DESTDIR      ?=
+BINDIR       ?= $(PREFIX)/bin
+DATADIR      ?= $(PREFIX)/share
+LIBDIR       ?= $(DATADIR)/middleclick-autoscroll/lib
+LOCALEDIR    ?= $(DATADIR)/locale
+MANDIR       ?= $(DATADIR)/man
+
+# Where systemd looks for user units. For a normal install into /usr this is
+# asked of systemd itself, because the answer is not the same everywhere - a
+# distribution that still keeps /lib separate from /usr/lib says so here - and
+# only guessed at when there is no systemd installed to ask.
+#
+# A build with a prefix of its own keeps the units under that prefix instead,
+# and under share rather than lib. systemd searches both for a system prefix,
+# but only share for a home one: $XDG_DATA_HOME/systemd/user is a search path
+# and ~/.local/lib/systemd/user is not, so an install into ~/.local that put
+# the units in lib would leave the watcher impossible to enable. That prefix is
+# the one an atomic distribution leaves a user - there is no writing to /usr on
+# Bazzite or Silverblue without layering a package and rebooting.
+ifeq ($(PREFIX),/usr)
+USERUNITDIR  ?= $(shell pkg-config --variable=systemduserunitdir systemd 2>/dev/null || echo /usr/lib/systemd/user)
+else
+USERUNITDIR  ?= $(DATADIR)/systemd/user
+endif
+
+LINGUAS      := de
+MOFILES      := $(patsubst %,po/%.mo,$(LINGUAS))
+MANPAGE      := doc/middleclick-autoscroll.1
+
+LIBS         := $(wildcard src/lib/*.sh)
+
+MSGFMT       := $(shell command -v msgfmt 2>/dev/null)
+SCDOC        := $(shell command -v scdoc 2>/dev/null)
+
+.PHONY: all build install uninstall check clean version
+
+all: build
+
+build: $(MOFILES) $(MANPAGE)
+
+# The one place the version is written down, for everything that has to agree
+# with it: the packaging scripts, and the release workflow checking that the
+# tag it was handed says the same thing.
+version:
+	@echo $(VERSION)
+
+po/%.mo: po/%.po
+ifdef MSGFMT
+	$(MSGFMT) --check --output-file=$@ $<
+else
+	@echo "msgfmt not found - skipping $@"
+endif
+
+$(MANPAGE): doc/middleclick-autoscroll.1.scd
+ifdef SCDOC
+	$(SCDOC) < $< > $@
+else
+	@echo "scdoc not found - skipping $@"
+endif
+
+# Syntax-check every shell file, and run shellcheck when it is available.
+check:
+	@set -e; for f in src/middleclick-autoscroll $(LIBS); do \
+		bash -n "$$f" && echo "ok  $$f"; \
+	done
+	@if command -v shellcheck >/dev/null 2>&1; then \
+		shellcheck -x -e SC1090,SC1091 src/middleclick-autoscroll $(LIBS); \
+		echo "ok  shellcheck"; \
+	else \
+		echo "shellcheck not found - skipped"; \
+	fi
+	@if command -v desktop-file-validate >/dev/null 2>&1; then \
+		echo "ok  desktop-file-validate (nothing to check)"; \
+	fi
+
+install: build
+	# executable
+	install -Dm755 src/middleclick-autoscroll \
+		"$(DESTDIR)$(BINDIR)/middleclick-autoscroll"
+
+	# shell libraries
+	install -d "$(DESTDIR)$(LIBDIR)"
+	install -Dm644 -t "$(DESTDIR)$(LIBDIR)" $(LIBS)
+
+	# the version and the resolved paths are baked in at install time
+	sed -i -e 's|@VERSION@|$(VERSION)|g' \
+	       -e 's|@LIBDIR@|$(LIBDIR)|g' \
+	       -e 's|@LOCALEDIR@|$(LOCALEDIR)|g' \
+	       "$(DESTDIR)$(BINDIR)/middleclick-autoscroll" \
+	       "$(DESTDIR)$(LIBDIR)"/*.sh
+
+	# user units: the watcher, and the one-shot it starts
+	install -Dm644 res/systemd/middleclick-autoscroll.service \
+		"$(DESTDIR)$(USERUNITDIR)/middleclick-autoscroll.service"
+	install -Dm644 res/systemd/middleclick-autoscroll.path \
+		"$(DESTDIR)$(USERUNITDIR)/middleclick-autoscroll.path"
+	sed -i -e 's|@BINDIR@|$(BINDIR)|g' \
+		"$(DESTDIR)$(USERUNITDIR)/middleclick-autoscroll.service"
+
+	# translations
+	@for l in $(LINGUAS); do \
+		if [ -f "po/$$l.mo" ]; then \
+			install -Dm644 "po/$$l.mo" \
+				"$(DESTDIR)$(LOCALEDIR)/$$l/LC_MESSAGES/middleclick-autoscroll.mo"; \
+		fi; \
+	done
+
+	# documentation
+	@if [ -f $(MANPAGE) ]; then \
+		install -Dm644 $(MANPAGE) "$(DESTDIR)$(MANDIR)/man1/middleclick-autoscroll.1"; \
+	fi
+	install -Dm644 README.md \
+		"$(DESTDIR)$(DATADIR)/doc/middleclick-autoscroll/README.md"
+
+uninstall:
+	rm -f  "$(DESTDIR)$(BINDIR)/middleclick-autoscroll"
+	rm -rf "$(DESTDIR)$(DATADIR)/middleclick-autoscroll"
+	rm -f  "$(DESTDIR)$(USERUNITDIR)/middleclick-autoscroll.service"
+	rm -f  "$(DESTDIR)$(USERUNITDIR)/middleclick-autoscroll.path"
+	rm -f  "$(DESTDIR)$(MANDIR)/man1/middleclick-autoscroll.1"
+	rm -rf "$(DESTDIR)$(DATADIR)/doc/middleclick-autoscroll"
+
+clean:
+	rm -f po/*.mo $(MANPAGE)

README.md

@@ -0,0 +1,159 @@
+# middleclick-autoscroll
+
+middleclick-autoscroll (what a great name, wow) is a CLI for linux that enables autoscroll in every application that supports it.
+Works with browsers, electron apps like discord and spotify, steam, and anything else that runs on chromium.
+
+This tool looks at which of your apps run chromium under the hood and applies the necessary steps to get autoscrolling working (often just a feature flag). One install, one command and autoscroll _✨just works✨_ (like on windows).
+
+## How to use
+
+Just run `middleclick-autoscroll`. This will open the configuration TUI that looks like this:
+
+```
+  Middle-Click Autoscroll
+
+  Autoscroll                     ON
+
+  Applications covered           11 of 13
+  Not identified                 1 - see the applications list
+  Steam                          ON
+  New applications               ON
+  Middle-click paste             off
+  Last applied                   2 minutes ago
+
+  Applications pick this up the next time they are started.
+
+  [1] Turn autoscroll on or off
+  [2] Re-apply everything
+  [3] Applications
+  [4] Settings
+  [q] Quit
+
+  >
+```
+
+Normally you just need to press `[1]` and the magic is done.
+Pressing `[3]` lets you see every app that was found and toggle each one individually. 
+
+```
+  Applications
+
+  ▸ Steam                              on (Steam)
+    Chromium                           on (launcher)
+    Discord                            on (flag file)
+    Obsidian                           on (launcher)
+    Spotify                            on (launcher)
+    Slack                              off
+    Cursor                             cannot tell
+
+  Up/Down select - Space turns one on or off - q goes back
+```
+
+You can also press `[4]` for more settings.
+
+## How to install
+
+**Arch**
+
+```bash
+yay -S middleclick-autoscroll
+```
+
+**Fedora**
+
+```bash
+sudo curl -fsSL -o /etc/yum.repos.d/middleclick-autoscroll.repo \
+  https://felitendo.github.io/middleclick-autoscroll/middleclick-autoscroll.repo
+sudo dnf install middleclick-autoscroll
+```
+
+**Bazzite**
+
+```bash
+sudo curl -fsSL -o /etc/yum.repos.d/middleclick-autoscroll.repo \
+  https://felitendo.github.io/middleclick-autoscroll/middleclick-autoscroll.repo
+sudo rpm-ostree install middleclick-autoscroll
+systemctl reboot
+```
+
+**Debian**
+
+```bash
+sudo install -d -m 0755 /etc/apt/keyrings
+curl -fsSL https://felitendo.github.io/middleclick-autoscroll/KEY.gpg \
+  | sudo gpg --dearmor -o /etc/apt/keyrings/middleclick-autoscroll.gpg
+echo "deb [signed-by=/etc/apt/keyrings/middleclick-autoscroll.gpg] https://felitendo.github.io/middleclick-autoscroll/deb ./" \
+  | sudo tee /etc/apt/sources.list.d/middleclick-autoscroll.list
+sudo apt update && sudo apt install middleclick-autoscroll
+```
+
+**openSUSE**
+
+```bash
+sudo rpm --import https://felitendo.github.io/middleclick-autoscroll/KEY.gpg
+sudo zypper addrepo --gpgcheck --refresh \
+  https://felitendo.github.io/middleclick-autoscroll/rpm middleclick-autoscroll
+sudo zypper install middleclick-autoscroll
+```
+
+## How it works
+
+Blink (the engine in Chromium, Electron, and CEF) already has autoscroll, but
+it's off on Linux by default because middle click normally pastes the clipboard (??).
+This flag turns it on:
+
+--enable-blink-features=MiddleClickAutoscroll
+
+But doing that for every app is kinda bothersome and it also might break with updates.
+That's why I created this small tool to automate that.
+
+Browsers get the same thing but this time without "blink":
+
+--enable-features=MiddleClickAutoscroll
+
+But both do the same ¯\_(ツ)_/¯
+
+Except in Helium and Brave, which have their own names for it
+(`HeliumMiddleClickAutoscroll`, and Brave's is actually spelled
+`MiddelButtonClickAutoscroll`), so browsers get those as well.
+
+New apps are picked up by a systemd path unit that watches the
+relevant directories. If you hate systemd; `middleclick-autoscroll apply` does the
+same thing manually.
+
+AppImages get looked into as well. The payload is a squashfs image glued onto
+the runtime, and squashfs keeps a small table with the name of every file in
+there - so that table gets read and unpacked (a few kb, nothing is extracted
+and the thing is never run) and the Chromium files are looked for in it. An
+Electron AppImage is covered like any other app; a Tauri one is left alone,
+because WebKitGTK simply has no autoscroll to switch on.
+
+## Commands
+
+| Command | |
+|---|---|
+| `middleclick-autoscroll` | Interactive menu |
+| `… enable` | Turn on, apply, start watching |
+| `… disable` | Undo everything |
+| `… apply` | Apply to new apps |
+| `… apply --rebuild` | Redo from scratch |
+| `… status` | What's covered |
+| `… list` | All apps and how they're handled |
+
+## Building from source
+
+```bash
+make
+sudo make install
+```
+
+Optionally needs `msgfmt` (gettext) for translations and `scdoc` for the man
+page. Supports `PREFIX` and `DESTDIR`. `make check` runs syntax checks and
+shellcheck.
+
+See [packaging/README.md](packaging/README.md) for release builds and repo
+signing.
+
+## License
+
+GPL-3.0-or-later.

deb/InRelease

@@ -1,42 +0,0 @@
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-Codename: stable
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-Date: Thu, 01 Oct 2026 07:37:48 +0000
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------END PGP SIGNATURE-----

deb/Packages

@@ -1,360 +0,0 @@
-Package: middleclick-autoscroll
-Version: 1.1.0
-Architecture: all
-Maintainer: Felitendo <felitendoyt@gmail.com>
-Depends: bash (>= 4.2), coreutils, findutils, grep, sed, mawk | gawk | original-awk
-Recommends: gettext-base, systemd, desktop-file-utils
-Filename: ./middleclick-autoscroll_1.1.0_all.deb
-Size: 35676
-MD5sum: 412f7906e3bc7446d59a0fb9f324d43d
-SHA1: 7a81cb1b9587f319cbe518eddf671f697114b2e1
-SHA256: bb1ac805adf3d161a3b8b3c1a635a9d5b3a8f203c3ca4643e0e944f24308849c
-Section: utils
-Priority: optional
-Homepage: https://github.com/Felitendo/middleclick-autoscroll
-Description: middle-click autoscroll for Chromium-based applications
- Blink - the engine inside Chromium, Electron and CEF - has had Windows-style
- autoscroll for years: hold the middle mouse button, move the pointer, the page
- scrolls. On Linux it is switched off, because middle click is already taken by
- primary-selection paste.
- .
- This turns it back on for every application on the system that can do it, and
- for anything installed later. There is no list of supported applications to
- keep up to date: every launcher is examined, the ones running on Chromium
- underneath are identified by what they ship rather than by their name, and the
- argument goes wherever that particular application will actually read it.
- .
- Nothing outside the user's home directory is ever written to. Run
- "middleclick-autoscroll disable" before removing this package, so that
- everything it changed is put back.
-
-Package: middleclick-autoscroll
-Version: 1.2.0
-Architecture: all
-Maintainer: Felitendo <felitendoyt@gmail.com>
-Depends: bash (>= 4.2), coreutils, findutils, grep, sed, mawk | gawk | original-awk
-Recommends: gettext-base, systemd, desktop-file-utils
-Filename: ./middleclick-autoscroll_1.2.0_all.deb
-Size: 39252
-MD5sum: 65bdc7e1bb274253370edaf3874f04b8
-SHA1: a4067d90327ad3f17ff3ce4ee1ccd15d78e80cf7
-SHA256: 3825984ca49a1faa00a3ee022115a23a48370766ef1db60533fe79eda92ad45f
-Section: utils
-Priority: optional
-Homepage: https://github.com/Felitendo/middleclick-autoscroll
-Description: middle-click autoscroll for Chromium-based applications
- Blink - the engine inside Chromium, Electron and CEF - has had Windows-style
- autoscroll for years: hold the middle mouse button, move the pointer, the page
- scrolls. On Linux it is switched off, because middle click is already taken by
- primary-selection paste.
- .
- This turns it back on for every application on the system that can do it, and
- for anything installed later. There is no list of supported applications to
- keep up to date: every launcher is examined, the ones running on Chromium
- underneath are identified by what they ship rather than by their name, and the
- argument goes wherever that particular application will actually read it.
- .
- Nothing outside the user's home directory is ever written to. Run
- "middleclick-autoscroll disable" before removing this package, so that
- everything it changed is put back.
-
-Package: middleclick-autoscroll
-Version: 1.3.0
-Architecture: all
-Maintainer: Felitendo <felitendoyt@gmail.com>
-Depends: bash (>= 4.2), coreutils, findutils, grep, sed, mawk | gawk | original-awk
-Recommends: gettext-base, systemd, desktop-file-utils
-Filename: ./middleclick-autoscroll_1.3.0_all.deb
-Size: 40756
-MD5sum: 59a98a53aab891b3d09c61949e751eb9
-SHA1: 53638aeff20d5882363a032fecb3a86fd2209fa4
-SHA256: 846e4476e61d20949ad95cdee2d9efb950ac927b18b3926a9a78da3e72a61e04
-Section: utils
-Priority: optional
-Homepage: https://github.com/Felitendo/middleclick-autoscroll
-Description: middle-click autoscroll for Chromium-based applications
- Blink - the engine inside Chromium, Electron and CEF - has had Windows-style
- autoscroll for years: hold the middle mouse button, move the pointer, the page
- scrolls. On Linux it is switched off, because middle click is already taken by
- primary-selection paste.
- .
- This turns it back on for every application on the system that can do it, and
- for anything installed later. There is no list of supported applications to
- keep up to date: every launcher is examined, the ones running on Chromium
- underneath are identified by what they ship rather than by their name, and the
- argument goes wherever that particular application will actually read it.
- .
- Nothing outside the user's home directory is ever written to. Run
- "middleclick-autoscroll disable" before removing this package, so that
- everything it changed is put back.
-
-Package: middleclick-autoscroll
-Version: 1.4.0
-Architecture: all
-Maintainer: Felitendo <felitendoyt@gmail.com>
-Depends: bash (>= 4.2), coreutils, findutils, grep, sed, mawk | gawk | original-awk
-Recommends: gettext-base, systemd, desktop-file-utils
-Filename: ./middleclick-autoscroll_1.4.0_all.deb
-Size: 40256
-MD5sum: e2d66a3b8f3d4e592671e52d0cfd0f24
-SHA1: b489a7e0eb6bbbd15d84ee3592a4e398cb25c732
-SHA256: f7a9f072fd3c8cbde653cd607c1ac43c8e4633b046e2156a679c09bbbaaa42dd
-Section: utils
-Priority: optional
-Homepage: https://github.com/Felitendo/middleclick-autoscroll
-Description: middle-click autoscroll for Chromium-based applications
- Blink - the engine inside Chromium, Electron and CEF - has had Windows-style
- autoscroll for years: hold the middle mouse button, move the pointer, the page
- scrolls. On Linux it is switched off, because middle click is already taken by
- primary-selection paste.
- .
- This turns it back on for every application on the system that can do it, and
- for anything installed later. There is no list of supported applications to
- keep up to date: every launcher is examined, the ones running on Chromium
- underneath are identified by what they ship rather than by their name, and the
- argument goes wherever that particular application will actually read it.
- .
- Nothing outside the user's home directory is ever written to. Run
- "middleclick-autoscroll disable" before removing this package, so that
- everything it changed is put back.
-
-Package: middleclick-autoscroll
-Version: 1.5.0
-Architecture: all
-Maintainer: Felitendo <felitendoyt@gmail.com>
-Depends: bash (>= 4.2), coreutils, findutils, grep, sed, mawk | gawk | original-awk
-Recommends: gettext-base, systemd, desktop-file-utils
-Filename: ./middleclick-autoscroll_1.5.0_all.deb
-Size: 42404
-MD5sum: ae1dca8afb91a648a47a92d33445c470
-SHA1: fb672f06a6b3712cfa7f94c2f35e9f5f36d7562d
-SHA256: 7eeed772e8b5f50fc6f162dfa2d07d5adc03668af44d63027cfe8beadf78e180
-Section: utils
-Priority: optional
-Homepage: https://github.com/Felitendo/middleclick-autoscroll
-Description: middle-click autoscroll for Chromium-based applications
- Blink - the engine inside Chromium, Electron and CEF - has had Windows-style
- autoscroll for years: hold the middle mouse button, move the pointer, the page
- scrolls. On Linux it is switched off, because middle click is already taken by
- primary-selection paste.
- .
- This turns it back on for every application on the system that can do it, and
- for anything installed later. There is no list of supported applications to
- keep up to date: every launcher is examined, the ones running on Chromium
- underneath are identified by what they ship rather than by their name, and the
- argument goes wherever that particular application will actually read it.
- .
- Nothing outside the user's home directory is ever written to. Run
- "middleclick-autoscroll disable" before removing this package, so that
- everything it changed is put back.
-
-Package: middleclick-autoscroll
-Version: 1.5.1
-Architecture: all
-Maintainer: Felitendo <felitendoyt@gmail.com>
-Depends: bash (>= 4.2), coreutils, findutils, grep, sed, mawk | gawk | original-awk
-Recommends: gettext-base, systemd, desktop-file-utils
-Filename: ./middleclick-autoscroll_1.5.1_all.deb
-Size: 46932
-MD5sum: 4cad3fe99518463a266cb0de3bba5e83
-SHA1: d5923ca9e1e911ff9b19ed1c3f1511b2eff8752e
-SHA256: cbe16c7d91bec102d8d1314e2245a895d065c59f281fceb65dceedd16e9c939d
-Section: utils
-Priority: optional
-Homepage: https://github.com/Felitendo/middleclick-autoscroll
-Description: middle-click autoscroll for Chromium-based applications
- Blink - the engine inside Chromium, Electron and CEF - has had Windows-style
- autoscroll for years: hold the middle mouse button, move the pointer, the page
- scrolls. On Linux it is switched off, because middle click is already taken by
- primary-selection paste.
- .
- This turns it back on for every application on the system that can do it, and
- for anything installed later. There is no list of supported applications to
- keep up to date: every launcher is examined, the ones running on Chromium
- underneath are identified by what they ship rather than by their name, and the
- argument goes wherever that particular application will actually read it.
- .
- Nothing outside the user's home directory is ever written to. Run
- "middleclick-autoscroll disable" before removing this package, so that
- everything it changed is put back.
-
-Package: middleclick-autoscroll
-Version: 1.5.2
-Architecture: all
-Maintainer: Felitendo <felitendoyt@gmail.com>
-Depends: bash (>= 4.2), coreutils, findutils, grep, sed, mawk | gawk | original-awk
-Recommends: gettext-base, systemd, desktop-file-utils
-Filename: ./middleclick-autoscroll_1.5.2_all.deb
-Size: 46556
-MD5sum: 41863443b7c4cbc90a73e8423b7470c3
-SHA1: 8283d073de71403a27602b6fa7e67fc4db94cfe9
-SHA256: 9434c9f13980de62df08296dc8042609f7e411bb76a6d391eeb359b3fd3185f1
-Section: utils
-Priority: optional
-Homepage: https://github.com/LoonixTools/middleclick-autoscroll
-Description: middle-click autoscroll for Chromium-based applications
- Blink (the engine inside Chromium, Electron and CEF) has had Windows-style
- autoscroll for years: hold the middle mouse button, move the pointer, the page
- scrolls. On Linux it is switched off, because middle click is already taken by
- primary-selection paste.
- .
- This turns it back on for every application on the system that can do it, and
- for anything installed later. There is no list of supported applications to
- keep up to date: every launcher is examined, the ones running on Chromium
- underneath are identified by what they ship rather than by their name, and the
- argument goes wherever that particular application will actually read it.
- .
- Nothing outside the user's home directory is ever written to. Run
- "middleclick-autoscroll disable" before removing this package, so that
- everything it changed is put back.
-
-Package: middleclick-autoscroll
-Version: 1.5.3
-Architecture: all
-Maintainer: Felitendo <felitendoyt@gmail.com>
-Depends: bash (>= 4.2), coreutils, findutils, grep, sed, mawk | gawk | original-awk
-Recommends: gettext-base, systemd, desktop-file-utils
-Filename: ./middleclick-autoscroll_1.5.3_all.deb
-Size: 46984
-MD5sum: f3276c3151159668d8bc84c002ed0947
-SHA1: 5f022f3357f399037456e94754818d64670acf21
-SHA256: 14564200e11fc2f8592ae24fd5174acf264ebb902acd0294b0624d8de50a0d8a
-Section: utils
-Priority: optional
-Homepage: https://github.com/LoonixTools/middleclick-autoscroll
-Description: middle-click autoscroll for Chromium-based applications
- Blink (the engine inside Chromium, Electron and CEF) has had Windows-style
- autoscroll for years: hold the middle mouse button, move the pointer, the page
- scrolls. On Linux it is switched off, because middle click is already taken by
- primary-selection paste.
- .
- This turns it back on for every application on the system that can do it, and
- for anything installed later. There is no list of supported applications to
- keep up to date: every launcher is examined, the ones running on Chromium
- underneath are identified by what they ship rather than by their name, and the
- argument goes wherever that particular application will actually read it.
- .
- Nothing outside the user's home directory is ever written to. Run
- "middleclick-autoscroll disable" before removing this package, so that
- everything it changed is put back.
-
-Package: middleclick-autoscroll
-Version: 1.5.4
-Architecture: all
-Maintainer: Felitendo <felitendoyt@gmail.com>
-Depends: bash (>= 4.2), coreutils, findutils, grep, sed, mawk | gawk | original-awk
-Recommends: gettext-base, systemd, desktop-file-utils
-Filename: ./middleclick-autoscroll_1.5.4_all.deb
-Size: 47100
-MD5sum: 8a1f13b3e8c2da5e9b9ed8604d828ee9
-SHA1: 1c4a47f8d2f371a25eab00358f04b08dc6286c38
-SHA256: 4309516c39d5788ba7b554a5709bde347c6a9fe5a0dedbba7064946542df7e3d
-Section: utils
-Priority: optional
-Homepage: https://github.com/LoonixTools/middleclick-autoscroll
-Description: middle-click autoscroll for Chromium-based applications
- Blink (the engine inside Chromium, Electron and CEF) has had Windows-style
- autoscroll for years: hold the middle mouse button, move the pointer, the page
- scrolls. On Linux it is switched off, because middle click is already taken by
- primary-selection paste.
- .
- This turns it back on for every application on the system that can do it, and
- for anything installed later. There is no list of supported applications to
- keep up to date: every launcher is examined, the ones running on Chromium
- underneath are identified by what they ship rather than by their name, and the
- argument goes wherever that particular application will actually read it.
- .
- Nothing outside the user's home directory is ever written to. Run
- "middleclick-autoscroll disable" before removing this package, so that
- everything it changed is put back.
-
-Package: middleclick-autoscroll
-Version: 1.6.0
-Architecture: all
-Maintainer: Felitendo <felitendoyt@gmail.com>
-Depends: bash (>= 4.2), coreutils, findutils, grep, sed, mawk | gawk | original-awk
-Recommends: gettext-base, systemd, desktop-file-utils
-Filename: ./middleclick-autoscroll_1.6.0_all.deb
-Size: 60872
-MD5sum: 33fa1bcfc00ac72d6b34d37de5f9b540
-SHA1: 4f13817665c4685c4377ef4f17571d9aad22bb39
-SHA256: 6fdce8ec27270f800559c1d73a13705ec5b22d08c96ca44e1635066a5dcf8815
-Section: utils
-Priority: optional
-Homepage: https://github.com/LoonixTools/middleclick-autoscroll
-Description: middle-click autoscroll for Chromium-based applications
- Blink (the engine inside Chromium, Electron and CEF) has had Windows-style
- autoscroll for years: hold the middle mouse button, move the pointer, the page
- scrolls. On Linux it is switched off, because middle click is already taken by
- primary-selection paste.
- .
- This turns it back on for every application on the system that can do it, and
- for anything installed later. There is no list of supported applications to
- keep up to date: every launcher is examined, the ones running on Chromium
- underneath are identified by what they ship rather than by their name, and the
- argument goes wherever that particular application will actually read it.
- .
- Nothing outside the user's home directory is ever written to. Run
- "middleclick-autoscroll disable" before removing this package, so that
- everything it changed is put back.
-
-Package: middleclick-autoscroll
-Version: 1.6.1
-Architecture: all
-Maintainer: Felitendo <felitendoyt@gmail.com>
-Depends: bash (>= 4.2), coreutils, findutils, grep, sed, mawk | gawk | original-awk
-Recommends: gettext-base, systemd, desktop-file-utils
-Filename: ./middleclick-autoscroll_1.6.1_all.deb
-Size: 62180
-MD5sum: 1e5db5d9d1c300d2c0b512b57764e740
-SHA1: 778d57f5028eda99f849104dc07b5bef681b015d
-SHA256: 881b783d216cb5f15fcf9bf0751bb9af68ba74b4579fea9a02f54acff60bebcc
-Section: utils
-Priority: optional
-Homepage: https://github.com/LoonixTools/middleclick-autoscroll
-Description: middle-click autoscroll for Chromium-based applications
- Blink (the engine inside Chromium, Electron and CEF) has had Windows-style
- autoscroll for years: hold the middle mouse button, move the pointer, the page
- scrolls. On Linux it is switched off, because middle click is already taken by
- primary-selection paste.
- .
- This turns it back on for every application on the system that can do it, and
- for anything installed later. There is no list of supported applications to
- keep up to date: every launcher is examined, the ones running on Chromium
- underneath are identified by what they ship rather than by their name, and the
- argument goes wherever that particular application will actually read it.
- .
- Nothing outside the user's home directory is ever written to. Run
- "middleclick-autoscroll disable" before removing this package, so that
- everything it changed is put back.
-
-Package: middleclick-autoscroll
-Version: 1.7.0
-Architecture: all
-Maintainer: Felitendo <felitendoyt@gmail.com>
-Depends: bash (>= 4.2), coreutils, findutils, grep, sed, mawk | gawk | original-awk
-Recommends: gettext-base, systemd, desktop-file-utils
-Filename: ./middleclick-autoscroll_1.7.0_all.deb
-Size: 65424
-MD5sum: c98e6cce47723c33ced8ebda2883a89e
-SHA1: 876f386d53f142b482c68f8eebc8fa55589d04e3
-SHA256: 9faa1b2e93598594c96eefd3a107f401cd55829e5009c7559492e18f358c8b62
-Section: utils
-Priority: optional
-Homepage: https://github.com/LoonixTools/middleclick-autoscroll
-Description: middle-click autoscroll for Chromium-based applications
- Blink (the engine inside Chromium, Electron and CEF) has had Windows-style
- autoscroll for years: hold the middle mouse button, move the pointer, the page
- scrolls. On Linux it is switched off, because middle click is already taken by
- primary-selection paste.
- .
- This turns it back on for every application on the system that can do it, and
- for anything installed later. There is no list of supported applications to
- keep up to date: every launcher is examined, the ones running on Chromium
- underneath are identified by what they ship rather than by their name, and the
- argument goes wherever that particular application will actually read it.
- .
- Nothing outside the user's home directory is ever written to. Run
- "middleclick-autoscroll disable" before removing this package, so that
- everything it changed is put back.
-

deb/Release

@@ -1,23 +0,0 @@
-Architectures: all
-Codename: stable
-Components: main
-Date: Thu, 01 Oct 2026 07:37:48 +0000
-Label: middleclick-autoscroll
-Origin: middleclick-autoscroll
-Suite: stable
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doc/middleclick-autoscroll.1.scd

@@ -0,0 +1,284 @@
+middleclick-autoscroll(1)
+
+# NAME
+
+middleclick-autoscroll - middle-click autoscroll in every application that supports it
+
+# SYNOPSIS
+
+*middleclick-autoscroll* [_command_]
+
+# DESCRIPTION
+
+Blink, the engine inside Chromium, Electron and CEF, implements Windows-style
+autoscroll: hold the middle mouse button and the page scrolls with the pointer.
+On Linux it is switched off, because middle click is taken by primary-selection
+paste. It can be turned back on with *--enable-blink-features=MiddleClickAutoscroll*
+on the command line.
+
+*middleclick-autoscroll* finds every Chromium-based application on the system
+and puts that argument somewhere the application will actually read it, then
+keeps doing so for anything installed later.
+
+A browser is given *--enable-features=MiddleClickAutoscroll* instead. It asks
+for the same feature - Blink generates a feature of that name for each of its
+runtime flags - but it is not on the list of flags Chromium warns about, so the
+browser does not put a bar reading "You are using an unsupported command-line
+flag" above every page. That spelling only works from Chromium 124 onwards,
+which is why everything else keeps the first one: an application that embeds an
+older Chromium, such as Steam's CEF, has no such bar to show anyway. Two
+browsers know the feature under a name of their own and ignore Chromium's:
+Helium, which is asked for *HeliumMiddleClickAutoscroll* as well, and Brave,
+which is asked for *MiddelButtonClickAutoscroll* - spelled the way Brave spells
+it. A name a browser does not know is ignored. It works on any distribution:
+which of the routes below an application takes is read off its launcher, not
+assumed from where the launcher came from.
+
+Run without a command it shows an interactive menu. Everything it can be told
+is reachable from there; the configuration file behind it does not need to be
+edited by hand.
+
+Nothing outside the user's home directory is written to, and running it as root
+is refused.
+
+# COMMANDS
+
+*enable*
+	Turn autoscroll on, apply it to everything installed, and start watching
+	for new applications.
+
+*disable*
+	Turn it off and put every file that was changed back the way it was.
+
+*apply* [*--rebuild*]
+	Apply to anything that has appeared since the last run. This is what the
+	watcher calls; running it by hand is only needed when the watcher is off.
+
+	Entries left behind by an application that has since been uninstalled are
+	removed here too - the entry shadowing it lives in the user's home, where
+	the package manager that removed the application cannot see it.
+
+	With *--rebuild* everything is taken back first and written again from
+	scratch. That is the repair: it does not care what looks correct already.
+
+*status*
+	How many applications are covered, whether Steam is patched, and when the
+	last run was.
+
+*list*
+	Every Chromium-based application that was found, and how each one is
+	handled.
+
+*-h*, *--help*
+	Show a summary of the commands.
+
+*-V*, *--version*
+	Show the version.
+
+# HOW THE ARGUMENT GETS IN
+
+Two ways, chosen per application.
+
+*Flag file*
+	Where the launcher reads extra arguments from
+	_$XDG_CONFIG_HOME/<name>-flags.conf_. This is the preferred route: it is
+	the supported way to pass arguments, it survives package upgrades, and it
+	applies to a launch from a terminal as much as one from the menu. A
+	feature list that is already in the file is extended rather than
+	duplicated - Chromium keeps only the last occurrence of such an option, so
+	a second one would switch the first one off.
+
+	Arch's Electron and Chromium packages all wrap their binaries this way, and
+	so do a number of individual vendors' launchers elsewhere. Whether a given
+	launcher does is read off the launcher itself, never assumed from the
+	distribution: only one that really names such a file takes this route.
+
+*Desktop entry*
+	For applications that ship their own binary with no wrapper, and for
+	everything inside a Flatpak or a snap, a copy of the desktop entry with the
+	argument appended is written to _~/.local/share/applications_, where it
+	shadows the system one. Entries that already live there - AppImages, web
+	app shortcuts - are edited in place, with the original kept.
+
+	This is the route everything takes on the distributions whose Chromium
+	wrappers keep their equivalent file under _/etc_, where it is the system's
+	to write and not the user's: Debian, Ubuntu, Fedora and openSUSE among
+	them.
+
+	A generated entry is marked *X-MCA-Generated* and an entry edited in place
+	*X-MCA-Patched*. The two are never confused: the first is deleted when
+	undoing, the second is restored from its backup. An entry with neither
+	marker belongs to somebody else and is left alone.
+
+Programs that start themselves at login write their own entry into
+_~/.config/autostart_ pointing straight at their binary, bypassing the menu
+entry entirely. Those are patched in place as well.
+
+Shortcuts on the desktop itself are patched in place too. Nothing in the XDG
+search path looks at that folder, so a shortcut that lives only there would
+otherwise be invisible - and Steam puts one there for every game somebody asks
+for a shortcut to. The folder's name is translated, and the name in use is read
+from _~/.config/user-dirs.dirs_ rather than guessed; the watcher is told about
+it in a drop-in written when autoscroll is turned on.
+
+# STEAM
+
+Steam's interface is CEF and supports the feature, but Steam builds the command
+line for its web helper itself. The only way in is the script that starts the
+helper, inside Steam's own installation:
+
+	~/.local/share/Steam/ubuntu12_64/steamwebhelper_sniper_wrap.sh
+
+Where that installation is depends on how Steam was installed:
+_~/.local/share/Steam_ for Valve's own package and Arch's,
+_~/.steam/debian-installation_ for Debian's, and the private tree of the
+sandbox for the Flatpak and the snap. All of them are looked at.
+
+Steam compares the installed files against its manifest at every start - by
+size and timestamp rather than by content - and restores whatever differs. So
+the patch is written to look untouched: the bytes the argument costs are taken
+back out of the script's own comments and the timestamp is put back afterwards,
+leaving a file exactly as long and exactly as old as Steam left it. A client
+that checks its files finds nothing to repair, and the argument survives
+however Steam was started - from the menu, from a game shortcut, from a
+launcher like Heroic or Lutris, from a terminal.
+
+That is what has to work, because it is the only thing that does. A patch that
+changes the length is never written, whatever else could be done to cover for
+it: Steam checks its files at the shutdown it runs itself as well as at a start
+it was given arguments for, and that one carries no arguments of anybody's. One
+wrong length costs the whole client package downloaded, extracted and installed
+again, and a client that quits at the end of it instead of coming up.
+
+So where the comments cannot pay for the argument, or a client update has
+changed how the helper is started, nothing is written and the status screen
+says Steam is not patched. Nothing goes on Steam's launcher entry, its
+autostart entry or the shortcuts it writes for single games either, and Steam
+goes on repairing its own installation.
+
+An installation patched by an earlier version, which appended where the
+comments were short, is written again to fit at the next apply, or taken back
+if it cannot be made to.
+
+A client update brings a new version of the script. The watcher notices and
+patches it again, and the copy kept for undoing is replaced with the new
+version at the same time, so undoing puts back the script Steam last shipped
+rather than the one from before the update.
+
+# SPOTIFY
+
+The official client is CEF rather than Electron. Installed through
+*spotify-launcher*, it is started by a program that builds its own command line
+and has a configuration file with a slot for extra arguments; that slot is
+where the flag goes. Installed as a plain package, a Flatpak or a snap, it is
+an ordinary desktop entry and needs nothing special.
+
+# MIDDLE-CLICK PASTE
+
+Inside a Chromium application the argument settles this on its own: with
+autoscroll on, Blink stops pasting the primary selection on middle click,
+because the button is doing something else now. Everywhere else on the desktop
+middle click goes on pasting, so the desktop's own switch for it is turned off
+too.
+
+KDE has such a switch, and only for a Wayland session, where the paste is a
+protocol the compositor either offers or does not:
+
+	~/.config/kwinrc, [Wayland], EnablePrimarySelection=false
+
+It is written with *kwriteconfig6*, the same tool System Settings uses, because
+kwinrc has a cascade behind it and entries a distribution can mark immutable;
+an edit that reaches past all that writes something KDE goes on to ignore. KWin
+reads the key once, while it starts, so the change is true from the next login
+on rather than straight away.
+
+What the key said before is recorded, and *disable* puts that back. A key that
+already said *false* before any of this is left alone and not recorded either,
+so a paste the user switched off themselves is never switched back on.
+
+On X11 there is nothing to switch. The primary selection is part of X itself
+and every toolkit reaches for it on its own; no one place can say no. The
+status screen leaves the row out where there is nothing to report.
+
+Turn it off under *Settings* to keep the desktop's middle-click paste.
+
+# APPIMAGES
+
+An AppImage is the AppImage runtime, an ordinary executable, with a squashfs
+image appended to it. The payload is compressed, so none of the files that
+identify Chromium is on disk where it could be found.
+
+The names are, though. squashfs keeps the name of everything it holds in one
+table of its own, a few kilobytes of it, and a name is all this question needs -
+so that table is read and decompressed in place. Nothing is unpacked, and the
+image is never run: this can happen from the watcher, and starting a program
+because it was installed is not something a scan gets to do.
+
+Two kinds of image are still out of reach. One is packed with *lzo* or *lz4*,
+which squashfs stores as bare blocks that neither tool will read without the
+framing their own file formats add. The other is the original AppImage layout,
+which is an ISO9660 filesystem rather than a squashfs one. Both are listed as
+*cannot tell* and left alone until they are switched on from the applications
+screen.
+
+# WHAT HAS NO FLAG AT ALL
+
+Autoscroll is a Blink feature, so only an application drawn by Blink can be
+given it. An application built on WebKitGTK - which is what Tauri uses on
+Linux, and GNOME Web, and anything else linked against libwebkit2gtk - is not
+one of those. WebKit has no equivalent feature to ask for, on any command line
+or in any configuration file.
+
+Such an application is identified as what it is and then left out of the list
+entirely, rather than being offered as something that could be switched on. An
+application that is absent from *list* is absent because there is nothing this
+tool could do for it.
+
+# FILES
+
+_~/.config/middleclick-autoscroll/config_
+	Written by the program. Every option in it is reachable from the menu.
+
+_~/.local/state/middleclick-autoscroll/ledger_
+	One line per change, so *disable* can undo exactly what was done and
+	nothing else.
+
+_~/.local/state/middleclick-autoscroll/backup/_
+	Copies of the files that are edited in place rather than shadowed.
+
+_~/.config/kwinrc_
+	KDE's own configuration. One key in it, *EnablePrimarySelection*, is
+	written when the desktop's middle-click paste is turned off, and put
+	back by *disable*.
+
+_~/.cache/middleclick-autoscroll/detect_
+	Which programs were found to be Chromium, keyed by size and modification
+	time. Its first line says which version of the program wrote it, and a
+	file from an older one is ignored rather than trusted - an entry for a
+	file that has not changed would otherwise never be looked at again.
+	Safe to delete.
+
+# ENVIRONMENT
+
+*NO_COLOR*
+	Disables colour.
+
+# REQUIREMENTS
+
+Bash 4.2 or newer and GNU coreutils. The watcher needs a systemd user session;
+without one everything else works and applications installed later are picked
+up at the next *apply* rather than on their own.
+
+*gzip* is what reads the name table of an AppImage, and *xz* or *zstd* the ones
+packed with those instead. None of the three is required: an image whose
+compressor has no tool installed is listed as *cannot tell*, exactly like the
+two formats there is no reader for at all.
+
+# SEE ALSO
+
+*systemctl*(1), *flatpak*(1), *snap*(8), *kwriteconfig6*(1)
+
+# AUTHORS
+
+Felitendo. Source and issue tracker at
+https://github.com/Felitendo/middleclick-autoscroll

middleclick-autoscroll.repo

@@ -1,7 +0,0 @@
-[middleclick-autoscroll]
-name=middleclick-autoscroll
-baseurl=https://loonixtools.github.io/middleclick-autoscroll/rpm
-enabled=1
-gpgcheck=1
-repo_gpgcheck=1
-gpgkey=https://loonixtools.github.io/middleclick-autoscroll/KEY.gpg

packaging/README.md

@@ -0,0 +1,88 @@
+# Packaging and releases
+
+The Makefile installs everything; these only wrap what it produced. That is
+deliberate — a packaging script that lists the files again is a second
+description of the layout, and two descriptions drift.
+
+| | |
+|---|---|
+| `deb/control`, `deb/copyright` | metadata for the Debian binary package |
+| `rpm/middleclick-autoscroll.spec` | the RPM spec |
+| `build-deb.sh`, `build-rpm.sh` | build one package into `dist/` |
+| `check-version.sh` | refuses a tag that disagrees with the Makefile |
+| `publish-repos.sh` | regenerates the APT and RPM repositories |
+| `pages/` | the landing page and the `.repo` file served from GitHub Pages |
+
+Neither package carries a maintainer script. The units are enabled per user by
+the program itself, and there is nothing to do as root at install time.
+
+## Building one by hand
+
+```bash
+packaging/build-deb.sh      # needs dpkg-dev, gettext, scdoc
+packaging/build-rpm.sh      # needs rpm-build, gettext, scdoc, systemd-rpm-macros
+```
+
+Both take the version from `make version` unless one is passed as the first
+argument.
+
+## Making a release
+
+1. Bump `VERSION` in the Makefile.
+2. Commit, then `git tag vX.Y.Z && git push --tags`.
+
+The `release` workflow builds both packages in a Debian and a Fedora container,
+refuses the tag if it disagrees with the Makefile, attaches the packages to a
+GitHub release, and adds them to the APT and RPM repositories on the `gh-pages`
+branch. Nothing else has to be done by hand.
+
+## Trying the release path first
+
+```bash
+gh workflow run release.yml -f dry_run=true
+```
+
+Builds both packages, builds both repositories with a key generated on the
+spot, checks the three signatures it wrote, and then installs the packages back
+out of the repositories — apt on the runner, dnf in a Fedora container. Nothing
+is pushed and no release is made. This is worth running after any change to the
+packaging, because the alternative is finding out from a tag.
+
+## Setting up the signing, once
+
+The repositories are signed, so this needs a key. Make one that exists for
+nothing else — not a personal key — and give it no passphrase: it lives as an
+encrypted repository secret, and `rpmsign` cannot be handed a passphrase
+unattended.
+
+```bash
+gpg --batch --passphrase '' --quick-generate-key \
+    'middleclick-autoscroll repository <felitendoyt@gmail.com>' rsa4096 sign never
+
+gpg --armor --export-secret-keys 'middleclick-autoscroll repository' \
+    | gh secret set GPG_PRIVATE_KEY
+```
+
+Without the secret the workflow still builds both packages and attaches them to
+the release; it says so in the log and leaves the repositories alone.
+
+## Pointing Pages at it, once — and in this order
+
+The `gh-pages` branch does not exist until a release has put something on it,
+and a branch that does not exist cannot be picked in the Pages settings. So:
+
+1. Set the secret, above.
+2. Tag a release. The workflow creates the branch and fills it.
+3. *Then* set **Pages** to deploy from a branch and pick `gh-pages` at the
+   root.
+
+Doing it the other way round is a wall, and leaving Pages pointed at `main`
+serves the source tree at the address the install instructions name — the key
+and the indexes are 404 and nothing installs.
+
+## What users end up with
+
+The public key is published as `KEY.gpg` beside the repositories, and the
+landing page carries the setup lines for each distribution. After that, a new
+version arrives with `apt upgrade`, `dnf upgrade` or `zypper up` like anything
+else.

packaging/build-deb.sh

@@ -0,0 +1,50 @@
+#!/usr/bin/env bash
+#
+# Builds the binary package for Debian, Ubuntu and their derivatives into
+# dist/.
+#
+# Everything the package contains comes out of `make install`. This only wraps
+# what that produced, so there is exactly one description of where a file goes
+# and it is the Makefile - a packaging script that lists the files again is a
+# second description, and the two drift.
+#
+# Needs: make, dpkg-deb, msgfmt (gettext), scdoc.
+
+set -euo pipefail
+
+here="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")/.." && pwd)"
+version="${1:-$(make -s -C "$here" version)}"
+name=middleclick-autoscroll
+
+# A package without its man page or its translations is not a package this
+# should be quietly willing to produce: the Makefile skips both when the tools
+# are missing, and the result would look like a successful build.
+for tool in msgfmt scdoc dpkg-deb; do
+	command -v "$tool" > /dev/null || { echo "$0: $tool is not installed" >&2; exit 1; }
+done
+
+root="$(mktemp -d)"
+trap 'rm -rf -- "$root"' EXIT
+
+make -C "$here" install \
+	DESTDIR="$root" \
+	PREFIX=/usr \
+	VERSION="$version" \
+	USERUNITDIR=/usr/lib/systemd/user
+
+install -d "$root/DEBIAN"
+sed "s|@VERSION@|$version|g" "$here/packaging/deb/control" > "$root/DEBIAN/control"
+install -Dm644 "$here/packaging/deb/copyright" \
+	"$root/usr/share/doc/$name/copyright"
+
+# Relative to the package root, and DEBIAN/ itself is not part of the contents.
+# Sorted in the C locale so the file comes out the same whatever the locale of
+# the machine that built it.
+( cd "$root" && find . -type f ! -path './DEBIAN/*' -printf '%P\0' \
+	| LC_ALL=C sort -z | xargs -0 md5sum > DEBIAN/md5sums )
+
+mkdir -p "$here/dist"
+out="$here/dist/${name}_${version}_all.deb"
+dpkg-deb --root-owner-group --build "$root" "$out" > /dev/null
+
+echo "$out"

packaging/build-rpm.sh

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+#
+# Builds the binary package for Fedora, RHEL, openSUSE and their derivatives
+# into dist/.
+#
+# The spec takes the version as a macro rather than carrying one of its own,
+# for the same reason the Debian control file has a placeholder: the Makefile
+# is where the version is written down.
+#
+# Needs: rpmbuild, make, msgfmt (gettext), scdoc, systemd-rpm-macros.
+
+set -euo pipefail
+
+here="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")/.." && pwd)"
+version="${1:-$(make -s -C "$here" version)}"
+name=middleclick-autoscroll
+
+command -v rpmbuild > /dev/null || { echo "$0: rpmbuild is not installed" >&2; exit 1; }
+
+top="$(mktemp -d)"
+trap 'rm -rf -- "$top"' EXIT
+mkdir -p "$top"/{BUILD,BUILDROOT,RPMS,SOURCES,SPECS}
+
+# The working tree as it is, not as it was committed: a package built from a
+# checkout has to contain what is in that checkout.
+tar czf "$top/SOURCES/$name-$version.tar.gz" \
+	--transform "s,^\\.,$name-$version," \
+	--exclude=./.git --exclude=./dist --exclude=./po/'*.mo' \
+	-C "$here" .
+
+rpmbuild \
+	--define "_topdir $top" \
+	--define "_version $version" \
+	-bb "$here/packaging/rpm/$name.spec" > /dev/null
+
+mkdir -p "$here/dist"
+cp "$top"/RPMS/noarch/*.rpm "$here/dist/"
+
+ls "$here/dist/$name-$version"*.rpm

packaging/check-version.sh

@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+#
+# Refuses a release whose tag and Makefile disagree.
+#
+# The version is baked into the program at install time from the Makefile, and
+# the packages take theirs from the same place - but the tag is what people see
+# and what the release is named after. A tag that says something else produces
+# a package called 1.0.4 containing a program that reports 1.0.3, and nothing
+# would have complained.
+#
+# Anything that is not a v-tag - a run started by hand from a branch - is not a
+# release and has nothing to check.
+
+set -euo pipefail
+
+here="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")/.." && pwd)"
+ref="${1:-}"
+
+case "$ref" in
+	v[0-9]*) ;;
+	*)
+		echo "not a release tag (${ref:-none}) - nothing to check against"
+		exit 0
+		;;
+esac
+
+tag_version="${ref#v}"
+make_version="$(make -s -C "$here" version)"
+
+if [[ $tag_version != "$make_version" ]]; then
+	echo "tag $ref says $tag_version, the Makefile says $make_version" >&2
+	echo "Bump VERSION in the Makefile to match the tag, or retag." >&2
+	exit 1
+fi
+
+echo "$ref matches the Makefile"

packaging/deb/control

@@ -0,0 +1,24 @@
+Package: middleclick-autoscroll
+Version: @VERSION@
+Section: utils
+Priority: optional
+Architecture: all
+Maintainer: Felitendo <felitendoyt@gmail.com>
+Depends: bash (>= 4.2), coreutils, findutils, grep, sed, mawk | gawk | original-awk
+Recommends: gettext-base, systemd, desktop-file-utils
+Homepage: https://github.com/Felitendo/middleclick-autoscroll
+Description: middle-click autoscroll for Chromium-based applications
+ Blink - the engine inside Chromium, Electron and CEF - has had Windows-style
+ autoscroll for years: hold the middle mouse button, move the pointer, the page
+ scrolls. On Linux it is switched off, because middle click is already taken by
+ primary-selection paste.
+ .
+ This turns it back on for every application on the system that can do it, and
+ for anything installed later. There is no list of supported applications to
+ keep up to date: every launcher is examined, the ones running on Chromium
+ underneath are identified by what they ship rather than by their name, and the
+ argument goes wherever that particular application will actually read it.
+ .
+ Nothing outside the user's home directory is ever written to. Run
+ "middleclick-autoscroll disable" before removing this package, so that
+ everything it changed is put back.

packaging/deb/copyright

@@ -0,0 +1,20 @@
+Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
+Upstream-Name: middleclick-autoscroll
+Source: https://github.com/Felitendo/middleclick-autoscroll
+
+Files: *
+Copyright: 2026 Felitendo
+License: GPL-3+
+
+License: GPL-3+
+ This program is free software: you can redistribute it and/or modify it under
+ the terms of the GNU General Public License as published by the Free Software
+ Foundation, either version 3 of the License, or (at your option) any later
+ version.
+ .
+ This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ .
+ On Debian systems the full text of the GNU General Public License version 3 can
+ be found in /usr/share/common-licenses/GPL-3.

packaging/pages/index.html

@@ -64,35 +64,35 @@
 
 <h1>middleclick-autoscroll</h1>
 <p class="lead">
-  Middle-click autoscroll in every Chromium-based application on the system,
+  Middle-click autoscroll — hold the middle mouse button, move the pointer, the
-  and in anything installed later: hold the middle mouse button, move the
+  page scrolls — in every Chromium-based application on the system, and in
-  pointer, and the page scrolls.
+  anything installed later.
 </p>
 
 <p>
   This page is the package repository. Set it up once and every new version
   arrives with the rest of your system updates. The
-  <a href="https://github.com/LoonixTools/middleclick-autoscroll">source and the
+  <a href="https://github.com/Felitendo/middleclick-autoscroll">source and the
   documentation</a> are on GitHub.
 </p>
 
 <h2>Debian, Ubuntu, Linux Mint, Pop!_OS</h2>
 <pre><code>sudo install -d -m 0755 /etc/apt/keyrings
-curl -fsSL https://loonixtools.github.io/middleclick-autoscroll/KEY.gpg \
+curl -fsSL @BASEURL@/KEY.gpg \
   | sudo gpg --dearmor -o /etc/apt/keyrings/middleclick-autoscroll.gpg
-echo "deb [signed-by=/etc/apt/keyrings/middleclick-autoscroll.gpg] https://loonixtools.github.io/middleclick-autoscroll/deb ./" \
+echo "deb [signed-by=/etc/apt/keyrings/middleclick-autoscroll.gpg] @BASEURL@/deb ./" \
   | sudo tee /etc/apt/sources.list.d/middleclick-autoscroll.list
 sudo apt update
 sudo apt install middleclick-autoscroll</code></pre>
 
 <h2>Fedora, RHEL, CentOS Stream</h2>
 <pre><code>sudo curl -fsSL -o /etc/yum.repos.d/middleclick-autoscroll.repo \
-  https://loonixtools.github.io/middleclick-autoscroll/middleclick-autoscroll.repo
+  @BASEURL@/middleclick-autoscroll.repo
 sudo dnf install middleclick-autoscroll</code></pre>
 
 <h2>openSUSE</h2>
-<pre><code>sudo rpm --import https://loonixtools.github.io/middleclick-autoscroll/KEY.gpg
+<pre><code>sudo rpm --import @BASEURL@/KEY.gpg
-sudo zypper addrepo --gpgcheck --refresh https://loonixtools.github.io/middleclick-autoscroll/rpm middleclick-autoscroll
+sudo zypper addrepo --gpgcheck --refresh @BASEURL@/rpm middleclick-autoscroll
 sudo zypper install middleclick-autoscroll</code></pre>
 
 <h2>Arch, CachyOS, EndeavourOS, Manjaro</h2>
@@ -103,12 +103,12 @@ sudo zypper install middleclick-autoscroll</code></pre>
 <p>
   That is the whole setup. Nothing else has to be configured and no file has to
   be edited. Run <code>middleclick-autoscroll disable</code> before removing the
-  package. It puts back everything that was changed.
+  package — it puts back everything that was changed.
 </p>
 
 <footer>
   GPL-3.0-or-later. Packages are signed; the public key is
-  <a href="https://loonixtools.github.io/middleclick-autoscroll/KEY.gpg">KEY.gpg</a>.
+  <a href="@BASEURL@/KEY.gpg">KEY.gpg</a>.
 </footer>
 
 </body>

packaging/pages/middleclick-autoscroll.repo

@@ -0,0 +1,7 @@
+[middleclick-autoscroll]
+name=middleclick-autoscroll
+baseurl=@BASEURL@/rpm
+enabled=1
+gpgcheck=1
+repo_gpgcheck=1
+gpgkey=@BASEURL@/KEY.gpg

packaging/publish-repos.sh

@@ -0,0 +1,88 @@
+#!/usr/bin/env bash
+#
+# Puts the packages that were just built into the APT and RPM repositories on
+# the gh-pages branch, and regenerates the indexes over everything that is
+# there.
+#
+# Old versions are kept rather than replaced. An index built over all of them
+# is what lets somebody pin a version or go back to one, and it costs a few
+# hundred kilobytes.
+#
+# Usage: publish-repos.sh <gh-pages checkout> <directory of new packages>
+#
+# Needs: dpkg-dev, apt-utils, createrepo-c, gpg, and a secret key already
+# imported - its id is taken from the keyring.
+
+set -euo pipefail
+
+pages="$(cd -- "$1" && pwd)"
+incoming="$(cd -- "$2" && pwd)"
+here="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")/.." && pwd)"
+
+base_url="${MCA_REPO_URL:-https://felitendo.github.io/middleclick-autoscroll}"
+
+keyid="$(gpg --list-secret-keys --with-colons | awk -F: '/^sec:/ { print $5; exit }')"
+[[ -n $keyid ]] || { echo "$0: no secret key in the keyring" >&2; exit 1; }
+
+mkdir -p "$pages/deb" "$pages/rpm"
+cp -- "$incoming"/*.deb "$pages/deb/"
+cp -- "$incoming"/*.rpm "$pages/rpm/"
+
+# ---------------------------------------------------------------------------
+# APT
+# ---------------------------------------------------------------------------
+# A flat repository: the packages and their index sit in one directory and the
+# sources line ends in "./". There is one distribution here and it is the same
+# package for all of them, so the suite and component machinery of a pool
+# layout would describe nothing.
+(
+	cd "$pages/deb"
+
+	# The old index must be gone before the new one is written: apt-ftparchive
+	# hashes every file in the directory, and a Release that hashes the
+	# previous Release is a Release that cannot be verified.
+	rm -f Packages Packages.gz Release Release.gpg InRelease
+
+	dpkg-scanpackages --multiversion . > Packages
+	gzip -9kf Packages
+
+	apt-ftparchive \
+		-o APT::FTPArchive::Release::Origin=middleclick-autoscroll \
+		-o APT::FTPArchive::Release::Label=middleclick-autoscroll \
+		-o APT::FTPArchive::Release::Suite=stable \
+		-o APT::FTPArchive::Release::Codename=stable \
+		-o APT::FTPArchive::Release::Architectures=all \
+		-o APT::FTPArchive::Release::Components=main \
+		release . > Release
+
+	# Both signatures: InRelease is what current apt fetches, Release.gpg is
+	# what an older one falls back to.
+	gpg --batch --yes --local-user "$keyid" --clearsign --output InRelease Release
+	gpg --batch --yes --local-user "$keyid" --detach-sign --armor --output Release.gpg Release
+)
+
+# ---------------------------------------------------------------------------
+# RPM
+# ---------------------------------------------------------------------------
+(
+	cd "$pages/rpm"
+	createrepo_c --quiet --update .
+	rm -f repodata/repomd.xml.asc
+	gpg --batch --yes --local-user "$keyid" --detach-sign --armor repodata/repomd.xml
+)
+
+# ---------------------------------------------------------------------------
+# The key and the landing page
+# ---------------------------------------------------------------------------
+gpg --armor --export "$keyid" > "$pages/KEY.gpg"
+
+sed "s|@BASEURL@|$base_url|g" "$here/packaging/pages/index.html" > "$pages/index.html"
+sed "s|@BASEURL@|$base_url|g" "$here/packaging/pages/middleclick-autoscroll.repo" \
+	> "$pages/middleclick-autoscroll.repo"
+
+# Pages would otherwise hand the whole directory to Jekyll, which drops every
+# file whose name starts with an underscore and can rewrite the rest.
+touch "$pages/.nojekyll"
+
+echo "signed with $keyid"
+ls -1 "$pages/deb" "$pages/rpm"

packaging/rpm/middleclick-autoscroll.spec

@@ -0,0 +1,72 @@
+# Built with `packaging/build-rpm.sh`, which passes the version in rather than
+# editing this file: the Makefile is where the version is written down, and two
+# places that have to agree are one place too many.
+%global upstream_version %{?_version}%{!?_version:1.0.3}
+
+Name:           middleclick-autoscroll
+Version:        %{upstream_version}
+Release:        1%{?dist}
+Summary:        Middle-click autoscroll for Chromium-based applications
+
+License:        GPL-3.0-or-later
+URL:            https://github.com/Felitendo/middleclick-autoscroll
+Source0:        %{name}-%{version}.tar.gz
+
+BuildArch:      noarch
+BuildRequires:  make
+BuildRequires:  gettext
+BuildRequires:  scdoc
+# For %{_userunitdir}, which is where the watcher's user units belong.
+BuildRequires:  systemd-rpm-macros
+
+Requires:       bash >= 4.2
+Requires:       coreutils
+Requires:       findutils
+Requires:       grep
+Requires:       sed
+Requires:       gawk
+
+# The interface falls back to English without gettext and picks up new
+# applications at the next `apply` without systemd, so neither is required.
+Recommends:     /usr/bin/gettext
+Recommends:     systemd
+Recommends:     desktop-file-utils
+
+%description
+Blink - the engine inside Chromium, Electron and CEF - has had Windows-style
+autoscroll for years: hold the middle mouse button, move the pointer, the page
+scrolls. On Linux it is switched off, because middle click is already taken by
+primary-selection paste.
+
+This turns it back on for every application on the system that can do it, and
+for anything installed later. There is no list of supported applications to keep
+up to date: every launcher is examined, the ones running on Chromium underneath
+are identified by what they ship rather than by their name, and the argument goes
+wherever that particular application will actually read it.
+
+Nothing outside the user's home directory is ever written to. Run
+"middleclick-autoscroll disable" before removing this package, so that everything
+it changed is put back.
+
+%prep
+%autosetup -n %{name}-%{version}
+
+%build
+%make_build VERSION=%{upstream_version}
+
+%install
+%make_install PREFIX=%{_prefix} VERSION=%{upstream_version} \
+	USERUNITDIR=%{_userunitdir}
+
+%find_lang %{name}
+
+%files -f %{name}.lang
+%license LICENSE
+%doc %{_datadir}/doc/%{name}/README.md
+%{_bindir}/%{name}
+%{_datadir}/%{name}/
+%{_userunitdir}/%{name}.path
+%{_userunitdir}/%{name}.service
+%{_mandir}/man1/%{name}.1*
+
+%changelog

po/de.po

@@ -0,0 +1,244 @@
+# Translation template for middleclick-autoscroll.
+# Copyright (C) 2026 Felitendo
+# This file is distributed under the same license as middleclick-autoscroll.
+#
+msgid ""
+msgstr ""
+"Project-Id-Version: middleclick-autoscroll 1.0.3\n"
+"Report-Msgid-Bugs-To: https://github.com/Felitendo/middleclick-autoscroll/issues\n"
+"POT-Creation-Date: 2026-08-16 00:00+0200\n"
+"PO-Revision-Date: 2026-08-16 00:00+0200\n"
+"Last-Translator: Felitendo\n"
+"Language-Team: German\n"
+"Language: de\n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=UTF-8\n"
+"Content-Transfer-Encoding: 8bit\n"
+
+#. Status labels
+msgid "ON"
+msgstr "AN"
+
+msgid "OFF"
+msgstr "AUS"
+
+msgid "on"
+msgstr "an"
+
+msgid "off"
+msgstr "aus"
+
+msgid "(none)"
+msgstr "(keine)"
+
+msgid "flag file"
+msgstr "Flag-Datei"
+
+msgid "launcher"
+msgstr "Startereintrag"
+
+msgid "cannot tell"
+msgstr "nicht erkennbar"
+
+msgid "not patched yet"
+msgstr "noch nicht gepatcht"
+
+
+#. Status block
+msgid "Autoscroll"
+msgstr "Autoscroll"
+
+msgid "Applications covered"
+msgstr "Abgedeckte Anwendungen"
+
+msgid "%d of %d"
+msgstr "%d von %d"
+
+msgid "Not identified"
+msgstr "Nicht erkannt"
+
+msgid "%d - see the applications list"
+msgstr "%d – siehe Anwendungsliste"
+
+msgid "Steam"
+msgstr "Steam"
+
+msgid "Middle-click paste"
+msgstr "Mittelklick-Einfügen"
+
+msgid "New applications"
+msgstr "Neue Anwendungen"
+
+msgid "Last applied"
+msgstr "Zuletzt angewendet"
+
+msgid "Applications pick this up the next time they are started."
+msgstr "Anwendungen übernehmen das beim nächsten Start."
+
+
+#. Menu
+msgid "Turn autoscroll on or off"
+msgstr "Autoscroll ein- oder ausschalten"
+
+msgid "Re-apply everything"
+msgstr "Alles neu anwenden"
+
+msgid "Applications"
+msgstr "Anwendungen"
+
+msgid "Settings"
+msgstr "Einstellungen"
+
+msgid "Quit"
+msgstr "Beenden"
+
+msgid "Press any key to continue..."
+msgstr "Beliebige Taste drücken …"
+
+
+#. Settings
+msgid "Electron and CEF applications"
+msgstr "Electron- und CEF-Anwendungen"
+
+msgid "Chromium-based browsers"
+msgstr "Chromium-basierte Browser"
+
+msgid "Flatpak applications"
+msgstr "Flatpak-Anwendungen"
+
+msgid "Snap applications"
+msgstr "Snap-Anwendungen"
+
+msgid "Programs that start themselves at login"
+msgstr "Programme, die sich beim Anmelden selbst starten"
+
+msgid "Spotify"
+msgstr "Spotify"
+
+msgid "Turn off KDE's middle-click paste"
+msgstr "KDEs Mittelklick-Einfügen abschalten"
+
+msgid "Apply to newly installed applications"
+msgstr "Auf neu installierte Anwendungen anwenden"
+
+msgid "Additional Chromium arguments"
+msgstr "Zusätzliche Chromium-Argumente"
+
+msgid "Up/Down select - Space or Right changes - q goes back"
+msgstr "Hoch/Runter wählt – Leertaste oder Rechts ändert – q geht zurück"
+
+msgid "Arguments separated by spaces, empty for none:"
+msgstr "Argumente mit Leerzeichen getrennt, leer für keine:"
+
+msgid "Could not save the setting."
+msgstr "Einstellung konnte nicht gespeichert werden."
+
+
+#. Applications screen
+msgid "Looking at the installed applications..."
+msgstr "Installierte Anwendungen werden durchgesehen …"
+
+msgid "No Chromium-based applications found."
+msgstr "Keine Chromium-basierten Anwendungen gefunden."
+
+msgid "Anything not identified is left alone until it is turned on here."
+msgstr "Nicht erkannte Anwendungen bleiben unangetastet, bis sie hier eingeschaltet werden."
+
+msgid "Autoscroll is off - this is what would be covered."
+msgstr "Autoscroll ist aus – das hier wäre abgedeckt."
+
+msgid "Up/Down select - Space turns one on or off - q goes back"
+msgstr "Hoch/Runter wählt – Leertaste schaltet einzeln ein oder aus – q geht zurück"
+
+
+#. Results
+msgid "Autoscroll is on for %d applications."
+msgstr "Autoscroll ist für %d Anwendungen an."
+
+msgid "Applications that are already running pick this up when they are restarted."
+msgstr "Bereits laufende Anwendungen übernehmen das nach einem Neustart."
+
+msgid "Could not start the watcher for newly installed applications."
+msgstr "Die Überwachung neu installierter Anwendungen konnte nicht gestartet werden."
+
+msgid "No systemd user session - newly installed applications will not be picked up on their own."
+msgstr "Keine systemd-Benutzersitzung – neu installierte Anwendungen werden nicht von selbst erfasst."
+
+msgid "Autoscroll is off and everything that was changed has been put back."
+msgstr "Autoscroll ist aus, alle Änderungen wurden zurückgenommen."
+
+msgid "Autoscroll is off. Turn it on first."
+msgstr "Autoscroll ist aus. Erst einschalten."
+
+msgid "Applied again to %d applications."
+msgstr "Erneut auf %d Anwendungen angewendet."
+
+msgid "Applied to %d applications."
+msgstr "Auf %d Anwendungen angewendet."
+
+msgid "Already applied to %d applications."
+msgstr "Bereits auf %d Anwendungen angewendet."
+
+msgid "Steam starts its interface in a way this version cannot change without Steam noticing; leaving it alone."
+msgstr "Steam startet seine Oberfläche auf eine Art, die diese Version nicht ändern kann, ohne dass Steam es merkt; Steam bleibt unangetastet."
+
+msgid "Steam's interface cannot be given the flag without leaving a file Steam would reinstall; the change has been taken back."
+msgstr "Steams Oberfläche lässt sich das Flag nicht geben, ohne eine Datei zu hinterlassen, die Steam neu installieren würde; die Änderung wurde zurückgenommen."
+
+msgid "Middle click stops pasting at the next login."
+msgstr "Mittelklick fügt ab der nächsten Anmeldung nichts mehr ein."
+
+
+#. Help
+msgid "Usage: middleclick-autoscroll [command]"
+msgstr "Aufruf: middleclick-autoscroll [Befehl]"
+
+msgid "Commands:"
+msgstr "Befehle:"
+
+msgid "Turn autoscroll on"
+msgstr "Autoscroll einschalten"
+
+msgid "Turn it off and put everything back"
+msgstr "Ausschalten und alles zurücknehmen"
+
+msgid "Apply to anything installed since the last run"
+msgstr "Auf alles anwenden, was seit dem letzten Lauf dazugekommen ist"
+
+msgid "Take everything back and apply it again"
+msgstr "Alles zurücknehmen und neu anwenden"
+
+msgid "Show what is covered"
+msgstr "Anzeigen, was abgedeckt ist"
+
+msgid "List every application that was found"
+msgstr "Alle gefundenen Anwendungen auflisten"
+
+msgid "Show this help"
+msgstr "Diese Hilfe anzeigen"
+
+msgid "Show the version"
+msgstr "Version anzeigen"
+
+msgid "Without a command an interactive menu is shown."
+msgstr "Ohne Befehl wird ein interaktives Menü angezeigt."
+
+msgid "Unknown command: %s"
+msgstr "Unbekannter Befehl: %s"
+
+
+#. Time
+msgid "never"
+msgstr "nie"
+
+msgid "just now"
+msgstr "gerade eben"
+
+msgid "%d minutes ago"
+msgstr "vor %d Minuten"
+
+msgid "%d hours ago"
+msgstr "vor %d Stunden"
+
+msgid "%d days ago"
+msgstr "vor %d Tagen"

po/middleclick-autoscroll.pot

@@ -0,0 +1,244 @@
+# Translation template for middleclick-autoscroll.
+# Copyright (C) 2026 Felitendo
+# This file is distributed under the same license as middleclick-autoscroll.
+#
+msgid ""
+msgstr ""
+"Project-Id-Version: middleclick-autoscroll 1.0.3\n"
+"Report-Msgid-Bugs-To: https://github.com/Felitendo/middleclick-autoscroll/issues\n"
+"POT-Creation-Date: 2026-08-16 00:00+0200\n"
+"PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
+"Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
+"Language-Team: LANGUAGE <LL@li.org>\n"
+"Language: \n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=UTF-8\n"
+"Content-Transfer-Encoding: 8bit\n"
+
+#. Status labels
+msgid "ON"
+msgstr ""
+
+msgid "OFF"
+msgstr ""
+
+msgid "on"
+msgstr ""
+
+msgid "off"
+msgstr ""
+
+msgid "(none)"
+msgstr ""
+
+msgid "flag file"
+msgstr ""
+
+msgid "launcher"
+msgstr ""
+
+msgid "cannot tell"
+msgstr ""
+
+msgid "not patched yet"
+msgstr ""
+
+
+#. Status block
+msgid "Autoscroll"
+msgstr ""
+
+msgid "Applications covered"
+msgstr ""
+
+msgid "%d of %d"
+msgstr ""
+
+msgid "Not identified"
+msgstr ""
+
+msgid "%d - see the applications list"
+msgstr ""
+
+msgid "Steam"
+msgstr ""
+
+msgid "Middle-click paste"
+msgstr ""
+
+msgid "New applications"
+msgstr ""
+
+msgid "Last applied"
+msgstr ""
+
+msgid "Applications pick this up the next time they are started."
+msgstr ""
+
+
+#. Menu
+msgid "Turn autoscroll on or off"
+msgstr ""
+
+msgid "Re-apply everything"
+msgstr ""
+
+msgid "Applications"
+msgstr ""
+
+msgid "Settings"
+msgstr ""
+
+msgid "Quit"
+msgstr ""
+
+msgid "Press any key to continue..."
+msgstr ""
+
+
+#. Settings
+msgid "Electron and CEF applications"
+msgstr ""
+
+msgid "Chromium-based browsers"
+msgstr ""
+
+msgid "Flatpak applications"
+msgstr ""
+
+msgid "Snap applications"
+msgstr ""
+
+msgid "Programs that start themselves at login"
+msgstr ""
+
+msgid "Spotify"
+msgstr ""
+
+msgid "Turn off KDE's middle-click paste"
+msgstr ""
+
+msgid "Apply to newly installed applications"
+msgstr ""
+
+msgid "Additional Chromium arguments"
+msgstr ""
+
+msgid "Up/Down select - Space or Right changes - q goes back"
+msgstr ""
+
+msgid "Arguments separated by spaces, empty for none:"
+msgstr ""
+
+msgid "Could not save the setting."
+msgstr ""
+
+
+#. Applications screen
+msgid "Looking at the installed applications..."
+msgstr ""
+
+msgid "No Chromium-based applications found."
+msgstr ""
+
+msgid "Anything not identified is left alone until it is turned on here."
+msgstr ""
+
+msgid "Autoscroll is off - this is what would be covered."
+msgstr ""
+
+msgid "Up/Down select - Space turns one on or off - q goes back"
+msgstr ""
+
+
+#. Results
+msgid "Autoscroll is on for %d applications."
+msgstr ""
+
+msgid "Applications that are already running pick this up when they are restarted."
+msgstr ""
+
+msgid "Could not start the watcher for newly installed applications."
+msgstr ""
+
+msgid "No systemd user session - newly installed applications will not be picked up on their own."
+msgstr ""
+
+msgid "Autoscroll is off and everything that was changed has been put back."
+msgstr ""
+
+msgid "Autoscroll is off. Turn it on first."
+msgstr ""
+
+msgid "Applied again to %d applications."
+msgstr ""
+
+msgid "Applied to %d applications."
+msgstr ""
+
+msgid "Already applied to %d applications."
+msgstr ""
+
+msgid "Steam starts its interface in a way this version cannot change without Steam noticing; leaving it alone."
+msgstr ""
+
+msgid "Steam's interface cannot be given the flag without leaving a file Steam would reinstall; the change has been taken back."
+msgstr ""
+
+msgid "Middle click stops pasting at the next login."
+msgstr ""
+
+
+#. Help
+msgid "Usage: middleclick-autoscroll [command]"
+msgstr ""
+
+msgid "Commands:"
+msgstr ""
+
+msgid "Turn autoscroll on"
+msgstr ""
+
+msgid "Turn it off and put everything back"
+msgstr ""
+
+msgid "Apply to anything installed since the last run"
+msgstr ""
+
+msgid "Take everything back and apply it again"
+msgstr ""
+
+msgid "Show what is covered"
+msgstr ""
+
+msgid "List every application that was found"
+msgstr ""
+
+msgid "Show this help"
+msgstr ""
+
+msgid "Show the version"
+msgstr ""
+
+msgid "Without a command an interactive menu is shown."
+msgstr ""
+
+msgid "Unknown command: %s"
+msgstr ""
+
+
+#. Time
+msgid "never"
+msgstr ""
+
+msgid "just now"
+msgstr ""
+
+msgid "%d minutes ago"
+msgstr ""
+
+msgid "%d hours ago"
+msgstr ""
+
+msgid "%d days ago"
+msgstr ""

res/systemd/middleclick-autoscroll.path

@@ -0,0 +1,43 @@
+[Unit]
+Description=Watch for newly installed Chromium-based applications
+Documentation=man:middleclick-autoscroll(1)
+
+[Path]
+# Every way an application can turn up: a package, a Flatpak, a snap, something
+# installed by hand. Watching where the launchers land means there is no hook
+# to write per package manager - pacman, apt, dnf, zypper, flatpak, snapd and
+# an AppImage manager all end up here.
+#
+# A directory that does not exist on this system costs nothing: systemd watches
+# the nearest parent that does and picks the path up when it appears.
+PathModified=/usr/share/applications
+PathModified=/usr/local/share/applications
+PathModified=%h/.local/share/applications
+PathModified=%h/.config/autostart
+PathModified=/var/lib/flatpak/exports/share/applications
+PathModified=%h/.local/share/flatpak/exports/share/applications
+PathModified=/var/lib/snapd/desktop/applications
+
+# NixOS and Guix build the search path out of profiles rather than /usr.
+PathModified=/run/current-system/sw/share/applications
+PathModified=%h/.nix-profile/share/applications
+PathModified=%h/.guix-profile/share/applications
+
+# The desktop folder is watched too - Steam writes a shortcut there for every
+# game somebody asks for one, and starting a game is a Steam start - but its
+# name is translated and cannot be written down here. `enable` adds it in a
+# drop-in, from the name this system uses.
+
+# Steam replaces the script that starts its interface on every client update,
+# which takes the patch with it. Where that installation lives depends on how
+# Steam was installed.
+PathChanged=%h/.local/share/Steam/ubuntu12_64/steamwebhelper_sniper_wrap.sh
+PathChanged=%h/.steam/debian-installation/ubuntu12_64/steamwebhelper_sniper_wrap.sh
+PathChanged=%h/.var/app/com.valvesoftware.Steam/.local/share/Steam/ubuntu12_64/steamwebhelper_sniper_wrap.sh
+PathChanged=%h/.var/app/com.valvesoftware.Steam/data/Steam/ubuntu12_64/steamwebhelper_sniper_wrap.sh
+PathChanged=%h/snap/steam/common/.local/share/Steam/ubuntu12_64/steamwebhelper_sniper_wrap.sh
+
+Unit=middleclick-autoscroll.service
+
+[Install]
+WantedBy=default.target

res/systemd/middleclick-autoscroll.service

@@ -0,0 +1,16 @@
+[Unit]
+Description=Apply middle-click autoscroll to Chromium-based applications
+Documentation=man:middleclick-autoscroll(1)
+
+[Service]
+Type=oneshot
+ExecStart=@BINDIR@/middleclick-autoscroll apply --quiet
+# Scanning binaries for their engine is the slow part, and it is cached; a run
+# that takes longer than this has found something pathological and should not
+# be left running at every login.
+TimeoutStartSec=180
+Nice=10
+IOSchedulingClass=idle
+
+[Install]
+WantedBy=default.target

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src/lib/apply.sh

@@ -0,0 +1,285 @@
+# shellcheck shell=bash
+#
+# Deciding what happens to each application, and doing it.
+#
+# The routing lives in mca_route and is used twice: once by mca_apply to patch
+# and once by the applications screen to show what would happen. Keeping it in
+# one function is what makes that screen trustworthy - it is not a description
+# of the behaviour, it is the behaviour.
+
+MCA_CHANGES=0
+MCA_ROUTES=()
+
+# mca_route <kind> <id> <program> [packaging]
+# What happens to one application, left in MCA_ROUTE:
+#   flags    - the launcher reads a flag file; write it there
+#   desktop  - no flag file; shadow or edit the desktop entry
+#   steam    - Steam's own two-part treatment
+#   unknown  - cannot tell what engine this is (an AppImage), so nothing is done
+#   off      - detected, but switched off
+#
+# Assigns rather than prints so the memo inside mca_has_flags_file survives:
+# from inside a command substitution it would be filled in a subshell and
+# thrown away, which is the whole point of having it.
+MCA_ROUTE=''
+
+mca_route() {
+	local kind="$1" id="$2" prog="$3" packaging="${4:-native}"
+
+	if [[ $kind == steam ]]; then
+		if mca_config_list_has Skip "$id" || [[ $CFG_STEAM != yes ]]; then
+			MCA_ROUTE=off
+		else
+			MCA_ROUTE=steam
+		fi
+		return
+	fi
+
+	if ! mca_kind_wanted "$kind" "$id" "$packaging"; then
+		[[ $kind == unknown ]] && MCA_ROUTE=unknown || MCA_ROUTE=off
+		return
+	fi
+
+	# A Flatpak or a snap carries its own copy of everything and sees none of
+	# the host's wrappers, so the desktop entry is the only way in.
+	if [[ $packaging != native ]]; then
+		MCA_ROUTE=desktop
+		return
+	fi
+
+	if mca_has_flags_file "$prog"; then
+		MCA_ROUTE=flags
+	else
+		MCA_ROUTE=desktop
+	fi
+}
+
+# mca_apply
+# Brings everything into line with the current settings. Safe to run as often
+# as it likes to be - it writes only what differs, which is what keeps the
+# watcher from chasing its own changes.
+mca_apply() {
+	local i id file prog kind packaging route steam_done=0
+
+	MCA_CHANGES=0
+	MCA_ROUTES=()
+	MCA_N_ON=0; MCA_N_OFF=0; MCA_N_UNKNOWN=0
+
+	mca_config_load
+
+	# An installation that was set up by a version whose answer was a different
+	# flag still has that flag where it put it, and nothing below would touch it
+	# again: a file that is already marked as patched is left alone. Taking
+	# everything back once, here, is what carries such an installation over.
+	if [[ "$(mca_state_read flag_scheme 1)" != "$MCA_FLAG_SCHEME" ]]; then
+		mca_revert_all
+	fi
+
+	mca_scan
+
+	for i in "${!MCA_IDS[@]}"; do
+		id="${MCA_IDS[i]}"
+		file="${MCA_FILES[i]}"
+		prog="${MCA_PROGS[i]}"
+		kind="${MCA_KINDS[i]}"
+		packaging="${MCA_PACKAGING[i]}"
+
+		mca_route "$kind" "$id" "$prog" "$packaging"
+		route="$MCA_ROUTE"
+		MCA_ROUTES[i]="$route"
+
+		case "$route" in
+			unknown) MCA_N_UNKNOWN=$(( MCA_N_UNKNOWN + 1 )) ;;
+			off)     MCA_N_OFF=$(( MCA_N_OFF + 1 )) ;;
+			*)       MCA_N_ON=$(( MCA_N_ON + 1 )) ;;
+		esac
+
+		case "$route" in
+			flags)
+				mca_flags_apply "$prog" "$kind" \
+					|| mca_desktop_apply "$id" "$file" "$(mca_flags "$kind")"
+				;;
+			desktop)
+				mca_desktop_apply "$id" "$file" "$(mca_flags "$kind")"
+				;;
+			steam)
+				# Nothing is done to the entry itself: what Steam needs is
+				# in its own installation, and the same patch serves every
+				# way of starting the client.
+				if (( ! steam_done )); then
+					mca_steam_apply
+					steam_done=1
+				fi
+				;;
+		esac
+	done
+
+	# Steam is worth patching even when its desktop entry is missing - a user
+	# who starts it from a script or a game launcher still gets the interface.
+	if [[ $CFG_STEAM == yes ]] && (( ! steam_done )) && mca_steam_installed; then
+		mca_steam_apply
+	fi
+
+	# Autostart entries. A Chromium application that starts itself at login
+	# points straight at its binary and never reads the entry in the menu, so
+	# Discord at login used to behave differently from Discord from the menu.
+	if [[ $CFG_AUTOSTART == yes ]]; then
+		mca_autostart_apply
+	fi
+
+	# Shortcuts on the desktop itself, which nothing above has seen: the XDG
+	# search path does not go there. Each entry is gated on its own, so there is
+	# nothing to check out here.
+	mca_shortcuts_apply
+
+	[[ $CFG_SPOTIFY == yes ]] && mca_spotify_apply
+
+	# Not about any one application: middle click goes on pasting everywhere
+	# else on the desktop, and KDE is the one desktop that can be told not to.
+	# See kde.sh.
+	[[ $CFG_PASTE == yes ]] && mca_kde_paste_apply
+
+	mca_prune_orphans
+
+	if (( MCA_CHANGES )) && mca_have update-desktop-database; then
+		update-desktop-database "$MCA_APPDIR" 2>/dev/null || true
+	fi
+
+	mca_state_write last_apply "$(date +%s)"
+	mca_state_write flag_scheme "$MCA_FLAG_SCHEME"
+	return 0
+}
+
+# mca_revert
+# Undoes every recorded change and forgets them.
+mca_revert() {
+	MCA_CHANGES=0
+	mca_revert_all
+
+	if (( MCA_CHANGES )) && mca_have update-desktop-database; then
+		update-desktop-database "$MCA_APPDIR" 2>/dev/null || true
+	fi
+
+	return 0
+}
+
+# ---------------------------------------------------------------------------
+# The watcher
+# ---------------------------------------------------------------------------
+# A systemd user path unit watching every directory a desktop entry can appear
+# in. That covers a package from whatever the distribution's package manager
+# is, a Flatpak, a snap, an AppImage registered by hand and a Steam client
+# update, without a hook per package manager.
+
+MCA_UNIT_PATH="middleclick-autoscroll.path"
+MCA_UNIT_SERVICE="middleclick-autoscroll.service"
+
+# The desktop folder is watched like every other directory an entry can turn up
+# in, but its name is translated and the unit that ships with the package
+# cannot know it. So that one path is written here, into a drop-in, from the
+# name this system actually uses.
+MCA_UNIT_DROPIN="${MCA_XDG_CONFIG}/systemd/user/${MCA_UNIT_PATH}.d"
+
+mca_watch_available() {
+	mca_have systemctl && [[ -n ${XDG_RUNTIME_DIR:-} || -S "/run/user/$(id -u)/bus" ]]
+}
+
+mca_watch_enabled() {
+	mca_watch_available || return 1
+	systemctl --user is-enabled --quiet "$MCA_UNIT_PATH" 2>/dev/null
+}
+
+# _mca_watch_dropin_write
+# Returns 0 when the drop-in changed and systemd has to be told, 1 when it was
+# already right - the same contract as mca_write_if_changed, and for the same
+# reason: the watcher runs after every desktop entry that appears anywhere on
+# the system, and a daemon-reload each time would be absurd.
+_mca_watch_dropin_write() {
+	local dir file="$MCA_UNIT_DROPIN/desktop.conf" content
+
+	dir="$(mca_desktop_folder)"
+	[[ -d $dir ]] || { _mca_watch_dropin_remove; return $?; }
+
+	# A per cent sign starts a specifier in a unit file and has to be doubled
+	# to mean itself. Rare in a folder name, fatal when it happens.
+	content="[Path]"$'\n'"PathModified=${dir//%/%%}"$'\n'
+
+	mca_write_if_changed "$file" "$content"
+}
+
+_mca_watch_dropin_remove() {
+	[[ -e "$MCA_UNIT_DROPIN/desktop.conf" ]] || return 1
+	rm -f -- "$MCA_UNIT_DROPIN/desktop.conf"
+	rmdir "$MCA_UNIT_DROPIN" 2>/dev/null || true
+	return 0
+}
+
+mca_watch_enable() {
+	mca_watch_available || return 1
+	_mca_watch_dropin_write
+	systemctl --user daemon-reload > /dev/null 2>&1 || true
+	systemctl --user enable --now "$MCA_UNIT_PATH" > /dev/null 2>&1 || return 1
+	systemctl --user enable "$MCA_UNIT_SERVICE" > /dev/null 2>&1 || true
+	return 0
+}
+
+# mca_watch_refresh
+# Keeps a running watcher in step with a desktop folder that has been renamed,
+# which is what a change of session language does to it.
+mca_watch_refresh() {
+	mca_watch_available || return 0
+	_mca_watch_dropin_write || return 0
+	systemctl --user daemon-reload > /dev/null 2>&1 || true
+	systemctl --user restart "$MCA_UNIT_PATH" > /dev/null 2>&1 || true
+	return 0
+}
+
+mca_watch_disable() {
+	mca_watch_available || return 0
+	systemctl --user disable --now "$MCA_UNIT_PATH" > /dev/null 2>&1 || true
+	systemctl --user disable "$MCA_UNIT_SERVICE" > /dev/null 2>&1 || true
+	_mca_watch_dropin_remove && systemctl --user daemon-reload > /dev/null 2>&1
+	return 0
+}
+
+# ---------------------------------------------------------------------------
+# Reporting
+# ---------------------------------------------------------------------------
+
+# mca_count_routes
+# Fills MCA_N_ON / MCA_N_OFF / MCA_N_UNKNOWN from a scan, without writing
+# anything. Used by the status block and the menu header.
+MCA_N_ON=0
+MCA_N_OFF=0
+MCA_N_UNKNOWN=0
+
+mca_count_routes() {
+	local i route
+
+	MCA_N_ON=0; MCA_N_OFF=0; MCA_N_UNKNOWN=0
+	MCA_ROUTES=()
+
+	for i in "${!MCA_IDS[@]}"; do
+		mca_route "${MCA_KINDS[i]}" "${MCA_IDS[i]}" "${MCA_PROGS[i]}" \
+			"${MCA_PACKAGING[i]}"
+		route="$MCA_ROUTE"
+		MCA_ROUTES[i]="$route"
+		case "$route" in
+			unknown) MCA_N_UNKNOWN=$(( MCA_N_UNKNOWN + 1 )) ;;
+			off)     MCA_N_OFF=$(( MCA_N_OFF + 1 )) ;;
+			*)       MCA_N_ON=$(( MCA_N_ON + 1 )) ;;
+		esac
+	done
+}
+
+# mca_route_label <route>
+mca_route_label() {
+	case "$1" in
+		flags)   mca_msg "flag file" ;;
+		desktop) mca_msg "launcher" ;;
+		steam)   mca_msg "Steam" ;;
+		unknown) mca_msg "cannot tell" ;;
+		*)       mca_msg "off" ;;
+	esac
+	printf '\n'
+}

src/lib/common.sh

@@ -0,0 +1,378 @@
+# shellcheck shell=bash
+#
+# Paths, translations, output helpers and the change ledger.
+#
+# Everything here runs unprivileged. This tool only ever writes inside the
+# user's own home - flag files, desktop entries, Steam's own scripts - so there
+# is no system state to guard and nothing that needs root.
+
+MCA_VERSION="@VERSION@"
+MCA_NAME="middleclick-autoscroll"
+MCA_PRETTY="Middle-Click Autoscroll"
+
+# The whole point of the package. Blink implements Windows-style autoscroll
+# behind a runtime flag that Chromium does not turn on for Linux, because
+# middle click is taken by primary-selection paste there.
+#
+# There are two ways to ask for that flag, and which one is right depends on
+# what is being started:
+#
+#   --enable-blink-features=MiddleClickAutoscroll is the one that works
+#   everywhere, and the only one that works in the Chromium versions embedded
+#   applications ship - Steam's CEF, an Electron a few years old, anything
+#   before Chromium 124. A browser started with it puts a yellow bar above the
+#   page saying an unsupported command line flag is in use, because Chromium
+#   keeps a list of flags worth warning about and this is on it.
+#
+#   --enable-features=MiddleClickAutoscroll is not on that list, so a browser
+#   started with it says nothing. Blink generates a feature of the same name
+#   for every one of its runtime flags, which is what makes the two the same
+#   request - but only since Chromium 124. Before that the name means nothing
+#   and is ignored without a word.
+#
+# So a browser, which is the only thing that shows the bar and the one thing
+# that keeps itself up to date, is given the quiet one; everything else keeps
+# the one that always works.
+MCA_FLAG="--enable-blink-features=MiddleClickAutoscroll"
+
+# Two browsers do not answer to the Chromium name. Helium ships the feature
+# under its own name and sets the runtime flag from that alone. Brave takes
+# the generated feature away and switches the flag on from one of its own,
+# spelled MiddelButtonClickAutoscroll - the typo is in Brave's source, and the
+# correct spelling does nothing. So browsers are asked for all three. A name a
+# browser does not know is ignored, which is what makes one list safe to hand
+# to all of them.
+MCA_BROWSER_FLAG="--enable-features=MiddleClickAutoscroll,HeliumMiddleClickAutoscroll,MiddelButtonClickAutoscroll"
+
+# The feature names on their own, for merging into a list that an application
+# (or the user) already carries, and for taking them back out again.
+MCA_FEATURE="MiddleClickAutoscroll"
+MCA_BROWSER_FEATURES="MiddleClickAutoscroll,HeliumMiddleClickAutoscroll,MiddelButtonClickAutoscroll"
+
+# Bumped when the flags above change, and when what gets written where does.
+# An installation that was set up by a version with a different answer is taken
+# back and done again once, because a file that is already patched is otherwise
+# left alone. See mca_apply.
+#
+# 3 is what takes -noverifyfiles back out of the Steam entries an older version
+# put it in.
+#
+# 4 adds Brave's name to the browser list, which an entry edited in place would
+# otherwise never get.
+MCA_FLAG_SCHEME=4
+
+MCA_LIBDIR="${MCA_LIBDIR:-@LIBDIR@}"
+MCA_LOCALEDIR="${MCA_LOCALEDIR:-@LOCALEDIR@}"
+
+MCA_XDG_CONFIG="${XDG_CONFIG_HOME:-$HOME/.config}"
+MCA_XDG_DATA="${XDG_DATA_HOME:-$HOME/.local/share}"
+MCA_XDG_STATE="${XDG_STATE_HOME:-$HOME/.local/state}"
+MCA_XDG_CACHE="${XDG_CACHE_HOME:-$HOME/.cache}"
+
+MCA_CONFDIR="${MCA_CONFDIR:-${MCA_XDG_CONFIG}/${MCA_NAME}}"
+MCA_CONFIG="${MCA_CONFIG:-${MCA_CONFDIR}/config}"
+MCA_STATEDIR="${MCA_STATEDIR:-${MCA_XDG_STATE}/${MCA_NAME}}"
+MCA_CACHEDIR="${MCA_CACHEDIR:-${MCA_XDG_CACHE}/${MCA_NAME}}"
+
+# Where generated desktop entries go. A file here shadows the one with the same
+# name in /usr/share/applications, which is how an application gets extra
+# command line arguments without touching a file the package manager owns.
+MCA_APPDIR="${MCA_XDG_DATA}/applications"
+
+# Copies of every file that is edited in place rather than shadowed.
+MCA_BACKUPDIR="${MCA_STATEDIR}/backup"
+
+# One line per change, so `revert` can undo exactly what was done and nothing
+# else. See mca_ledger_add.
+MCA_LEDGER="${MCA_STATEDIR}/ledger"
+
+# The folder the desktop itself shows. Nothing in the XDG search path looks at
+# it, so an entry that lives only there is invisible to a scan - and a game
+# shortcut dragged onto the desktop is exactly that.
+#
+# Its name is translated: Schreibtisch, Bureau, Escritorio. The name in use is
+# in the file xdg-user-dirs writes, so it is read rather than guessed, and
+# ~/Desktop is only the fallback for a system that has no such file.
+mca_desktop_folder() {
+	local file="$MCA_XDG_CONFIG/user-dirs.dirs" line dir=''
+
+	if [[ -r $file ]]; then
+		while IFS= read -r line; do
+			[[ $line == XDG_DESKTOP_DIR=* ]] || continue
+			dir="${line#XDG_DESKTOP_DIR=}"
+			dir="${dir%\"}"; dir="${dir#\"}"
+		done < "$file"
+		dir="${dir/#\$HOME/$HOME}"
+	fi
+
+	[[ $dir == /* ]] || dir="$HOME/Desktop"
+	printf '%s\n' "${dir%/}"
+}
+
+# ---------------------------------------------------------------------------
+# Translations
+# ---------------------------------------------------------------------------
+
+export TEXTDOMAIN="middleclick-autoscroll"
+export TEXTDOMAINDIR="${MCA_LOCALEDIR}"
+
+mca_ui_locale() {
+	local l="${MCA_UI_LOCALE:-}"
+
+	if [[ -z $l ]]; then
+		l="${LC_ALL:-}"
+		[[ -z $l ]] && l="${LC_MESSAGES:-}"
+		[[ -z $l ]] && l="${LANG:-}"
+	fi
+
+	# systemd writes /etc/locale.conf and most distributions use it; Debian and
+	# Ubuntu keep the same LANG= line in /etc/default/locale instead.
+	if [[ -z $l ]]; then
+		local f
+		for f in /etc/locale.conf /etc/default/locale; do
+			[[ -r $f ]] || continue
+			l="$(sed -n 's/^LANG=//p' "$f" | tr -d '"' | head -n1)"
+			[[ -n $l ]] && break
+		done
+	fi
+
+	printf '%s\n' "${l:-C}"
+}
+
+# Every gettext lookup is a fork and the settings screen redraws a screenful of
+# labels per keypress, so results are memoized.
+declare -A MCA_MSG_CACHE=()
+
+MCA_MSG_RESULT=''
+
+# mca_msg_into <locale> <msgid>
+# Plain lookup with the result in MCA_MSG_RESULT and no printf formatting, for
+# callers that would otherwise pay a fork per label per frame.
+mca_msg_into() {
+	local locale="$1" msgid="$2" cachekey
+	cachekey="${locale}"$'\x1f'"${msgid}"
+
+	if [[ -n ${MCA_MSG_CACHE[$cachekey]+set} ]]; then
+		MCA_MSG_RESULT="${MCA_MSG_CACHE[$cachekey]}"
+		return 0
+	fi
+
+	MCA_MSG_RESULT="$(LC_ALL="$locale" LANGUAGE="${locale%%.*}" gettext -- "$msgid" 2>/dev/null)"
+	[[ -n $MCA_MSG_RESULT ]] || MCA_MSG_RESULT="$msgid"
+	MCA_MSG_CACHE[$cachekey]="$MCA_MSG_RESULT"
+	return 0
+}
+
+# mca_msg_in <locale> <msgid> [printf args...]
+mca_msg_in() {
+	local locale="$1" msgid="$2" translated cachekey
+	shift 2
+
+	cachekey="${locale}"$'\x1f'"${msgid}"
+	if [[ -n ${MCA_MSG_CACHE[$cachekey]+set} ]]; then
+		translated="${MCA_MSG_CACHE[$cachekey]}"
+	else
+		translated="$(LC_ALL="$locale" LANGUAGE="${locale%%.*}" gettext -- "$msgid" 2>/dev/null)"
+		[[ -n $translated ]] || translated="$msgid"
+		MCA_MSG_CACHE[$cachekey]="$translated"
+	fi
+
+	# With no arguments the message is plain text, not a format string. Feeding
+	# it to printf anyway would turn a literal percent sign in a translation
+	# into an invalid conversion.
+	if (( $# == 0 )); then
+		printf '%s' "$translated"
+		return
+	fi
+
+	# shellcheck disable=SC2059  # the format string is the translated message
+	printf -- "$translated" "$@"
+}
+
+# mca_msg <msgid> [printf args...]
+mca_msg() { mca_msg_in "$(mca_ui_locale)" "$@"; }
+
+# ---------------------------------------------------------------------------
+# Output
+# ---------------------------------------------------------------------------
+
+# Decided once, while stdout is still whatever the process was started with:
+# testing -t 1 at the point of use is wrong for anything called through $(...),
+# which sees a pipe and would conclude nobody is watching.
+MCA_INTERACTIVE=''
+[[ -t 1 ]] && MCA_INTERACTIVE=1
+
+if [[ -n $MCA_INTERACTIVE && -z ${NO_COLOR:-} ]]; then
+	MCA_C_RESET=$'\033[0m'
+	MCA_C_BOLD=$'\033[1m'
+	MCA_C_DIM=$'\033[2m'
+	MCA_C_BLUE=$'\033[38;2;23;147;209m'
+	MCA_C_GREEN=$'\033[32m'
+	MCA_C_YELLOW=$'\033[33m'
+	MCA_C_RED=$'\033[31m'
+else
+	MCA_C_RESET='' MCA_C_BOLD='' MCA_C_DIM='' MCA_C_BLUE=''
+	MCA_C_GREEN='' MCA_C_YELLOW='' MCA_C_RED=''
+fi
+
+# Set by mca_bad and mca_note. The menu redraws straight after an action, which
+# would wipe the screen; this marks that something was printed the user still
+# has to read. A plain success needs no acknowledgement - the status block at
+# the top of the menu already shows the new state.
+MCA_UI_NEEDS_ACK=''
+
+# --quiet silences progress chatter; errors still go to stderr. Used by the
+# systemd unit, which has no terminal and logs to the journal anyway.
+MCA_QUIET=''
+
+mca_say()  { [[ -n $MCA_QUIET ]] || printf '%s\n' "$*"; }
+mca_head() { printf '\n%s%s%s\n\n' "$MCA_C_BOLD$MCA_C_BLUE" "$*" "$MCA_C_RESET"; }
+mca_ok()   { [[ -n $MCA_QUIET ]] || printf '%s✔%s %s\n' "$MCA_C_GREEN" "$MCA_C_RESET" "$*"; }
+mca_bad()  { MCA_UI_NEEDS_ACK=1; printf '%s✘%s %s\n' "$MCA_C_RED" "$MCA_C_RESET" "$*" >&2; }
+mca_note() { MCA_UI_NEEDS_ACK=1; [[ -n $MCA_QUIET ]] || printf '%s•%s %s\n' "$MCA_C_DIM" "$MCA_C_RESET" "$*"; }
+
+mca_have() { command -v "$1" > /dev/null 2>&1; }
+
+# Human-readable "x minutes ago" for a unix timestamp. Empty input yields the
+# translated "never".
+mca_time_ago() {
+	local ts="$1" now delta
+
+	[[ $ts =~ ^[0-9]+$ ]] || { mca_msg "never"; printf '\n'; return; }
+
+	now="$(date +%s)"
+	delta=$(( now - ts ))
+	(( delta < 0 )) && delta=0
+
+	if   (( delta < 60 ));    then mca_msg "just now"
+	elif (( delta < 3600 ));  then mca_msg "%d minutes ago" "$(( delta / 60 ))"
+	elif (( delta < 86400 )); then mca_msg "%d hours ago" "$(( delta / 3600 ))"
+	else                           mca_msg "%d days ago" "$(( delta / 86400 ))"
+	fi
+	printf '\n'
+}
+
+# ---------------------------------------------------------------------------
+# State
+# ---------------------------------------------------------------------------
+
+mca_state_read() {
+	local key="$1" default="${2:-}"
+	if [[ -r "$MCA_STATEDIR/$key" ]]; then
+		cat "$MCA_STATEDIR/$key"
+	else
+		printf '%s\n' "$default"
+	fi
+}
+
+mca_state_write() {
+	local key="$1"
+	shift
+	mkdir -p "$MCA_STATEDIR" 2>/dev/null || return 1
+	printf '%s\n' "$*" > "$MCA_STATEDIR/$key"
+}
+
+# ---------------------------------------------------------------------------
+# The change ledger
+# ---------------------------------------------------------------------------
+# Reverting by pattern - "delete every desktop entry that mentions the flag" -
+# would also delete entries the user wrote by hand. So every change is recorded
+# instead, and `revert` replays the ledger backwards.
+#
+# Format, tab separated:
+#   <kind> <path> <detail>
+#
+#   shadow  <generated desktop entry>   <source entry it was generated from>
+#   inplace <edited file>               <basename of its backup copy>
+#   flags   <flag file>                 created | appended | merged
+#   kwin    <kwinrc>                    what EnablePrimarySelection said before
+#
+# The kinds differ in how they are undone: a backup is restored wholesale, a
+# flag file only loses the one line that was added to it, and kwinrc gets one
+# key written back - it is a file KDE writes to itself, and putting a whole
+# copy of it back would take everything else settled since with it.
+
+mca_ledger_add() {
+	local kind="$1" path="$2" detail="${3:-}"
+	mkdir -p "$MCA_STATEDIR" 2>/dev/null || return 1
+
+	# Never record the same path twice: applying repeatedly is normal (the path
+	# unit fires on every desktop file that appears) and the ledger has to stay
+	# a set, not a log.
+	mca_ledger_forget "$path"
+	printf '%s\t%s\t%s\n' "$kind" "$path" "$detail" >> "$MCA_LEDGER"
+}
+
+# mca_ledger_has <path>
+# Whether the ledger still knows about that file. Worth asking because the copy
+# kept beside it is named after the path and outlives a ledger that was lost or
+# truncated: a file nothing has a record of any more is one nothing would ever
+# look at again.
+mca_ledger_has() {
+	[[ -f $MCA_LEDGER ]] || return 1
+	awk -F'\t' -v p="$1" '$2 == p { found = 1 } END { exit !found }' "$MCA_LEDGER"
+}
+
+# mca_ledger_detail <path>
+# The third column of that file's line, empty when the ledger has none. What it
+# means is the kind's business; for `kwin` it is the value to put back.
+mca_ledger_detail() {
+	[[ -f $MCA_LEDGER ]] || return 1
+	awk -F'\t' -v p="$1" '$2 == p { d = $3 } END { if (!length(d)) exit 1; print d }' \
+		"$MCA_LEDGER"
+}
+
+mca_ledger_forget() {
+	local path="$1" tmp
+	[[ -f $MCA_LEDGER ]] || return 0
+
+	tmp="$(mktemp "${MCA_LEDGER}.XXXXXX")" || return 1
+	awk -F'\t' -v p="$path" '$2 != p' "$MCA_LEDGER" > "$tmp" 2>/dev/null \
+		&& mv -f "$tmp" "$MCA_LEDGER" || rm -f "$tmp"
+	return 0
+}
+
+
+# mca_backup_name <file>
+# The name a backup copy of that file is stored under. Derived from the path
+# rather than remembered, so a caller can ask whether a file has been backed up
+# before without reading the ledger.
+mca_backup_name() {
+	printf '%s' "$1" | sed 's|/|%|g'
+}
+
+# mca_backup <file>
+# Copies a file aside before it is edited in place, and prints the name the
+# copy was stored under. Existing backups are never overwritten: the first copy
+# is the pristine one, and a second apply must not replace it with an already
+# patched version.
+mca_backup() {
+	local file="$1" name
+	name="$(mca_backup_name "$file")"
+
+	mkdir -p "$MCA_BACKUPDIR" 2>/dev/null || return 1
+	if [[ ! -e "$MCA_BACKUPDIR/$name" ]]; then
+		cp -p -- "$file" "$MCA_BACKUPDIR/$name" 2>/dev/null || return 1
+	fi
+	printf '%s\n' "$name"
+}
+
+# mca_write_if_changed <path> <content>
+# Writing a file that is already correct would touch its mtime, and the systemd
+# path unit watches these directories: an unconditional write would retrigger
+# the service, which would write again, forever.
+mca_write_if_changed() {
+	local path="$1" content="$2" current=''
+
+	[[ -r $path ]] && current="$(< "$path")"
+
+	# $(< file) drops trailing newlines and callers pass content that ends in
+	# one, so both sides are trimmed before comparing. Getting this wrong makes
+	# every file look changed on every run, which is exactly the feedback loop
+	# this function exists to prevent.
+	[[ "${current%"${current##*[!$'\n']}"}" == "${content%"${content##*[!$'\n']}"}" ]] && return 1
+
+	mkdir -p "$(dirname "$path")" 2>/dev/null || return 2
+	printf '%s' "$content" > "$path" || return 2
+	return 0
+}

src/lib/config.sh

@@ -0,0 +1,172 @@
+# shellcheck shell=bash
+#
+# Reading and writing ~/.config/middleclick-autoscroll/config.
+#
+# The file exists so the tool has somewhere to remember what it was told; it is
+# not meant to be edited. Every option it holds is reachable from the interface,
+# which is why there is no commented template shipped anywhere and no reference
+# to the path in the interface itself.
+#
+# It is parsed rather than sourced. One "Key=Value" per line, '#' comments.
+
+MCA_CONFIG_CACHE=''
+MCA_CONFIG_CACHED=0
+
+_mca_config_slurp() {
+	(( MCA_CONFIG_CACHED )) && return 0
+	MCA_CONFIG_CACHE=''
+	[[ -r $MCA_CONFIG ]] && MCA_CONFIG_CACHE="$(< "$MCA_CONFIG")"
+	MCA_CONFIG_CACHED=1
+	return 0
+}
+
+# _mca_config_lookup <Key> [default]
+# Result in MCA_CONFIG_VALUE. Assigning rather than printing matters on the
+# settings screen, which reads every key on every frame: a command substitution
+# there is a fork, and forks are the whole cost of a redraw.
+MCA_CONFIG_VALUE=''
+
+_mca_config_lookup() {
+	local key="$1" default="${2:-}" val='' line
+
+	MCA_CONFIG_VALUE="$default"
+	[[ -r $MCA_CONFIG ]] || return 0
+	_mca_config_slurp
+
+	while IFS= read -r line; do
+		[[ $line == *"$key"* ]] || continue
+		[[ $line =~ ^[[:space:]]*"$key"[[:space:]]*=(.*)$ ]] || continue
+		val="${BASH_REMATCH[1]}"
+	done <<< "$MCA_CONFIG_CACHE"
+
+	val="${val%%#*}"
+	val="${val#"${val%%[![:space:]]*}"}"
+	val="${val%"${val##*[![:space:]]}"}"
+	val="${val%\"}"
+	val="${val#\"}"
+
+	[[ -n $val ]] && MCA_CONFIG_VALUE="$val"
+	return 0
+}
+
+# mca_config_get <Key> [default]
+mca_config_get() {
+	_mca_config_lookup "$@"
+	printf '%s\n' "$MCA_CONFIG_VALUE"
+}
+
+# mca_config_bool <Key> <default: yes|no>
+mca_config_bool() {
+	local val
+	val="$(mca_config_get "$1" "$2")"
+	case "${val,,}" in
+		yes|y|true|1|on|enabled) return 0 ;;
+		*) return 1 ;;
+	esac
+}
+
+# mca_config_set <Key> <Value>
+mca_config_set() {
+	local key="$1" value="$2" tmp
+
+	if [[ ! -e $MCA_CONFIG ]]; then
+		mkdir -p "$(dirname "$MCA_CONFIG")" || return 1
+		{
+			printf '# %s\n' "$MCA_PRETTY"
+			printf '#\n'
+			printf '# Written by `%s`. Nothing here needs editing by hand -\n' "$MCA_NAME"
+			printf '# every option is reachable from `%s` itself.\n' "$MCA_NAME"
+		} > "$MCA_CONFIG" || return 1
+	fi
+	[[ -w $MCA_CONFIG ]] || return 1
+
+	tmp="$(mktemp "${MCA_CONFIG}.XXXXXX")" || return 1
+	chmod --reference="$MCA_CONFIG" "$tmp" 2>/dev/null || chmod 0644 "$tmp"
+
+	if grep -qE "^[[:space:]]*#?[[:space:]]*${key}[[:space:]]*=" "$MCA_CONFIG"; then
+		awk -v key="$key" -v value="$value" '
+			!done && $0 ~ "^[[:space:]]*#?[[:space:]]*" key "[[:space:]]*=" {
+				print key "=" value; done = 1; next
+			}
+			# drop any further occurrences so the file cannot grow duplicates
+			$0 ~ "^[[:space:]]*" key "[[:space:]]*=" { next }
+			{ print }
+		' "$MCA_CONFIG" > "$tmp" || { rm -f "$tmp"; return 1; }
+	else
+		cat "$MCA_CONFIG" > "$tmp" || { rm -f "$tmp"; return 1; }
+		printf '%s=%s\n' "$key" "$value" >> "$tmp"
+	fi
+
+	mv -f "$tmp" "$MCA_CONFIG"
+	MCA_CONFIG_CACHED=0
+}
+
+# mca_config_list_has <Key> <item>
+# The per-application overrides are stored as space separated lists.
+mca_config_list_has() {
+	local list item="$2" entry
+	list="$(mca_config_get "$1" '')"
+	for entry in $list; do
+		[[ $entry == "$item" ]] && return 0
+	done
+	return 1
+}
+
+# mca_config_list_add <Key> <item> / mca_config_list_del <Key> <item>
+mca_config_list_add() {
+	local key="$1" item="$2" list
+	mca_config_list_has "$key" "$item" && return 0
+	list="$(mca_config_get "$key" '')"
+	mca_config_set "$key" "${list:+$list }$item"
+}
+
+mca_config_list_del() {
+	local key="$1" item="$2" list entry out=''
+	list="$(mca_config_get "$key" '')"
+	for entry in $list; do
+		[[ $entry == "$item" ]] && continue
+		out="${out:+$out }$entry"
+	done
+	mca_config_set "$key" "$out"
+}
+
+# ---------------------------------------------------------------------------
+# Resolved settings
+# ---------------------------------------------------------------------------
+
+mca_config_load() {
+	CFG_ENABLED=no;    mca_config_bool Enabled          no  && CFG_ENABLED=yes
+	CFG_APPS=no;       mca_config_bool PatchApps        yes && CFG_APPS=yes
+	CFG_BROWSERS=no;   mca_config_bool PatchBrowsers    yes && CFG_BROWSERS=yes
+	CFG_FLATPAK=no;    mca_config_bool PatchFlatpak     yes && CFG_FLATPAK=yes
+	CFG_SNAP=no;       mca_config_bool PatchSnap        yes && CFG_SNAP=yes
+	CFG_AUTOSTART=no;  mca_config_bool PatchAutostart   yes && CFG_AUTOSTART=yes
+	CFG_STEAM=no;      mca_config_bool PatchSteam       yes && CFG_STEAM=yes
+	CFG_SPOTIFY=no;    mca_config_bool PatchSpotify     yes && CFG_SPOTIFY=yes
+	CFG_WATCH=no;      mca_config_bool WatchNewApps     yes && CFG_WATCH=yes
+	CFG_PASTE=no;      mca_config_bool DisablePaste     yes && CFG_PASTE=yes
+
+	CFG_EXTRA_FLAGS="$(mca_config_get ExtraFlags '')"
+
+	# Applications the user turned on or off by hand on the applications
+	# screen, by desktop file id. Include wins over detection, Skip wins over
+	# everything.
+	CFG_INCLUDE="$(mca_config_get Include '')"
+	CFG_SKIP="$(mca_config_get Skip '')"
+}
+
+# mca_flags [kind]
+# The full argument string that gets injected. Kept in one place so the flag
+# file writer and the desktop entry writer cannot drift apart.
+#
+# A browser gets the flag that leaves it without a warning bar; everything else
+# gets the one that works in every Chromium there is. See MCA_FLAG.
+mca_flags() {
+	if [[ ${1:-app} == browser ]]; then
+		printf '%s' "$MCA_BROWSER_FLAG"
+	else
+		printf '%s' "$MCA_FLAG"
+	fi
+	[[ -n ${CFG_EXTRA_FLAGS:-} ]] && printf ' %s' "$CFG_EXTRA_FLAGS"
+	printf '\n'
+}

src/lib/kde.sh

@@ -0,0 +1,167 @@
+# shellcheck shell=bash
+#
+# KDE's middle-click paste.
+#
+# Inside a Chromium application the flag settles this on its own: with
+# autoscroll on, Blink stops pasting the primary selection on middle click,
+# because the button is doing something else now. Everywhere else on the
+# desktop middle click goes on pasting, which is the behaviour this whole
+# program exists to get away from - so the desktop's own switch for it is
+# turned off too.
+#
+# KWin has such a switch, and only for a Wayland session, where the paste is a
+# protocol the compositor either offers or does not:
+#
+#   ~/.config/kwinrc, [Wayland], EnablePrimarySelection=false
+#
+# On X11 there is nothing to switch. The primary selection is part of X itself
+# and every toolkit reaches for it on its own; no one place can say no.
+#
+# KWin reads the key once, while it starts, so what is written here is true
+# from the next login on rather than straight away.
+
+MCA_KWINRC="${MCA_XDG_CONFIG}/kwinrc"
+MCA_KWIN_GROUP="Wayland"
+MCA_KWIN_KEY="EnablePrimarySelection"
+
+# The kconfig command line tools, whichever generation this session has. They
+# are what System Settings writes kwinrc with, and worth the fork: the file has
+# a cascade behind it - /etc/xdg, the kdedefaults directory - and entries a
+# distribution can mark immutable, and an edit that reaches past all that with
+# sed writes something KDE goes on to ignore.
+MCA_KDE_TOOL=''
+MCA_KDE_TOOL_LOOKED=0
+
+_mca_kde_tool() {
+	local gen
+
+	if (( ! MCA_KDE_TOOL_LOOKED )); then
+		MCA_KDE_TOOL_LOOKED=1
+		for gen in 6 5; do
+			if mca_have "kreadconfig$gen" && mca_have "kwriteconfig$gen"; then
+				MCA_KDE_TOOL="$gen"
+				break
+			fi
+		done
+	fi
+
+	[[ -n $MCA_KDE_TOOL ]] || return 1
+	printf '%s\n' "$MCA_KDE_TOOL"
+}
+
+# mca_kde_session
+# Whether this is a KWin Wayland session.
+mca_kde_session() {
+	local desktop="${XDG_CURRENT_DESKTOP:-}"
+
+	# The watcher is a systemd service, and one started before the session
+	# imported its environment sees none of these variables. A running
+	# kwin_wayland answers both halves of the question at once, and is what
+	# such a run ends up going by.
+	if [[ -z $desktop && -z ${KDE_FULL_SESSION:-} ]]; then
+		mca_have pgrep || return 1
+		pgrep -u "$(id -u)" -x kwin_wayland > /dev/null 2>&1
+		return
+	fi
+
+	# XDG_CURRENT_DESKTOP is the one every desktop sets, and the one to go by
+	# wherever it is set; KDE_FULL_SESSION is what answers when it is not.
+	[[ -z $desktop || ${desktop^^} == *KDE* ]] || return 1
+
+	[[ ${XDG_SESSION_TYPE:-} == wayland || -n ${WAYLAND_DISPLAY:-} ]]
+}
+
+mca_kde_available() {
+	mca_kde_session && _mca_kde_tool > /dev/null
+}
+
+# mca_kde_read [file]
+# What the key says now, lowercased, empty when it is not set at all.
+mca_kde_read() {
+	local file="${1:-$MCA_KWINRC}" gen val
+	gen="$(_mca_kde_tool)" || return 1
+
+	# kreadconfig creates the file it is pointed at, and the status screen -
+	# which asks on every redraw - has no business writing anything. A file
+	# that is not there has no value in it to read anyway.
+	[[ -f $file ]] || return 0
+
+	val="$("kreadconfig$gen" --file "$file" --group "$MCA_KWIN_GROUP" \
+		--key "$MCA_KWIN_KEY" 2>/dev/null)"
+	printf '%s\n' "${val,,}"
+}
+
+# mca_kde_write [file] <value>
+# An empty value takes the key back out rather than writing nothing into it -
+# a key that is missing and a key that says nothing are not the same thing to
+# KDE, and only the first one is what an untouched kwinrc looks like.
+mca_kde_write() {
+	local file="$1" value="$2" gen
+	gen="$(_mca_kde_tool)" || return 1
+
+	if [[ -z $value ]]; then
+		"kwriteconfig$gen" --file "$file" --group "$MCA_KWIN_GROUP" \
+			--key "$MCA_KWIN_KEY" --delete 2>/dev/null
+	else
+		"kwriteconfig$gen" --file "$file" --group "$MCA_KWIN_GROUP" \
+			--key "$MCA_KWIN_KEY" "$value" 2>/dev/null
+	fi
+}
+
+# mca_kde_paste_apply
+# Turns the paste off, and remembers what the key said before so that undoing
+# puts that back rather than a guess.
+#
+# A key that already says false without the ledger knowing about it was set by
+# the user or by the distribution. That one is left alone and nothing is
+# recorded, so `disable` cannot switch a paste back on that this program never
+# switched off.
+mca_kde_paste_apply() {
+	local current previous changed=0
+
+	mca_kde_available || return 1
+	current="$(mca_kde_read)" || return 1
+
+	if mca_ledger_has "$MCA_KWINRC"; then
+		# Ours already. What goes back is the value recorded the first time
+		# round, not what reading the file now would say - that is false, and
+		# false is what is being undone.
+		previous="$(mca_ledger_detail "$MCA_KWINRC")" || previous=unset
+	elif [[ $current == false ]]; then
+		return 0
+	else
+		previous="${current:-unset}"
+	fi
+
+	if [[ $current != false ]]; then
+		mca_kde_write "$MCA_KWINRC" false || return 1
+		MCA_CHANGES=$(( MCA_CHANGES + 1 ))
+		changed=1
+	fi
+
+	mca_ledger_add kwin "$MCA_KWINRC" "$previous"
+
+	(( changed )) && mca_note "$(mca_msg "Middle click stops pasting at the next login.")"
+	return 0
+}
+
+# mca_kde_paste_revert <file> <previous value>
+mca_kde_paste_revert() {
+	local file="$1" previous="$2"
+
+	_mca_kde_tool > /dev/null || return 1
+	[[ -f $file ]] || return 1
+
+	# Only what is still recognisably ours. A key somebody has since put a
+	# value of their own into is theirs now.
+	[[ "$(mca_kde_read "$file")" == false ]] || return 1
+
+	[[ $previous == unset ]] && previous=''
+	mca_kde_write "$file" "$previous" || return 1
+
+	# Nothing was in the file but the key, which means there was no file before
+	# this program wrote one. An empty kwinrc says nothing that its absence
+	# does not say better.
+	[[ -s $file ]] || rm -f -- "$file"
+	return 0
+}

src/lib/menu.sh

@@ -0,0 +1,563 @@
+# shellcheck shell=bash
+#
+# The interactive front end.
+#
+# This is the whole configuration interface. There is a file behind it, but no
+# part of the program ever asks anyone to open it: one switch on the front
+# screen, a settings list for the categories, and a list of the applications
+# themselves for the cases where the automatic answer is not the wanted one.
+
+# Terminal mode.
+#
+# bash flips the terminal into non-canonical mode for each `read -sn1` and back
+# out again in between. That gap matters: in canonical mode DEL is the ERASE
+# character, so the line discipline eats it instead of delivering it, and a
+# backspace typed while the interface was between reads simply vanishes.
+# Holding non-canonical mode for the whole interface removes the gap.
+MCA_TERM_SAVED=''
+
+mca_ui_term_raw() {
+	mca_have stty || return 0
+	[[ -t 0 ]] || return 0
+	[[ -n $MCA_TERM_SAVED ]] && return 0
+
+	MCA_TERM_SAVED="$(stty -g 2>/dev/null)" || { MCA_TERM_SAVED=''; return 0; }
+	stty -icanon -echo min 1 time 0 2>/dev/null || true
+}
+
+mca_ui_term_restore() {
+	[[ -n $MCA_TERM_SAVED ]] || return 0
+	stty "$MCA_TERM_SAVED" 2>/dev/null || true
+	MCA_TERM_SAVED=''
+}
+
+# Runs an action with the terminal handed back to normal line mode, so anything
+# it prints - or prompts for - behaves the way a program expects.
+mca_ui_cooked() {
+	mca_ui_term_restore
+	"$@"
+	local rc=$?
+	mca_ui_term_raw
+	return $rc
+}
+
+# mca_read_key
+# One keypress, resolved to a symbolic name. Arrow keys arrive as ESC [ A, so
+# the tail of the sequence is consumed here rather than being mistaken for
+# three separate presses.
+mca_read_key() {
+	local k rest
+
+	IFS= read -rsn1 k || return 1
+
+	case "$k" in
+		$'\e')
+			if IFS= read -rsn2 -t 0.05 rest; then
+				case "$rest" in
+					'[A') printf 'up\n' ;;
+					'[B') printf 'down\n' ;;
+					'[C') printf 'right\n' ;;
+					'[D') printf 'left\n' ;;
+					*)    printf 'escape\n' ;;
+				esac
+			else
+				printf 'escape\n'
+			fi
+			;;
+		''|$'\r')      printf 'enter\n' ;;
+		$'\x7f'|$'\b') printf 'backspace\n' ;;
+		' ')           printf 'space\n' ;;
+		*)             printf '%s\n' "$k" ;;
+	esac
+}
+
+# mca_ui_read_line <initial>
+# A minimal line editor built on mca_read_key, with the result in
+# MCA_LINE_RESULT. This exists instead of bash's own `read -r` because mixing
+# line mode into a single-key interface breaks it: after one cooked-mode read
+# the following `read -sn1` stops receiving keystrokes entirely.
+MCA_LINE_RESULT=''
+
+mca_ui_read_line() {
+	local buf="${1:-}" key
+
+	MCA_LINE_RESULT=''
+	printf '%s' "$buf"
+
+	while true; do
+		key="$(mca_read_key)" || { printf '\n'; return 1; }
+
+		case "$key" in
+			enter)
+				printf '\n'
+				MCA_LINE_RESULT="$buf"
+				return 0
+				;;
+			escape)
+				printf '\n'
+				return 1
+				;;
+			backspace)
+				if [[ -n $buf ]]; then
+					buf="${buf%?}"
+					printf '\b \b'
+				fi
+				;;
+			space)
+				buf+=' '
+				printf ' '
+				;;
+			up|down|left|right) ;;
+			*)
+				[[ ${#key} -eq 1 ]] || continue
+				buf+="$key"
+				printf '%s' "$key"
+				;;
+		esac
+	done
+}
+
+mca_pause() {
+	printf '\n  %s' "$(mca_msg "Press any key to continue...")"
+	read -rsn1 _ || true
+	printf '\n'
+}
+
+# _mca_row <label> <value>
+# printf's %-28s pads by bytes, so a label containing "ü" comes out one column
+# short. ${#s} counts characters in a UTF-8 locale, so the padding is computed
+# here instead - and applied inline, because command substitution would eat the
+# trailing spaces again.
+_mca_row() {
+	local label="$1" value="$2" pad
+	pad=$(( 30 - ${#label} ))
+	(( pad < 0 )) && pad=0
+	printf '  %s%*s %s\n' "$label" "$pad" '' "$value"
+}
+
+_mca_onoff() {
+	if [[ $1 == yes ]]; then
+		printf '%s%s%s' "$MCA_C_GREEN" "$(mca_msg "ON")" "$MCA_C_RESET"
+	else
+		printf '%s%s%s' "$MCA_C_DIM" "$(mca_msg "OFF")" "$MCA_C_RESET"
+	fi
+}
+
+# ---------------------------------------------------------------------------
+# Status
+# ---------------------------------------------------------------------------
+
+# mca_ui_status
+# Shared by the `status` subcommand and the menu header. Scans, so the numbers
+# describe what is on disk right now rather than what was true at the last run.
+mca_ui_status() {
+	local last covered
+
+	mca_scan_once
+	mca_count_routes
+
+	last="$(mca_state_read last_apply '')"
+
+	_mca_row "$(mca_msg "Autoscroll")" "$(_mca_onoff "$CFG_ENABLED")"
+	printf '\n'
+
+	if [[ $CFG_ENABLED == yes ]]; then
+		covered="$MCA_N_ON"
+	else
+		covered=0
+	fi
+
+	_mca_row "$(mca_msg "Applications covered")" \
+		"$(mca_msg "%d of %d" "$covered" "$(( MCA_N_ON + MCA_N_OFF + MCA_N_UNKNOWN ))")"
+
+	if (( MCA_N_UNKNOWN )); then
+		_mca_row "$(mca_msg "Not identified")" \
+			"${MCA_C_DIM}$(mca_msg "%d - see the applications list" "$MCA_N_UNKNOWN")${MCA_C_RESET}"
+	fi
+
+	if mca_steam_installed; then
+		if mca_steam_patched; then
+			_mca_row "$(mca_msg "Steam")" "$(_mca_onoff yes)"
+		elif [[ $CFG_STEAM == yes && $CFG_ENABLED == yes ]]; then
+			_mca_row "$(mca_msg "Steam")" \
+				"${MCA_C_YELLOW}$(mca_msg "not patched yet")${MCA_C_RESET}"
+		else
+			_mca_row "$(mca_msg "Steam")" "$(_mca_onoff no)"
+		fi
+	fi
+
+	if mca_watch_available; then
+		if mca_watch_enabled; then
+			_mca_row "$(mca_msg "New applications")" "$(_mca_onoff yes)"
+		else
+			_mca_row "$(mca_msg "New applications")" "$(_mca_onoff no)"
+		fi
+	fi
+
+	# Not an ON/OFF like the rows around it: what is being reported is the state
+	# of the paste, not of a switch, and off is the state this program is after.
+	if mca_kde_available; then
+		if [[ "$(mca_kde_read)" == false ]]; then
+			_mca_row "$(mca_msg "Middle-click paste")" \
+				"${MCA_C_GREEN}$(mca_msg "off")${MCA_C_RESET}"
+		else
+			_mca_row "$(mca_msg "Middle-click paste")" \
+				"${MCA_C_DIM}$(mca_msg "on")${MCA_C_RESET}"
+		fi
+	fi
+
+	_mca_row "$(mca_msg "Last applied")" "$(mca_time_ago "$last")"
+
+	if [[ $CFG_ENABLED == yes ]]; then
+		printf '\n  %s%s%s\n' "$MCA_C_DIM" \
+			"$(mca_msg "Applications pick this up the next time they are started.")" \
+			"$MCA_C_RESET"
+	fi
+}
+
+# ---------------------------------------------------------------------------
+# Settings
+# ---------------------------------------------------------------------------
+# Format: Key|type|default|label-msgid
+# type is bool or text.
+MCA_SETTINGS=(
+	"PatchApps|bool|yes|Electron and CEF applications"
+	"PatchBrowsers|bool|yes|Chromium-based browsers"
+	"PatchFlatpak|bool|yes|Flatpak applications"
+	"PatchSnap|bool|yes|Snap applications"
+	"PatchAutostart|bool|yes|Programs that start themselves at login"
+	"PatchSteam|bool|yes|Steam"
+	"PatchSpotify|bool|yes|Spotify"
+	"DisablePaste|bool|yes|Turn off KDE's middle-click paste"
+	"WatchNewApps|bool|yes|Apply to newly installed applications"
+	"ExtraFlags|text||Additional Chromium arguments"
+)
+
+_mca_is_true() {
+	case "${1,,}" in
+		yes|y|true|1|on|enabled) return 0 ;;
+		*) return 1 ;;
+	esac
+}
+
+MCA_SETTING_SHOWN=''
+MCA_LBL_ON=''
+MCA_LBL_OFF=''
+MCA_LBL_NONE=''
+
+_mca_setting_display() {
+	local type="$1" value="$2"
+
+	case "$type" in
+		bool)
+			if _mca_is_true "$value"; then
+				MCA_SETTING_SHOWN="${MCA_C_GREEN}${MCA_LBL_ON}${MCA_C_RESET}"
+			else
+				MCA_SETTING_SHOWN="${MCA_C_DIM}${MCA_LBL_OFF}${MCA_C_RESET}"
+			fi
+			;;
+		text)
+			if [[ -n $value ]]; then
+				MCA_SETTING_SHOWN="$value"
+			else
+				MCA_SETTING_SHOWN="${MCA_C_DIM}${MCA_LBL_NONE}${MCA_C_RESET}"
+			fi
+			;;
+		*) MCA_SETTING_SHOWN="$value" ;;
+	esac
+}
+
+# mca_ui_settings
+# A cursor list rather than a numbered menu. The frame is assembled in memory
+# and written once, and everything constant is resolved before the loop:
+# drawing the naive way costs a command substitution per label per frame, which
+# is slow enough that arrow keys feel like the console is reloading.
+#
+# Returns 0 when something was changed, so the caller knows to re-apply.
+mca_ui_settings() {
+	local count=${#MCA_SETTINGS[@]}
+	local -a names=() types=() defaults=() labels=() values=()
+	local spec name type default label locale i key frame row pad dirty=1 cursor=0
+	local touched=0
+
+	locale="$(mca_ui_locale)"
+	mca_msg_into "$locale" "ON";     MCA_LBL_ON="$MCA_MSG_RESULT"
+	mca_msg_into "$locale" "OFF";    MCA_LBL_OFF="$MCA_MSG_RESULT"
+	mca_msg_into "$locale" "(none)"; MCA_LBL_NONE="$MCA_MSG_RESULT"
+
+	for spec in "${MCA_SETTINGS[@]}"; do
+		IFS='|' read -r name type default label <<< "$spec"
+		names+=("$name"); types+=("$type"); defaults+=("$default")
+		mca_msg_into "$locale" "$label"
+		labels+=("$MCA_MSG_RESULT")
+	done
+
+	local title hint
+	mca_msg_into "$locale" "Settings"; title="$MCA_MSG_RESULT"
+	mca_msg_into "$locale" "Up/Down select - Space or Right changes - q goes back"
+	hint="$MCA_MSG_RESULT"
+
+	local clearseq
+	clearseq="$(clear 2>/dev/null)" || clearseq=$'\033[H\033[2J'
+
+	while true; do
+		if (( dirty )); then
+			for i in "${!names[@]}"; do
+				_mca_config_lookup "${names[i]}" "${defaults[i]}"
+				values[i]="$MCA_CONFIG_VALUE"
+			done
+			dirty=0
+		fi
+
+		frame="$clearseq"$'\n'"${MCA_C_BOLD}${MCA_C_BLUE}  ${title}${MCA_C_RESET}"$'\n\n'
+
+		local marker selected="${MCA_C_BLUE}▸${MCA_C_RESET} "
+		for i in "${!names[@]}"; do
+			_mca_setting_display "${types[i]}" "${values[i]}"
+			pad=$(( 46 - ${#labels[i]} ))
+			(( pad < 0 )) && pad=0
+			if (( i == cursor )); then marker="$selected"; else marker='  '; fi
+			printf -v row '  %s%s%*s %s' \
+				"$marker" "${labels[i]}" "$pad" '' "$MCA_SETTING_SHOWN"
+			frame+="$row"$'\n'
+		done
+
+		frame+=$'\n'"  ${MCA_C_DIM}${hint}${MCA_C_RESET}"$'\n'
+		printf '%s' "$frame"
+
+		key="$(mca_read_key)" || return "$(( ! touched ))"
+
+		type="${types[cursor]}"
+		name="${names[cursor]}"
+
+		case "$key" in
+			up|k)   cursor=$(( (cursor - 1 + count) % count )) ;;
+			down|j) cursor=$(( (cursor + 1) % count )) ;;
+			space|enter|right|l|left|h)
+				if [[ $type == text ]]; then
+					[[ $key == left || $key == h ]] && continue
+					mca_ui_edit_text "$name" "${values[cursor]}" && touched=1
+				else
+					if _mca_is_true "${values[cursor]}"; then
+						mca_config_set "$name" no
+					else
+						mca_config_set "$name" yes
+					fi || { mca_bad "$(mca_msg "Could not save the setting.")"; mca_pause; }
+					touched=1
+				fi
+				dirty=1
+				;;
+			q|Q|escape) return "$(( ! touched ))" ;;
+			*) ;;
+		esac
+	done
+}
+
+# mca_ui_edit_text <key> <current>
+mca_ui_edit_text() {
+	local name="$1" current="$2"
+
+	printf '\n  %s\n' "$(mca_msg "Arguments separated by spaces, empty for none:")"
+	printf '  > '
+
+	if mca_ui_read_line "$current"; then
+		mca_config_set "$name" "$MCA_LINE_RESULT" \
+			|| { mca_bad "$(mca_msg "Could not save the setting.")"; mca_pause; }
+		return 0
+	fi
+	return 1
+}
+
+# ---------------------------------------------------------------------------
+# Applications
+# ---------------------------------------------------------------------------
+
+# mca_ui_apps
+# Every application that was found, what will happen to it, and a key to
+# change that. This is where an AppImage that could not be identified gets
+# turned on, and where a single application gets left out without having to
+# switch off its whole category.
+#
+# Returns 0 when something was changed.
+mca_ui_apps() {
+	local count key frame row pad i cursor=0 dirty=1 touched=0 locale
+	local -a labels=() states=()
+
+	locale="$(mca_ui_locale)"
+
+	local title hint legend warn
+	mca_msg_into "$locale" "Applications"; title="$MCA_MSG_RESULT"
+	mca_msg_into "$locale" "Up/Down select - Space turns one on or off - q goes back"
+	hint="$MCA_MSG_RESULT"
+	mca_msg_into "$locale" "Anything not identified is left alone until it is turned on here."
+	legend="$MCA_MSG_RESULT"
+	mca_msg_into "$locale" "Autoscroll is off - this is what would be covered."
+	warn="$MCA_MSG_RESULT"
+
+	# The per-row labels are resolved once, here. Looking them up inside the
+	# drawing loop is a fork per row per keypress, and that is enough to make
+	# the arrow keys feel like the screen is reloading.
+	local l_off l_cannot l_on l_steam l_flagfile l_launcher
+	mca_msg_into "$locale" "off";         l_off="$MCA_MSG_RESULT"
+	mca_msg_into "$locale" "cannot tell"; l_cannot="$MCA_MSG_RESULT"
+	mca_msg_into "$locale" "on";          l_on="$MCA_MSG_RESULT"
+	mca_msg_into "$locale" "Steam";       l_steam="$MCA_MSG_RESULT"
+	mca_msg_into "$locale" "flag file";   l_flagfile="$MCA_MSG_RESULT"
+	mca_msg_into "$locale" "launcher";    l_launcher="$MCA_MSG_RESULT"
+
+	local s_off="${MCA_C_DIM}${l_off}${MCA_C_RESET}"
+	local s_cannot="${MCA_C_DIM}${l_cannot}${MCA_C_RESET}"
+	local s_on="${MCA_C_GREEN}${l_on}${MCA_C_RESET}"
+	local s_steam="${s_on} ${MCA_C_DIM}(${l_steam})${MCA_C_RESET}"
+	local s_flags="${s_on} ${MCA_C_DIM}(${l_flagfile})${MCA_C_RESET}"
+	local s_desktop="${s_on} ${MCA_C_DIM}(${l_launcher})${MCA_C_RESET}"
+
+	local clearseq
+	clearseq="$(clear 2>/dev/null)" || clearseq=$'\033[H\033[2J'
+
+	printf '%s\n  %s\n' "$clearseq" "$(mca_msg "Looking at the installed applications...")"
+	mca_config_load
+	mca_scan_once
+	count=${#MCA_IDS[@]}
+
+	if (( count == 0 )); then
+		printf '\n  %s\n' "$(mca_msg "No Chromium-based applications found.")"
+		mca_pause
+		return 1
+	fi
+
+	while true; do
+		if (( dirty )); then
+			mca_config_load
+			mca_count_routes
+			labels=(); states=()
+			for i in "${!MCA_IDS[@]}"; do
+				labels+=("${MCA_NAMES[i]}")
+				states+=("${MCA_ROUTES[i]}")
+			done
+			dirty=0
+		fi
+
+		frame="$clearseq"$'\n'"${MCA_C_BOLD}${MCA_C_BLUE}  ${title}${MCA_C_RESET}"$'\n\n'
+
+		local marker selected="${MCA_C_BLUE}▸${MCA_C_RESET} " shown
+		for i in "${!labels[@]}"; do
+			case "${states[i]}" in
+				off)     shown="$s_off" ;;
+				unknown) shown="$s_cannot" ;;
+				steam)   shown="$s_steam" ;;
+				flags)   shown="$s_flags" ;;
+				*)       shown="$s_desktop" ;;
+			esac
+			pad=$(( 34 - ${#labels[i]} ))
+			(( pad < 0 )) && pad=0
+			if (( i == cursor )); then marker="$selected"; else marker='  '; fi
+			printf -v row '  %s%s%*s %s' "$marker" "${labels[i]}" "$pad" '' "$shown"
+			frame+="$row"$'\n'
+		done
+
+		frame+=$'\n'
+		# Without this the list reads as a list of what is switched on, which
+		# it is not while the whole thing is off.
+		if [[ $CFG_ENABLED != yes ]]; then
+			frame+="  ${MCA_C_YELLOW}${warn}${MCA_C_RESET}"$'\n'
+		fi
+		frame+="  ${MCA_C_DIM}${legend}${MCA_C_RESET}"$'\n'
+		frame+="  ${MCA_C_DIM}${hint}${MCA_C_RESET}"$'\n'
+		printf '%s' "$frame"
+
+		key="$(mca_read_key)" || return "$(( ! touched ))"
+
+		case "$key" in
+			up|k)   cursor=$(( (cursor - 1 + count) % count )) ;;
+			down|j) cursor=$(( (cursor + 1) % count )) ;;
+			space|enter|right|left|l|h)
+				case "${states[cursor]}" in
+					off|unknown)
+						mca_config_list_del Skip "${MCA_IDS[cursor]}"
+						mca_config_list_add Include "${MCA_IDS[cursor]}"
+						;;
+					*)
+						mca_config_list_del Include "${MCA_IDS[cursor]}"
+						mca_config_list_add Skip "${MCA_IDS[cursor]}"
+						;;
+				esac
+				touched=1
+				dirty=1
+				;;
+			q|Q|escape) return "$(( ! touched ))" ;;
+			*) ;;
+		esac
+	done
+}
+
+# ---------------------------------------------------------------------------
+# The menu
+# ---------------------------------------------------------------------------
+
+mca_ui_menu() {
+	local choice
+
+	mca_ui_term_raw
+	trap 'mca_ui_term_restore' EXIT INT TERM
+
+	while true; do
+		mca_config_load
+
+		clear 2>/dev/null || true
+		mca_head "  $MCA_PRETTY"
+		mca_ui_status
+		printf '\n'
+		printf '  [1] %s\n' "$(mca_msg "Turn autoscroll on or off")"
+		printf '  [2] %s\n' "$(mca_msg "Re-apply everything")"
+		printf '  [3] %s\n' "$(mca_msg "Applications")"
+		printf '  [4] %s\n' "$(mca_msg "Settings")"
+		printf '  [q] %s\n' "$(mca_msg "Quit")"
+		printf '\n  > '
+
+		choice="$(mca_read_key)" || {
+			printf '\n'; mca_ui_term_restore; trap - EXIT INT TERM; return 0
+		}
+		case "$choice" in
+			enter|space|up|down|left|right|escape) choice='' ;;
+		esac
+		printf '%s\n' "$choice"
+
+		case "$choice" in
+			1)
+				MCA_UI_NEEDS_ACK=''
+				if [[ $CFG_ENABLED == yes ]]; then
+					mca_ui_cooked mca_do_disable
+				else
+					mca_ui_cooked mca_do_enable
+				fi
+				[[ -n $MCA_UI_NEEDS_ACK ]] && mca_pause
+				;;
+			# Not a plain apply: with the watcher running there is never
+			# anything left for one to do, and a menu entry that answers
+			# "already done" every time is not an action. This is the repair -
+			# everything is taken back and written again from scratch, which is
+			# what fixes an application that drifted, a flag file somebody
+			# edited, or Steam after it restored its own script.
+			2)
+				mca_ui_cooked mca_do_apply --rebuild
+				mca_pause
+				;;
+			3)
+				if mca_ui_apps; then
+					[[ $CFG_ENABLED == yes ]] && mca_ui_cooked mca_do_apply --rebuild
+				fi
+				;;
+			4)
+				if mca_ui_settings; then
+					[[ $CFG_ENABLED == yes ]] && mca_ui_cooked mca_do_apply --rebuild
+				fi
+				;;
+			q|Q) mca_ui_term_restore; trap - EXIT INT TERM; return 0 ;;
+			# Anything else - Enter, arrow keys, stray characters - just
+			# redraws. Escape is deliberately not a quit key, so a mistyped
+			# arrow key cannot close the menu.
+			*) ;;
+		esac
+	done
+}

src/lib/patch.sh

@@ -0,0 +1,659 @@
+# shellcheck shell=bash
+#
+# Putting the flag where the application will read it, and taking it back out.
+#
+# There are two ways in, and the order matters:
+#
+#   1. A flag file. Where the distribution wraps Electron and Chromium in a
+#      launcher script that reads extra arguments from
+#      $XDG_CONFIG_HOME/<name>-flags.conf - Arch and its derivatives do, and it
+#      is the convention their packages follow - this is the good one: it is
+#      the supported way to pass arguments, it survives package upgrades
+#      untouched, and it applies however the program is started, including from
+#      a terminal.
+#
+#      Nothing is assumed about which distribution this is. The launcher itself
+#      is read, and the route is taken only for a launcher that really does
+#      name such a file. Elsewhere - Debian, Ubuntu, Fedora, openSUSE, where
+#      the equivalent file lives under /etc and is the system's to write -
+#      there is no flag file to use and route 2 answers for everything.
+#
+#   2. A desktop entry. For applications that ship their own binary with no
+#      wrapper, and for everything a Flatpak or a snap contains, there is
+#      nowhere else to put an argument, so a copy of the entry with the flag
+#      appended goes into ~/.local/share/applications, where it shadows the
+#      system one.
+#
+# Nothing outside $HOME is ever written to.
+
+MCA_MARK_BEGIN='# >>> middleclick-autoscroll'
+MCA_MARK_END='# <<< middleclick-autoscroll'
+
+# ---------------------------------------------------------------------------
+# Feature lists
+# ---------------------------------------------------------------------------
+# Both --enable-features and --enable-blink-features take a comma separated
+# list, and Chromium keeps the last one it is given and drops the rest. A
+# second one of the same kind would therefore silently switch off whatever the
+# first one turned on, so an option that is already there is extended instead.
+
+# _mca_list_merge <list> <wanted>
+# The two lists as one, in the order they came and without repeating anything.
+_mca_list_merge() {
+	local out="$1" item
+	for item in ${2//,/ }; do
+		[[ ",$out," == *",$item,"* ]] && continue
+		out="${out:+$out,}$item"
+	done
+	printf '%s' "$out"
+}
+
+# _mca_list_strip <list> <unwanted>
+# The list without any of the named entries.
+_mca_list_strip() {
+	local out='' item
+	for item in ${1//,/ }; do
+		[[ ",$2," == *",$item,"* ]] && continue
+		out="${out:+$out,}$item"
+	done
+	printf '%s' "$out"
+}
+
+# The two options, as a regular expression branch, for the places that have to
+# recognise either of them.
+MCA_FEATURE_OPTS='--enable-blink-features|--enable-features'
+
+# ---------------------------------------------------------------------------
+# Command lines
+# ---------------------------------------------------------------------------
+
+# _mca_exec_insert_at <exec line>
+# Where an argument has to go: after the program and its own arguments, but
+# before the first field code (%U and friends) or Flatpak's @@ markers, which
+# are placeholders the launcher expands rather than arguments.
+_mca_exec_insert_at() {
+	local rest="$1" tok idx=0
+
+	while [[ -n $rest ]]; do
+		while [[ $rest == ' '* ]]; do rest="${rest# }"; idx=$(( idx + 1 )); done
+		[[ -n $rest ]] || break
+		tok="${rest%% *}"
+		case "$tok" in
+			%[a-zA-Z]|@@|@@u) printf '%s\n' "$idx"; return 0 ;;
+		esac
+		rest="${rest:${#tok}}"
+		idx=$(( idx + ${#tok} ))
+	done
+
+	printf '%s\n' "$(( ${#1} ))"
+}
+
+# _mca_exec_after_program <exec line>
+# The position just after the program name, for arguments that a program only
+# accepts before its positional ones.
+_mca_exec_after_program() {
+	local rest="$1" idx=0 tok
+
+	while [[ $rest == ' '* ]]; do rest="${rest# }"; idx=$(( idx + 1 )); done
+	tok="${rest%% *}"
+	printf '%s\n' "$(( idx + ${#tok} ))"
+}
+
+# mca_exec_inject <exec line> [flags] [position: before-fields|after-program]
+# The same line with the given flags added, defaulting to the configured ones.
+# Prints nothing and returns 1 when there was nothing to change, so callers can
+# tell a real edit from a no-op without diffing.
+#
+# A feature list that is already on the line is extended rather than repeated.
+# See _mca_list_merge.
+mca_exec_inject() {
+	local line="$1" flagstr="${2:-}" where="${3:-before-fields}"
+	local flag opt value existing merged re at changed=0
+	local -a flags
+
+	[[ -n $flagstr ]] || flagstr="$(mca_flags)"
+	read -r -a flags <<< "$flagstr"
+
+	for flag in "${flags[@]}"; do
+		case "$flag" in
+			--enable-blink-features=*|--enable-features=*)
+				opt="${flag%%=*}"
+				value="${flag#*=}"
+				re="(^|[[:space:]])$opt=([^[:space:]]*)"
+				if [[ $line =~ $re ]]; then
+					existing="${BASH_REMATCH[2]}"
+					merged="$(_mca_list_merge "$existing" "$value")"
+					[[ $merged == "$existing" ]] && continue
+					line="${line/$opt=$existing/$opt=$merged}"
+					changed=1
+					continue
+				fi
+				;;
+		esac
+
+		[[ " $line " == *" $flag "* ]] && continue
+
+		if [[ $where == after-program ]]; then
+			at="$(_mca_exec_after_program "$line")"
+			line="${line:0:$at} $flag${line:$at}"
+		else
+			at="$(_mca_exec_insert_at "$line")"
+			if (( at >= ${#line} )); then
+				line="${line% } $flag"
+			else
+				line="${line:0:$at}$flag ${line:$at}"
+			fi
+		fi
+		changed=1
+	done
+
+	(( changed )) || return 1
+	printf '%s\n' "$line"
+}
+
+# ---------------------------------------------------------------------------
+# Flag files
+# ---------------------------------------------------------------------------
+
+# mca_flags_apply <program> [kind]
+# Writes the flags into the file the program's launcher reads. Returns 0 when
+# the program has such a file (whether or not anything needed changing), 1 when
+# it has none and the desktop entry route has to be used instead.
+mca_flags_apply() {
+	local prog="$1" kind="${2:-app}" name target='' existing_target=''
+	local -a candidates=()
+
+	mapfile -t candidates < <(mca_flags_candidates "$prog" | awk '!seen[$0]++')
+	(( ${#candidates[@]} )) || return 1
+
+	# A wrapper that offers several files reads the first one that exists and
+	# ignores the rest, so an existing file is always the right one to edit.
+	for name in "${candidates[@]}"; do
+		if [[ -f "$MCA_XDG_CONFIG/$name" ]]; then
+			existing_target="$name"
+			_mca_flags_write "$MCA_XDG_CONFIG/$name" "$kind"
+		fi
+	done
+	[[ -n $existing_target ]] && return 0
+
+	# None exists yet. The last candidate is the wrapper's own fallback - the
+	# generic electron-flags.conf rather than electron43-flags.conf - so
+	# creating that one also covers every other application using the same
+	# shared Electron.
+	target="${candidates[-1]}"
+	_mca_flags_write "$MCA_XDG_CONFIG/$target" "$kind"
+	return 0
+}
+
+# _mca_flags_write <file> [kind]
+# Adds the flags as a marked block, or merges into a feature list that is
+# already in the file.
+_mca_flags_write() {
+	local file="$1" kind="${2:-app}"
+	local content='' line flag opt want existing merged=0 block=''
+	local -a flags
+	local -A merged_opts=()
+	local created=0
+
+	read -r -a flags <<< "$(mca_flags "$kind")"
+
+	[[ -f $file ]] || created=1
+	if (( ! created )); then
+		content="$(< "$file")"
+		# Already ours: the block is rewritten below, so drop the old one first.
+		if [[ $content == *"$MCA_MARK_BEGIN"* ]]; then
+			content="$(_mca_flags_drop_block "$file")"
+		fi
+	fi
+
+	# Merge into a feature list the user (or a distribution) put there, rather
+	# than write a second line of the same option further down.
+	if [[ $content == *--enable-* ]]; then
+		local out=''
+		while IFS= read -r line; do
+			if [[ $line =~ ^[[:space:]]*($MCA_FEATURE_OPTS)=([^[:space:]]*)[[:space:]]*$ ]]; then
+				opt="${BASH_REMATCH[1]}"
+				existing="${BASH_REMATCH[2]}"
+				want=''
+				for flag in "${flags[@]}"; do
+					[[ $flag == "$opt="* ]] && want="${flag#*=}"
+				done
+				if [[ -n $want ]]; then
+					line="$opt=$(_mca_list_merge "$existing" "$want")"
+					merged_opts["$opt"]=1
+					merged=1
+				fi
+			fi
+			out+="$line"$'\n'
+		done <<< "$content"
+		content="${out%$'\n'}"
+	fi
+
+	for flag in "${flags[@]}"; do
+		[[ -n ${merged_opts["${flag%%=*}"]:-} ]] && continue
+		block+="$flag"$'\n'
+	done
+
+	if [[ -n $block ]]; then
+		content="${content:+$content$'\n'}$MCA_MARK_BEGIN"$'\n'"$block$MCA_MARK_END"
+	fi
+
+	if mca_write_if_changed "$file" "$content"$'\n'; then
+		MCA_CHANGES=$(( MCA_CHANGES + 1 ))
+	fi
+
+	if (( created )); then
+		mca_ledger_add flags "$file" created
+	elif (( merged )) && [[ -z $block ]]; then
+		mca_ledger_add flags "$file" merged
+	elif (( merged )); then
+		mca_ledger_add flags "$file" merged+block
+	else
+		mca_ledger_add flags "$file" block
+	fi
+
+	return 0
+}
+
+_mca_flags_drop_block() {
+	awk -v b="$MCA_MARK_BEGIN" -v e="$MCA_MARK_END" '
+		$0 == b { skip = 1; next }
+		$0 == e { skip = 0; next }
+		!skip
+	' "$1" 2>/dev/null
+}
+
+# mca_flags_revert <file> <detail>
+mca_flags_revert() {
+	local file="$1" detail="$2" content line out='' opt existing new
+
+	[[ -f $file ]] || return 0
+
+	case "$detail" in
+		created)
+			# Only remove the file if nothing but our block ended up in it;
+			# anything else means the user started using it in the meantime.
+			content="$(_mca_flags_drop_block "$file")"
+			if [[ -z ${content//[[:space:]]/} ]]; then
+				rm -f -- "$file"
+				return 0
+			fi
+			;;
+	esac
+
+	content="$(_mca_flags_drop_block "$file")"
+
+	if [[ $detail == merged* ]]; then
+		while IFS= read -r line; do
+			if [[ $line =~ ^[[:space:]]*($MCA_FEATURE_OPTS)=([^[:space:]]*)[[:space:]]*$ ]]; then
+				opt="${BASH_REMATCH[1]}"
+				existing="${BASH_REMATCH[2]}"
+				# Either name, whichever version of this program put it there.
+				new="$(_mca_list_strip "$existing" "$MCA_BROWSER_FEATURES")"
+				[[ -z $new ]] && continue
+				line="$opt=$new"
+			fi
+			out+="$line"$'\n'
+		done <<< "$content"
+		content="${out%$'\n'}"
+	fi
+
+	if [[ -z ${content//[[:space:]]/} ]]; then
+		rm -f -- "$file"
+	else
+		printf '%s\n' "$content" > "$file"
+	fi
+	return 0
+}
+
+# ---------------------------------------------------------------------------
+# Desktop entries
+# ---------------------------------------------------------------------------
+
+# A generated entry and an entry that was edited in place look similar and must
+# never be confused: the first one is ours to delete, the second one is the
+# user's file with one line changed and has to be restored from its backup. They
+# carry different markers so that the scan, the "already done" checks and the
+# undo can all tell them apart.
+MCA_MARK_SHADOW='X-MCA-Generated'
+MCA_MARK_INPLACE='X-MCA-Patched'
+
+# _mca_desktop_transform <file> <marker> [flags] [position]
+# The whole file with every Exec line rewritten - the main one and the one in
+# each Desktop Action, because those are the right-click menu entries and a
+# user who starts Steam from "Library" expects the same behaviour there.
+_mca_desktop_transform() {
+	local file="$1" marker="$2" flags="${3:-}" where="${4:-before-fields}"
+	local line rest new marked=0
+
+	while IFS= read -r line || [[ -n $line ]]; do
+		case "$line" in
+			Exec=*)
+				rest="${line#Exec=}"
+				new="$(mca_exec_inject "$rest" "$flags" "$where")" && line="Exec=$new"
+				;;
+			# A D-Bus activated entry is started through its service file and
+			# the Exec line is never used, so the flag would go nowhere.
+			DBusActivatable=true)
+				line='DBusActivatable=false'
+				;;
+			# A marker from an older version; the current one is written below.
+			X-MCA-*)
+				continue
+				;;
+		esac
+
+		printf '%s\n' "$line"
+
+		if (( ! marked )) && [[ $line =~ ^[[:space:]]*\[Desktop\ Entry\][[:space:]]*$ ]]; then
+			printf '%s=%s\n' "$marker" "$MCA_VERSION"
+			marked=1
+		fi
+	done < "$file"
+}
+
+# mca_desktop_apply <id> <source entry> [flags] [position]
+# Puts a patched copy in ~/.local/share/applications, or patches the entry in
+# place when it already lives there.
+mca_desktop_apply() {
+	local id="$1" src="$2" flags="${3:-}" where="${4:-before-fields}"
+	local target="$MCA_APPDIR/$id.desktop" content backup
+
+	if [[ "$src" == "$target" ]]; then
+		# The user's own entry - an AppImage, a web app shortcut, something
+		# installed by hand. There is nowhere to shadow it from, so it is
+		# edited directly and the original is kept.
+		grep -q "^$MCA_MARK_INPLACE=" "$src" 2>/dev/null && return 0
+
+		content="$(_mca_desktop_transform "$src" "$MCA_MARK_INPLACE" "$flags" "$where")"
+		[[ -n $content ]] || return 1
+		[[ "$content" == "$(< "$src")" ]] && return 0
+
+		backup="$(mca_backup "$src")" || return 1
+		if mca_write_if_changed "$src" "$content"$'\n'; then
+			MCA_CHANGES=$(( MCA_CHANGES + 1 ))
+		fi
+		mca_ledger_add inplace "$src" "$backup"
+		return 0
+	fi
+
+	content="$(_mca_desktop_transform "$src" "$MCA_MARK_SHADOW" "$flags" "$where")"
+	[[ -n $content ]] || return 1
+
+	mkdir -p "$MCA_APPDIR" 2>/dev/null || return 1
+
+	# Something is already shadowing this entry. Unless it is a shadow of ours,
+	# it is the user's own file - possibly one we edited in place earlier - and
+	# overwriting it here would lose it.
+	if [[ -e $target ]] && ! grep -q "^$MCA_MARK_SHADOW=" "$target" 2>/dev/null; then
+		return 1
+	fi
+
+	if mca_write_if_changed "$target" "$content"$'\n'; then
+		MCA_CHANGES=$(( MCA_CHANGES + 1 ))
+	fi
+	mca_ledger_add shadow "$target" "$src"
+	return 0
+}
+
+# ---------------------------------------------------------------------------
+# Entries outside the search path
+# ---------------------------------------------------------------------------
+# Two directories hold desktop entries that no part of the XDG search path
+# looks at, so nothing the scan does can reach them:
+#
+#   ~/.config/autostart, where applications that start themselves at login
+#   write their own entry, pointing straight at their binary. Those bypass the
+#   entry in the menu completely, which is why Discord launched at login used
+#   to behave differently from Discord launched from the menu.
+#
+#   The desktop folder, where a shortcut somebody dragged out of the menu -
+#   or asked Steam for - lives and nowhere else.
+#
+# Neither can be shadowed from anywhere, so both are edited where they stand,
+# with the original kept.
+
+# _mca_entry_patch_inplace <file> <gate: autostart|apps>
+# One desktop entry that lives outside the XDG search path, edited where it is
+# because there is nowhere to shadow it from.
+#
+# What decides whether an application here is in scope differs by where the
+# entry came from, which is what the gate says: an autostart entry follows the
+# autostart setting, a shortcut follows the same rules as the application it is
+# a shortcut to.
+_mca_entry_patch_inplace() {
+	local file="$1" gate="$2"
+	local id prog packaging=native content backup kind copy
+
+	# Already ours, and normally that is the end of it: what is in there is what
+	# this version put there. Not so for a file the ledger has no record of -
+	# nothing would ever look at that one again, neither the undo a change of
+	# flags goes through nor this, which leaves a marked file alone, and it would
+	# keep an answer from an older version for good. The copy taken before the
+	# edit is named after the path and is still there, so the file goes back to
+	# what it was and is written again below.
+	if grep -q "^$MCA_MARK_INPLACE=" "$file" 2>/dev/null; then
+		mca_ledger_has "$file" && return 0
+		copy="$MCA_BACKUPDIR/$(mca_backup_name "$file")"
+		[[ -f $copy ]] || return 0
+		cp -p -- "$copy" "$file" 2>/dev/null || return 0
+	fi
+
+	_mca_desktop_read "$file"
+	[[ -n $DE_EXEC ]] || return 0
+	[[ $DE_HIDDEN == true ]] && return 0
+
+	mca_exec_program "$DE_EXEC" || return 0
+	prog="$MCA_PROG"
+
+	# A Flatpak or a snap entry names the wrapper rather than the application.
+	# The scan resolves those into an id; outside the scan the same has to
+	# happen here, or every Flatpak looks like the flatpak program itself.
+	if [[ ${prog##*/} == flatpak ]]; then
+		mca_exec_flatpak_id "$DE_EXEC" || return 0
+		prog="flatpak:$MCA_PROG"
+		packaging=flatpak
+	elif mca_snap_name "$prog"; then
+		prog="snap:$MCA_PROG"
+		packaging=snap
+	fi
+
+	# An entry that starts Steam is left where it is. Steam takes nothing
+	# from a command line that would help, and what it does take belongs to
+	# the web helper script in its own installation.
+	mca_prog_is_steam "$prog" && return 0
+
+	case "$packaging" in
+		flatpak) mca_flatpak_is_chromium "${prog#flatpak:}" || return 0 ;;
+		snap)    mca_snap_is_chromium "${prog#snap:}" || return 0 ;;
+		*)       mca_is_chromium "$prog" || return 0 ;;
+	esac
+
+	mca_desktop_is_browser && kind=browser || kind=app
+
+	if [[ $gate == autostart ]]; then
+		[[ $CFG_AUTOSTART == yes ]] || return 0
+	else
+		id="${file##*/}"; id="${id%.desktop}"
+		mca_kind_wanted "$kind" "$id" "$packaging" || return 0
+	fi
+
+	content="$(_mca_desktop_transform "$file" "$MCA_MARK_INPLACE" \
+		"$(mca_flags "$kind")")"
+
+	[[ -n $content ]] || return 0
+	[[ "$content" == "$(< "$file")" ]] && return 0
+
+	backup="$(mca_backup "$file")" || return 0
+	if mca_write_if_changed "$file" "$content"$'\n'; then
+		MCA_CHANGES=$(( MCA_CHANGES + 1 ))
+	fi
+	mca_ledger_add inplace "$file" "$backup"
+}
+
+mca_autostart_apply() {
+	local dir="$MCA_XDG_CONFIG/autostart" file
+
+	[[ -d $dir ]] || return 0
+
+	for file in "$dir"/*.desktop; do
+		[[ -f $file ]] || continue
+		_mca_entry_patch_inplace "$file" autostart
+	done
+}
+
+mca_shortcuts_apply() {
+	local dir file
+	dir="$(mca_desktop_folder)"
+
+	[[ -d $dir ]] || return 0
+
+	for file in "$dir"/*.desktop; do
+		[[ -f $file ]] || continue
+		_mca_entry_patch_inplace "$file" apps
+	done
+}
+
+# ---------------------------------------------------------------------------
+# Spotify
+# ---------------------------------------------------------------------------
+# The official client is CEF rather than Electron and, when installed through
+# spotify-launcher, is started by a program that builds its own command line.
+# That launcher has a configuration file with a slot for exactly this.
+
+mca_spotify_apply() {
+	local file="$MCA_XDG_CONFIG/spotify-launcher.conf" content line out='' backup
+	local found_section=0 found_args=0
+
+	mca_have spotify-launcher || return 0
+
+	if [[ -f $file ]]; then
+		content="$(< "$file")"
+		while IFS= read -r line; do
+			if [[ $line =~ ^[[:space:]]*\[spotify\][[:space:]]*$ ]]; then
+				found_section=1
+			elif [[ $line =~ ^[[:space:]]*extra_arguments[[:space:]]*=[[:space:]]*\[(.*)\][[:space:]]*$ ]]; then
+				local args="${BASH_REMATCH[1]}"
+				found_args=1
+				if [[ $args != *"$MCA_FEATURE"* ]]; then
+					line="extra_arguments = [${args:+$args, }\"$MCA_FLAG\"]"
+				fi
+			fi
+			out+="$line"$'\n'
+		done <<< "$content"
+		content="${out%$'\n'}"
+	fi
+
+	if (( ! found_args )); then
+		(( found_section )) || content="${content:+$content$'\n'}[spotify]"
+		content="${content:+$content$'\n'}extra_arguments = [\"$MCA_FLAG\"]"
+	fi
+
+	[[ -f $file ]] && backup="$(mca_backup "$file")"
+
+	if mca_write_if_changed "$file" "$content"$'\n'; then
+		MCA_CHANGES=$(( MCA_CHANGES + 1 ))
+	fi
+	mca_ledger_add inplace "$file" "${backup:-}"
+	return 0
+}
+
+# ---------------------------------------------------------------------------
+# Leftovers
+# ---------------------------------------------------------------------------
+
+# mca_prune_orphans
+# Forgets changes there is no longer anything to undo.
+#
+# Uninstalling something deletes its entry from /usr/share/applications, but the
+# copy shadowing it is in the user's home and pacman knows nothing about it. It
+# would sit in the menu forever, offering to start a program that is no longer
+# installed - and the watcher would not notice, because a plain apply only ever
+# looks at what is there now. A file that was edited where it stood and has
+# since been deleted is the same problem from the other side: its record would
+# have `disable` put the file back.
+mca_prune_orphans() {
+	local kind path source line
+	local -a lines=()
+
+	[[ -f $MCA_LEDGER ]] || return 0
+	mapfile -t lines < "$MCA_LEDGER"
+
+	for line in "${lines[@]}"; do
+		IFS=$'\t' read -r kind path source <<< "$line"
+
+		# An entry that was edited where it stood and has since been deleted -
+		# a game shortcut dragged to the wastebasket, an autostart entry the
+		# application removed. There is nothing left to put back, and keeping
+		# the record would have `disable` recreate a file the user threw away.
+		if [[ $kind == inplace && ! -e $path ]]; then
+			[[ -n $source ]] && rm -f -- "$MCA_BACKUPDIR/$source"
+			mca_ledger_forget "$path"
+			continue
+		fi
+
+		[[ $kind == shadow && -n $source ]] || continue
+		[[ -e $source ]] && continue
+
+		# Only ever remove something still recognisably ours.
+		if [[ -f $path ]] && grep -q "^$MCA_MARK_SHADOW=" "$path" 2>/dev/null; then
+			rm -f -- "$path"
+			MCA_CHANGES=$(( MCA_CHANGES + 1 ))
+		fi
+		mca_ledger_forget "$path"
+	done
+	return 0
+}
+
+# ---------------------------------------------------------------------------
+# Undo
+# ---------------------------------------------------------------------------
+
+mca_revert_all() {
+	local kind path detail
+
+	[[ -f $MCA_LEDGER ]] || return 0
+
+	# Backwards, so a file that was recorded twice ends up at its oldest state.
+	while IFS=$'\t' read -r kind path detail; do
+		[[ -n $path ]] || continue
+		case "$kind" in
+			shadow)
+				# Only remove what is still recognisably ours.
+				if [[ -f $path ]] && grep -q "^$MCA_MARK_SHADOW=" "$path" 2>/dev/null; then
+					rm -f -- "$path"
+					MCA_CHANGES=$(( MCA_CHANGES + 1 ))
+				fi
+				;;
+			inplace)
+				if [[ -n $detail && -f "$MCA_BACKUPDIR/$detail" ]]; then
+					if [[ -e $path ]] || [[ -d "$(dirname -- "$path")" ]]; then
+						cp -p -- "$MCA_BACKUPDIR/$detail" "$path" 2>/dev/null \
+							&& MCA_CHANGES=$(( MCA_CHANGES + 1 ))
+					fi
+					rm -f -- "$MCA_BACKUPDIR/$detail"
+				elif [[ -f $path ]]; then
+					# No backup: the file did not exist before we wrote it.
+					rm -f -- "$path"
+					MCA_CHANGES=$(( MCA_CHANGES + 1 ))
+				fi
+				;;
+			flags)
+				mca_flags_revert "$path" "$detail" \
+					&& MCA_CHANGES=$(( MCA_CHANGES + 1 ))
+				;;
+			steam)
+				mca_steam_revert "$path" "$detail" \
+					&& MCA_CHANGES=$(( MCA_CHANGES + 1 ))
+				;;
+			kwin)
+				mca_kde_paste_revert "$path" "$detail" \
+					&& MCA_CHANGES=$(( MCA_CHANGES + 1 ))
+				;;
+		esac
+	done < <(tac "$MCA_LEDGER" 2>/dev/null)
+
+	rm -f -- "$MCA_LEDGER"
+	rmdir "$MCA_BACKUPDIR" 2>/dev/null || true
+	return 0
+}

src/lib/steam.sh

@@ -0,0 +1,287 @@
+# shellcheck shell=bash
+#
+# Steam.
+#
+# Steam's interface is CEF, so the feature is there - but Steam builds the
+# command line for its web helper itself and offers no way to add to it. The
+# only place to get an argument in is the shell script that starts the helper,
+# which lives inside Steam's own installation:
+#
+#   ~/.local/share/Steam/ubuntu12_64/steamwebhelper_sniper_wrap.sh
+#
+# Steam compares the installed files against its manifest at every start - by
+# size and timestamp rather than by content - and restores whatever differs.
+# So the patch is written to look untouched: the bytes the flag costs are taken
+# back out of the script's comments and the timestamp is put back afterwards,
+# which leaves a file that is byte-for-byte the size Steam recorded and as old
+# as Steam left it. A client that verifies its files finds nothing to repair
+# and the flag survives however Steam was started - from the menu, from a game
+# shortcut, from a launcher like Heroic, from a terminal.
+#
+# A patch that changes the length is not an option, and no switch covers for
+# one. Steam checks its files at a start it was given arguments for, but also
+# at the shutdown it runs itself - and that one has no -noverifyfiles on its
+# command line, whatever the session was started with. What a single wrong
+# length costs is the whole client package downloaded, extracted and installed
+# again, and a client that quits at the end of it instead of coming up. So the
+# flag either fits in the space the comments give back, or it is not written at
+# all: no autoscroll in the interface is a smaller thing than a client that
+# reinstalls itself.
+#
+# The file comes back on every client update, and the watcher re-applies the
+# patch when that happens.
+
+# Every place a Steam installation is known to live, resolved and de-duplicated
+# because ~/.steam/steam is normally a symlink into ~/.local/share.
+#
+# Which of these is the real one depends on how Steam was installed: Valve's
+# own package and the Arch one use ~/.local/share/Steam, Debian's puts it in
+# ~/.steam/debian-installation, and the Flatpak and the snap each keep it
+# inside the private tree their sandbox gives them.
+mca_steam_roots() {
+	local candidates=(
+		"$MCA_XDG_DATA/Steam"
+		"$HOME/.steam/steam"
+		"$HOME/.steam/root"
+		"$HOME/.steam/debian-installation"
+		"$HOME/.var/app/com.valvesoftware.Steam/.local/share/Steam"
+		"$HOME/.var/app/com.valvesoftware.Steam/data/Steam"
+		"$HOME/snap/steam/common/.local/share/Steam"
+	)
+	local dir real
+	local -A seen=()
+
+	for dir in "${candidates[@]}"; do
+		[[ -d $dir ]] || continue
+		real="$(readlink -f -- "$dir" 2>/dev/null)" || continue
+		[[ -n ${seen[$real]+set} ]] && continue
+		seen[$real]=1
+		printf '%s\n' "$real"
+	done
+}
+
+# The script to patch inside a Steam installation. Newer clients start the
+# helper through a wrapper inside the container runtime; older ones exec it
+# from steamwebhelper.sh directly, and that one forwards its arguments too.
+mca_steam_script() {
+	local root="$1" f
+	for f in \
+		"$root/ubuntu12_64/steamwebhelper_sniper_wrap.sh" \
+		"$root/ubuntu12_64/steamwebhelper.sh"
+	do
+		[[ -f $f && -w $f ]] && { printf '%s\n' "$f"; return 0; }
+	done
+	return 1
+}
+
+mca_steam_installed() {
+	local root
+	while IFS= read -r root; do
+		mca_steam_script "$root" > /dev/null && return 0
+	done < <(mca_steam_roots)
+	return 1
+}
+
+# mca_steam_script_patched <script>
+mca_steam_script_patched() {
+	grep -q -- "$MCA_FEATURE" "$1" 2>/dev/null
+}
+
+mca_steam_patched() {
+	local root script
+	while IFS= read -r root; do
+		script="$(mca_steam_script "$root")" || continue
+		mca_steam_script_patched "$script" && return 0
+	done < <(mca_steam_roots)
+	return 1
+}
+
+# _mca_steam_exec_line <script>
+# The line number of the command that starts the web helper: the last
+# uncommented line that both names steamwebhelper and forwards "$@". Both the
+# current layout (exec ./steamwebhelper "$@" inside the container wrapper) and
+# the older one (steamwebhelper.sh handing the arguments to the runtime entry
+# point) end in exactly that.
+_mca_steam_exec_line() {
+	awk '
+		/^[[:space:]]*#/ { next }
+		/steamwebhelper/ && /"\$@"/ { n = NR }
+		END { if (n) print n }
+	' "$1" 2>/dev/null
+}
+
+# _mca_steam_build <script> <flags>
+# The patched script on stdout: the flags appended to the line that starts the
+# web helper, and the same number of bytes taken back out of the script's
+# comments, so that the file Steam finds is the length Steam wrote down.
+# Everything else - setting up the container runtime, deciding whether the
+# sandbox can be used - is left alone.
+#
+# Comments are eaten from the bottom up, so the header that says what the
+# script is for is the last thing to lose anything, and the '#' itself always
+# stays: a line that loses it stops being a comment and starts being a command.
+# Fails when the comments are too short to pay for the flags.
+_mca_steam_build() {
+	local script="$1" flags="$2" lineno need
+
+	lineno="$(_mca_steam_exec_line "$script")"
+	[[ -n $lineno ]] || return 1
+
+	need="$(printf '%s' " $flags" | wc -c)"
+	need="${need//[^0-9]/}"
+
+	# LC_ALL=C so awk counts bytes: a comment with an accent in it is shorter
+	# in characters than it is on disk, and it is the disk that Steam measures.
+	LC_ALL=C awk -v n="$lineno" -v f=" $flags" -v need="$need" '
+		{ lines[NR] = (NR == n ? $0 f : $0) }
+		END {
+			for (i = NR; i >= 2 && need > 0; i--) {
+				if (i == n) continue
+				p = index(lines[i], "#")
+				if (p == 0) continue
+				# Only a line that is nothing but a comment; a trailing one
+				# sits behind a command that has to stay intact.
+				if (substr(lines[i], 1, p - 1) ~ /[^ \t]/) continue
+				can = length(lines[i]) - p
+				if (can <= 0) continue
+				if (can > need) can = need
+				lines[i] = substr(lines[i], 1, length(lines[i]) - can)
+				need -= can
+			}
+			if (need > 0) exit 1
+			for (i = 1; i <= NR; i++) print lines[i]
+		}
+	' "$script"
+}
+
+# _mca_steam_same_size <script> <content>
+# Whether writing that content leaves the file at the size it has now. Measured
+# rather than worked out: a script without a final newline gains one on the way
+# through awk, and one byte is all it takes for Steam to notice.
+_mca_steam_same_size() {
+	local script="$1" content="$2"
+	(( $(wc -c < "$script") == $(printf '%s\n' "$content" | wc -c) ))
+}
+
+# _mca_steam_refresh_backup <script>
+# A client update brings a new version of the script, and the copy kept from
+# before it is no longer what putting it back means. Only ever done while the
+# script is unpatched, so the copy that replaces it is Steam's own.
+_mca_steam_refresh_backup() {
+	local script="$1" name
+	name="$(mca_backup_name "$script")"
+
+	[[ -e "$MCA_BACKUPDIR/$name" ]] || return 0
+	cmp -s -- "$script" "$MCA_BACKUPDIR/$name" && return 0
+	cp -p -- "$script" "$MCA_BACKUPDIR/$name" 2>/dev/null || true
+}
+
+# _mca_steam_settle <script> <flags>
+# The script is already patched. Whether that is a patch Steam can live with is
+# a question of length: an earlier version of this program appended the flag
+# where the comments could not pay for it, which leaves the script longer than
+# the file Steam wrote down - and a client that checks its files reinstalls
+# itself over that, then quits instead of starting.
+#
+# Rebuilt from the untouched original kept when the script was first patched,
+# never from the patched file, the flag either fits this time or the original
+# goes back and Steam is left with a client it recognises.
+_mca_steam_settle() {
+	local script="$1" flags="$2" name copy out
+
+	name="$(mca_backup_name "$script")"
+	copy="$MCA_BACKUPDIR/$name"
+
+	# Nothing to compare against, so nothing can be said about the length.
+	[[ -f $copy ]] || return 0
+
+	# Already the length Steam expects: the patch is a good one.
+	(( $(wc -c < "$script") == $(wc -c < "$copy") )) && return 0
+
+	if out="$(_mca_steam_build "$copy" "$flags")" && _mca_steam_same_size "$copy" "$out"; then
+		if mca_write_if_changed "$script" "$out"$'\n'; then
+			MCA_CHANGES=$(( MCA_CHANGES + 1 ))
+		fi
+		chmod +x -- "$script" 2>/dev/null || true
+		touch -r "$copy" -- "$script" 2>/dev/null || true
+		mca_ledger_add steam "$script" "$name"
+		return 0
+	fi
+
+	mca_steam_revert "$script" "$name"
+	mca_ledger_forget "$script"
+	mca_note "$(mca_msg "Steam's interface cannot be given the flag without leaving a file Steam would reinstall; the change has been taken back.")"
+	return 0
+}
+
+# mca_steam_apply
+# Puts the flags into every Steam installation that has the script, and only
+# where that can be done without changing how long the file is. Returns 1 when
+# there is no Steam to patch at all.
+mca_steam_apply() {
+	local root script backup flags found=0 out
+
+	flags="$(mca_flags)"
+
+	while IFS= read -r root; do
+		script="$(mca_steam_script "$root")" || continue
+		found=1
+
+		if mca_steam_script_patched "$script"; then
+			_mca_steam_settle "$script" "$flags"
+			continue
+		fi
+
+		_mca_steam_refresh_backup "$script"
+
+		# Either the comments can pay for the flag or nothing is written.
+		# A longer file is one Steam reinstalls itself over; a client update
+		# that changed how the helper is started leaves no line to patch at
+		# all. Both end here, and this script is what starts Steam's entire
+		# interface, so leaving it alone is the only safe answer to either.
+		if ! { out="$(_mca_steam_build "$script" "$flags")" \
+			&& _mca_steam_same_size "$script" "$out"; }
+		then
+			mca_note "$(mca_msg "Steam starts its interface in a way this version cannot change without Steam noticing; leaving it alone.")"
+			continue
+		fi
+
+		backup="$(mca_backup "$script")" || continue
+		if mca_write_if_changed "$script" "$out"$'\n'; then
+			MCA_CHANGES=$(( MCA_CHANGES + 1 ))
+		fi
+		chmod +x -- "$script" 2>/dev/null || true
+
+		# Steam looks at when the file was last written as well as at how big
+		# it is, and the copy taken before the edit still carries the original
+		# timestamp. Putting it back costs nothing and removes the other half
+		# of what the client would notice.
+		touch -r "$MCA_BACKUPDIR/$backup" -- "$script" 2>/dev/null || true
+
+		mca_ledger_add steam "$script" "$backup"
+	done < <(mca_steam_roots)
+
+	(( found ))
+}
+
+# mca_steam_revert <script> <backup name>
+mca_steam_revert() {
+	local script="$1" backup="$2"
+
+	if [[ -n $backup && -f "$MCA_BACKUPDIR/$backup" ]]; then
+		if [[ -e $script ]]; then
+			cp -p -- "$MCA_BACKUPDIR/$backup" "$script" 2>/dev/null || true
+			chmod +x -- "$script" 2>/dev/null || true
+		fi
+		rm -f -- "$MCA_BACKUPDIR/$backup"
+		return 0
+	fi
+
+	# No backup to fall back on - take the flags back out of the exec line.
+	[[ -f $script ]] || return 1
+	local tmp
+	tmp="$(mktemp "${script}.XXXXXX")" || return 1
+	sed "s| $MCA_FLAG||g" "$script" > "$tmp" && mv -f "$tmp" "$script" || { rm -f "$tmp"; return 1; }
+	chmod +x -- "$script" 2>/dev/null || true
+	return 0
+}

src/middleclick-autoscroll

@@ -0,0 +1,208 @@
+#!/usr/bin/env bash
+#
+# middleclick-autoscroll - middle-click autoscroll for Chromium-based
+# applications on Linux
+#
+# Blink has had Windows-style autoscroll for years, behind a runtime flag that
+# is not turned on for Linux because middle click is taken by primary-selection
+# paste there. Turning it on is a matter of one command line argument - the
+# work is finding every application that needs it, putting the argument
+# somewhere it survives an update, and doing the same for the two programs that
+# do not take arguments at all.
+#
+# Copyright (C) 2026 Felitendo
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+set -uo pipefail
+
+MCA_LIBDIR="${MCA_LIBDIR:-@LIBDIR@}"
+
+for _mod in common config detect patch steam kde apply menu; do
+	# shellcheck source=/dev/null
+	if ! source "$MCA_LIBDIR/$_mod.sh"; then
+		printf 'middleclick-autoscroll: cannot load %s/%s.sh\n' "$MCA_LIBDIR" "$_mod" >&2
+		exit 14
+	fi
+done
+unset _mod
+
+# Nothing here writes outside $HOME, so running it as root would patch root's
+# own applications and leave the actual user without any.
+if [[ $EUID -eq 0 && -z ${MCA_ALLOW_ROOT:-} ]]; then
+	printf 'middleclick-autoscroll: run this as your own user, not as root.\n' >&2
+	exit 2
+fi
+
+# ---------------------------------------------------------------------------
+# Commands
+# ---------------------------------------------------------------------------
+
+mca_do_enable() {
+	mca_config_set Enabled yes || {
+		mca_bad "$(mca_msg "Could not save the setting.")"
+		return 1
+	}
+	mca_config_load
+
+	mca_apply
+
+	if [[ $CFG_WATCH == yes ]]; then
+		if mca_watch_available; then
+			mca_watch_enable || mca_note "$(mca_msg "Could not start the watcher for newly installed applications.")"
+		else
+			mca_note "$(mca_msg "No systemd user session - newly installed applications will not be picked up on their own.")"
+		fi
+	fi
+
+	mca_ok "$(mca_msg "Autoscroll is on for %d applications." "$MCA_N_ON")"
+
+	mca_note "$(mca_msg "Applications that are already running pick this up when they are restarted.")"
+}
+
+mca_do_disable() {
+	mca_config_set Enabled no || {
+		mca_bad "$(mca_msg "Could not save the setting.")"
+		return 1
+	}
+
+	mca_revert
+	mca_watch_disable
+
+	mca_ok "$(mca_msg "Autoscroll is off and everything that was changed has been put back.")"
+}
+
+mca_do_apply() {
+	local rebuild=0 arg
+
+	for arg in "$@"; do
+		case "$arg" in
+			--rebuild) rebuild=1 ;;
+			--quiet)   MCA_QUIET=1 ;;
+		esac
+	done
+
+	mca_config_load
+
+	if [[ $CFG_ENABLED != yes ]]; then
+		# Called by the watcher while switched off: there is nothing to do, and
+		# nothing to complain about either.
+		[[ -n $MCA_QUIET ]] && return 0
+		mca_note "$(mca_msg "Autoscroll is off. Turn it on first.")"
+		return 1
+	fi
+
+	# Start from a clean slate. Needed after a settings change, which can take
+	# an application out of scope as well as bring one in and where only a full
+	# undo can tell the difference, and it is what makes the repair a repair:
+	# whatever drifted is written again rather than left because it is "already
+	# applied".
+	#
+	# The watcher never does this. Rewriting files that are already correct
+	# would change their timestamps, and it is watching those directories.
+	if (( rebuild )); then
+		mca_revert
+	fi
+
+	mca_apply
+
+	if (( rebuild )); then
+		mca_ok "$(mca_msg "Applied again to %d applications." "$MCA_N_ON")"
+		mca_say "  $(mca_msg "Applications that are already running pick this up when they are restarted.")"
+	elif (( MCA_CHANGES )); then
+		mca_ok "$(mca_msg "Applied to %d applications." "$MCA_N_ON")"
+		mca_say "  $(mca_msg "Applications that are already running pick this up when they are restarted.")"
+	else
+		mca_ok "$(mca_msg "Already applied to %d applications." "$MCA_N_ON")"
+	fi
+
+	if [[ $CFG_WATCH == yes ]] && mca_watch_available; then
+		if mca_watch_enabled; then
+			mca_watch_refresh
+		else
+			mca_watch_enable || true
+		fi
+	elif [[ $CFG_WATCH != yes ]] && mca_watch_enabled; then
+		mca_watch_disable
+	fi
+}
+
+mca_do_status() {
+	mca_config_load
+	mca_head "  $MCA_PRETTY"
+	mca_ui_status
+	printf '\n'
+}
+
+mca_do_list() {
+	local i route label pad
+
+	mca_config_load
+	mca_scan_once
+	mca_count_routes
+
+	if (( ${#MCA_IDS[@]} == 0 )); then
+		mca_note "$(mca_msg "No Chromium-based applications found.")"
+		return 0
+	fi
+
+	mca_head "  $(mca_msg "Applications")"
+
+	for i in "${!MCA_IDS[@]}"; do
+		route="${MCA_ROUTES[i]}"
+		label="${MCA_NAMES[i]}"
+		pad=$(( 34 - ${#label} ))
+		(( pad < 0 )) && pad=0
+		printf '  %s%*s %s\n' "$label" "$pad" '' "$(mca_route_label "$route")"
+	done
+	printf '\n'
+}
+
+mca_do_help() {
+	cat <<- EOF
+	$MCA_PRETTY $MCA_VERSION
+
+	$(mca_msg "Usage: middleclick-autoscroll [command]")
+
+	$(mca_msg "Commands:")
+	  enable              $(mca_msg "Turn autoscroll on")
+	  disable             $(mca_msg "Turn it off and put everything back")
+	  apply               $(mca_msg "Apply to anything installed since the last run")
+	  apply --rebuild     $(mca_msg "Take everything back and apply it again")
+	  status              $(mca_msg "Show what is covered")
+	  list                $(mca_msg "List every application that was found")
+	  -h, --help          $(mca_msg "Show this help")
+	  -V, --version       $(mca_msg "Show the version")
+
+	$(mca_msg "Without a command an interactive menu is shown.")
+	EOF
+}
+
+# ---------------------------------------------------------------------------
+# Dispatch
+# ---------------------------------------------------------------------------
+
+main() {
+	local cmd="${1:-}"
+	[[ $# -gt 0 ]] && shift
+
+	case "$cmd" in
+		enable)  mca_do_enable "$@" ;;
+		disable) mca_do_disable "$@" ;;
+		apply|refresh) mca_do_apply "$@" ;;
+		status)  mca_do_status "$@" ;;
+		list)    mca_do_list "$@" ;;
+
+		-h|--help|help) mca_do_help ;;
+		-V|--version)   printf '%s %s\n' "$MCA_NAME" "$MCA_VERSION" ;;
+
+		'') mca_ui_menu ;;
+		*)
+			mca_bad "$(mca_msg "Unknown command: %s" "$cmd")"
+			printf '\n'
+			mca_do_help
+			exit 1
+			;;
+	esac
+}
+
+main "$@"