modrinth-enhanced, modrinth-enhanced-bin: preload vblank shim for the full refresh rate on nvidia

modrinth-enhanced-bin/.SRCINFO

@@ -1,7 +1,7 @@
 pkgbase = modrinth-enhanced-bin
 	pkgdesc = Modrinth App without ads or telemetry, with offline and Ely.by accounts and Linux fixes (upstream binary)
 	pkgver = 0.21.2
-	pkgrel = 1
+	pkgrel = 2
 	url = https://github.com/Felitendo/Modrinth-Enhanced
 	arch = x86_64
 	license = GPL-3.0-only
@@ -12,6 +12,7 @@ pkgbase = modrinth-enhanced-bin
 	depends = glibc
 	depends = gtk3
 	depends = hicolor-icon-theme
+	depends = libdrm
 	depends = libgcc
 	depends = libsoup3
 	depends = webkit2gtk-4.1
@@ -28,6 +29,10 @@ pkgbase = modrinth-enhanced-bin
 	options = !strip
 	options = !debug
 	source = modrinth-enhanced-bin-0.21.2.deb::https://github.com/Felitendo/Modrinth-Enhanced/releases/download/v0.21.2/Modrinth.Enhanced_0.21.2_amd64.deb
+	source = vblank-shim.c
+	source = modrinth-enhanced.sh
 	sha256sums = 32ed32575050b4ac1a990b54a894e82c17860a48d5a228ce0d1ce7fc2c9d5d6f
+	sha256sums = 0190921b8ff2fb1deec3209cba71c01541ca1f013e3ba41680f1636e185fd455
+	sha256sums = b24872f82645c52ee4804599cd678d138876fb193c754403fa9c5cf92bd745b9
 
 pkgname = modrinth-enhanced-bin

modrinth-enhanced-bin/PKGBUILD

@@ -4,13 +4,13 @@
 
 pkgname=modrinth-enhanced-bin
 pkgver=0.21.2
-pkgrel=1
+pkgrel=2
 pkgdesc="Modrinth App without ads or telemetry, with offline and Ely.by accounts and Linux fixes (upstream binary)"
 arch=('x86_64')
 url="https://github.com/Felitendo/Modrinth-Enhanced"
 license=('GPL-3.0-only')
 depends=('cairo' 'dbus' 'gdk-pixbuf2' 'glib2' 'glibc' 'gtk3' 'hicolor-icon-theme'
-         'libgcc' 'libsoup3' 'webkit2gtk-4.1'
+         'libdrm' 'libgcc' 'libsoup3' 'webkit2gtk-4.1'
          # loaded by Minecraft, not by the launcher
          'libgl' 'libpulse' 'libx11' 'libxcursor' 'libxext' 'libxxf86vm')
 optdepends=('xorg-xrandr: for older Minecraft versions')
@@ -21,12 +21,30 @@ options=('!strip' '!debug')
 # v0.21.2-2, which pkgver spells 0.21.2.r2; see pkg.sh.
 _tag="v0.21.2"
 _asset="Modrinth.Enhanced_0.21.2_amd64.deb"
-source=("${pkgname}-${pkgver}.deb::https://github.com/Felitendo/Modrinth-Enhanced/releases/download/${_tag}/${_asset}")
+# With the NVIDIA driver WebKitGTK paces the app with a 60 fps timer whatever
+# the monitor's refresh rate. vblank-shim.c, preloaded by modrinth-enhanced.sh,
+# paces it at the monitor's rate instead and keeps the app on X11, the only
+# place that works; it is not part of upstream's release.
+source=("${pkgname}-${pkgver}.deb::https://github.com/Felitendo/Modrinth-Enhanced/releases/download/${_tag}/${_asset}"
+        "vblank-shim.c"
+        "modrinth-enhanced.sh")
 noextract=("${pkgname}-${pkgver}.deb")
-sha256sums=('32ed32575050b4ac1a990b54a894e82c17860a48d5a228ce0d1ce7fc2c9d5d6f')
+sha256sums=('32ed32575050b4ac1a990b54a894e82c17860a48d5a228ce0d1ce7fc2c9d5d6f' '0190921b8ff2fb1deec3209cba71c01541ca1f013e3ba41680f1636e185fd455' 'b24872f82645c52ee4804599cd678d138876fb193c754403fa9c5cf92bd745b9')
+
+build() {
+  # GLib for its headers only: the shim looks GTK and GLib up at run time
+  gcc $CPPFLAGS $CFLAGS $LDFLAGS -shared -fPIC -o libwebkit-vblank-shim.so vblank-shim.c \
+    $(pkg-config --cflags glib-2.0) $(pkg-config --cflags --libs libdrm)
+}
 
 package() {
   bsdtar -xOf "$srcdir/${pkgname}-${pkgver}.deb" 'data.tar.*' \
     | bsdtar -xpf - -C "$pkgdir" usr
+
+  # the binary moves behind the script that preloads the shim
+  install -d "$pkgdir/usr/lib/modrinth-enhanced"
+  mv "$pkgdir/usr/bin/ModrinthEnhanced" "$pkgdir/usr/lib/modrinth-enhanced/"
+  install -Dm755 libwebkit-vblank-shim.so -t "$pkgdir/usr/lib/modrinth-enhanced/"
+  install -Dm755 modrinth-enhanced.sh "$pkgdir/usr/bin/ModrinthEnhanced"
   ln -s ModrinthEnhanced "$pkgdir/usr/bin/modrinth-enhanced"
 }

modrinth-enhanced-bin/modrinth-enhanced.sh

@@ -0,0 +1,9 @@
+#!/bin/sh
+# Starts Modrinth Enhanced with the vblank shim preloaded (see vblank-shim.c).
+# With the NVIDIA driver the shim only lifts the frame rate under X11, so it is
+# asked to keep GTK on X11 there. MODRINTH_VBLANK_SHIM=0 starts the app without.
+if [ "${MODRINTH_VBLANK_SHIM:-1}" != 0 ]; then
+  [ -d /sys/module/nvidia_drm ] && export VBLANK_SHIM_GDK_BACKEND=x11
+  export LD_PRELOAD="/usr/lib/modrinth-enhanced/libwebkit-vblank-shim.so${LD_PRELOAD:+:$LD_PRELOAD}"
+fi
+exec /usr/lib/modrinth-enhanced/ModrinthEnhanced "$@"

modrinth-enhanced-bin/pkg.sh

@@ -2,9 +2,10 @@
 # the Modrinth App (Tauri) with a series of patches applied: no ads, no
 # telemetry, offline and Ely.by accounts, Linux fixes.
 #
-# Upstream publishes a bundled .deb per release, so there is no build step
+# Upstream publishes a bundled .deb per release, so the app is not built here:
-# here: on a new version only pkgver, the tag, the asset name and the checksum
+# on a new version only pkgver, the tag, the asset name and the checksums are
-# are refreshed and the PKGBUILD repackages the deb directly.
+# refreshed and the PKGBUILD repackages the deb directly. The only thing built
+# is vblank-shim.c, which ships with this package (see the PKGBUILD).
 #
 # Releases are tagged after the Modrinth App release they are built on
 # (v0.21.2). When the patches change without a new Modrinth App release, the
@@ -18,6 +19,9 @@
 
 UPSTREAM_REPO="Felitendo/Modrinth-Enhanced"
 
+# Installed in CI before the makepkg test build, for the shim's headers.
+BUILD_DEPS=(glib2 libdrm)
+
 latest_version() {
   gh api "repos/$UPSTREAM_REPO/releases/latest" --jq '.tag_name' | sed 's/^v//; s/-/.r/'
 }
@@ -25,7 +29,11 @@ latest_version() {
 # refresh_checksums <version> <pkgbuild-path>
 refresh_checksums() {
   local ver="$1" pkgbuild="$2"
-  local tag="v${ver/.r/-}" asset sha
+  local tag="v${ver/.r/-}" dir asset sha sha_shim sha_script
+
+  dir="$(dirname "$pkgbuild")"
+  sha_shim="$(sha256sum "$dir/vblank-shim.c" | cut -d' ' -f1)"
+  sha_script="$(sha256sum "$dir/modrinth-enhanced.sh" | cut -d' ' -f1)"
 
   asset="$(gh api "repos/$UPSTREAM_REPO/releases/tags/$tag" \
     --jq '.assets[].name | select(endswith("_amd64.deb"))')"
@@ -40,6 +48,6 @@ refresh_checksums() {
   sed -i \
     -e "s|^_tag=.*|_tag=\"$tag\"|" \
     -e "s|^_asset=.*|_asset=\"$asset\"|" \
-    -e "s|^sha256sums=.*|sha256sums=('$sha')|" \
+    -e "s|^sha256sums=.*|sha256sums=('$sha' '$sha_shim' '$sha_script')|" \
     "$pkgbuild"
 }

modrinth-enhanced-bin/vblank-shim.c

@@ -0,0 +1,437 @@
+// LD_PRELOAD shim that lets Modrinth Enhanced (WebKitGTK 4.1 on GTK3) draw at
+// the monitor's refresh rate with the NVIDIA driver instead of 60 Hz.
+//
+// Three things hold it at 60 Hz there:
+//  1. WebKitGTK looks for the DRM CRTC of the monitor a window is on by
+//     physical size, and the NVIDIA DRM connector reports slightly different
+//     millimetres than GDK does, so no CRTC is found.
+//  2. The NVIDIA DRM driver does not implement DRM_IOCTL_WAIT_VBLANK, so even a
+//     found CRTC cannot be waited on. WebKit then paces with a 60 fps timer.
+//  3. GTK3 paces its own paints from the refresh interval the display server
+//     reports, and assumes 60 Hz without one. KWin reports none to it, on X11
+//     (no _NET_WM_FRAME_TIMINGS for XWayland clients) and on Wayland alike.
+//
+// This shim:
+//  1. corrects the connector size to what GDK reports for the same monitor,
+//     found by output name on X11 ("DP-1") or EDID model name on Wayland;
+//  2. emulates blocking vblank waits at the CRTC's refresh rate when the
+//     driver refuses them;
+//  3. fills in the monitor refresh interval on GTK3 frame timings that were
+//     left without one.
+//
+// Each step only stands in for what is missing, so with drivers that report
+// all of it the shim changes nothing.
+//
+// The frame rate only comes through on X11: on Wayland something in GTK3 or
+// WebKit still asks for 60 frames a second. VBLANK_SHIM_GDK_BACKEND=x11 keeps
+// GTK on X11 without setting GDK_BACKEND, which every program the app starts
+// would inherit. A GDK_BACKEND the user set still wins.
+//
+// Build: gcc -shared -fPIC -O2 -o libwebkit-vblank-shim.so vblank-shim.c $(pkg-config --cflags glib-2.0) $(pkg-config --cflags --libs libdrm)
+// Debug: VBLANK_SHIM_DEBUG=1
+// Knobs: VBLANK_SHIM_RATE_MULTIPLIER (vblank emulation), VBLANK_SHIM_REFRESH_HZ
+//        (GTK frame timings, default: fastest monitor), VBLANK_SHIM_FRAME_CLOCK=0
+//        (leave GTK frame timings alone)
+
+#define _GNU_SOURCE
+#include <ctype.h>
+#include <dlfcn.h>
+#include <errno.h>
+#include <glib-object.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <xf86drm.h>
+#include <xf86drmMode.h>
+
+typedef struct _GdkDisplay GdkDisplay;
+typedef struct _GdkMonitor GdkMonitor;
+typedef struct _GdkWindow GdkWindow;
+typedef struct _GdkFrameClock GdkFrameClock;
+typedef struct _GdkFrameTimings GdkFrameTimings;
+
+static int debug_enabled(void) {
+    static int value = -1;
+    if (value < 0) value = getenv("VBLANK_SHIM_DEBUG") != NULL;
+    return value;
+}
+
+#define debug(...) do { if (debug_enabled()) fprintf(stderr, "vblank-shim: " __VA_ARGS__); } while (0)
+
+// --- 0. Window system -------------------------------------------------------
+
+static char gdk_backend[16];
+
+// Read on load, while nothing else runs, and taken out of the environment.
+__attribute__((constructor))
+static void take_gdk_backend(void) {
+    const char *backend = getenv("VBLANK_SHIM_GDK_BACKEND");
+    if (!backend) return;
+    snprintf(gdk_backend, sizeof gdk_backend, "%s", backend);
+    unsetenv("VBLANK_SHIM_GDK_BACKEND");
+}
+
+static void select_gdk_backend(void) {
+    if (!gdk_backend[0] || getenv("GDK_BACKEND")) return;
+    void (*set_allowed_backends)(const char *) = dlsym(RTLD_DEFAULT, "gdk_set_allowed_backends");
+    if (set_allowed_backends) {
+        set_allowed_backends(gdk_backend);
+        debug("GDK limited to %s\n", gdk_backend);
+    }
+    gdk_backend[0] = '\0';
+}
+
+int gtk_init_check(int *argc, char ***argv) {
+    static int (*real)(int *, char ***);
+    if (!real) real = dlsym(RTLD_NEXT, "gtk_init_check");
+    select_gdk_backend();
+    return real(argc, argv);
+}
+
+void gtk_init(int *argc, char ***argv) {
+    static void (*real)(int *, char ***);
+    if (!real) real = dlsym(RTLD_NEXT, "gtk_init");
+    select_gdk_backend();
+    real(argc, argv);
+}
+
+// WebKit waits for vblank and GTK paints in the process the shim is preloaded
+// into. Its children - WebKit's helper processes, and Minecraft started from
+// the launcher - have no use for it, so it leaves LD_PRELOAD on load and keeps
+// whatever else is in there.
+__attribute__((constructor))
+static void leave_ld_preload(void) {
+    const char *preload = getenv("LD_PRELOAD");
+    Dl_info info;
+    if (!preload || !dladdr((void *)leave_ld_preload, &info) || !info.dli_fname) return;
+    const char *self = strrchr(info.dli_fname, '/');
+    self = self ? self + 1 : info.dli_fname;
+
+    char *entries = strdup(preload), *kept = calloc(1, strlen(preload) + 1);
+    if (entries && kept) {
+        char *save = NULL;
+        for (char *entry = strtok_r(entries, ": ", &save); entry; entry = strtok_r(NULL, ": ", &save)) {
+            const char *name = strrchr(entry, '/');
+            if (strcmp(name ? name + 1 : entry, self) == 0) continue;
+            if (*kept) strcat(kept, ":");
+            strcat(kept, entry);
+        }
+        if (*kept) setenv("LD_PRELOAD", kept, 1);
+        else unsetenv("LD_PRELOAD");
+    }
+    free(entries);
+    free(kept);
+}
+
+// GTK and GLib are looked up at run time rather than linked, so the shim loads
+// into processes without them (such as the shell script that starts the
+// AppImage) and still finds them when they are loaded later with dlopen.
+static struct {
+    GdkDisplay *(*display_get_default)(void);
+    int (*display_get_n_monitors)(GdkDisplay *);
+    GdkMonitor *(*display_get_monitor)(GdkDisplay *, int);
+    const char *(*monitor_get_model)(GdkMonitor *);
+    int (*monitor_get_width_mm)(GdkMonitor *);
+    int (*monitor_get_height_mm)(GdkMonitor *);
+    int (*monitor_get_refresh_rate)(GdkMonitor *);
+    GType (*frame_clock_get_type)(void);
+    GdkFrameTimings *(*frame_clock_get_current_timings)(GdkFrameClock *);
+    gint64 (*frame_timings_get_refresh_interval)(GdkFrameTimings *);
+    gpointer (*type_class_ref)(GType);
+    guint (*signal_lookup)(const gchar *, GType);
+    gulong (*signal_add_emission_hook)(guint, GQuark, GSignalEmissionHook, gpointer, GDestroyNotify);
+    gpointer (*value_get_object)(const GValue *);
+} gtk;
+
+static int gtk_resolved(void) {
+    if (gtk.value_get_object) return 1;
+    #define RESOLVE(field, name) if (!(gtk.field = dlsym(RTLD_DEFAULT, name))) return 0
+    RESOLVE(display_get_default, "gdk_display_get_default");
+    RESOLVE(display_get_n_monitors, "gdk_display_get_n_monitors");
+    RESOLVE(display_get_monitor, "gdk_display_get_monitor");
+    RESOLVE(monitor_get_model, "gdk_monitor_get_model");
+    RESOLVE(monitor_get_width_mm, "gdk_monitor_get_width_mm");
+    RESOLVE(monitor_get_height_mm, "gdk_monitor_get_height_mm");
+    RESOLVE(monitor_get_refresh_rate, "gdk_monitor_get_refresh_rate");
+    RESOLVE(frame_clock_get_type, "gdk_frame_clock_get_type");
+    RESOLVE(frame_clock_get_current_timings, "gdk_frame_clock_get_current_timings");
+    RESOLVE(frame_timings_get_refresh_interval, "gdk_frame_timings_get_refresh_interval");
+    RESOLVE(type_class_ref, "g_type_class_ref");
+    RESOLVE(signal_lookup, "g_signal_lookup");
+    RESOLVE(signal_add_emission_hook, "g_signal_add_emission_hook");
+    RESOLVE(value_get_object, "g_value_get_object");
+    #undef RESOLVE
+    return 1;
+}
+
+// --- 1. Connector size ------------------------------------------------------
+
+static const char *connector_prefix(uint32_t type) {
+    switch (type) {
+    case DRM_MODE_CONNECTOR_DisplayPort: return "DP";
+    case DRM_MODE_CONNECTOR_HDMIA: return "HDMI-A";
+    case DRM_MODE_CONNECTOR_HDMIB: return "HDMI-B";
+    case DRM_MODE_CONNECTOR_DVID: return "DVI-D";
+    case DRM_MODE_CONNECTOR_DVII: return "DVI-I";
+    case DRM_MODE_CONNECTOR_eDP: return "eDP";
+    case DRM_MODE_CONNECTOR_VGA: return "VGA";
+    default: return NULL;
+    }
+}
+
+// The monitor name descriptor (0xFC) of the connector's EDID, which is what
+// GDK's Wayland backend reports as the monitor model.
+static void edid_model_name(int fd, uint32_t connector_id, char *out, size_t size) {
+    out[0] = '\0';
+    drmModeObjectPropertiesPtr props = drmModeObjectGetProperties(fd, connector_id, DRM_MODE_OBJECT_CONNECTOR);
+    if (!props) return;
+    for (uint32_t i = 0; i < props->count_props && !out[0]; i++) {
+        drmModePropertyPtr prop = drmModeGetProperty(fd, props->props[i]);
+        if (prop && strcmp(prop->name, "EDID") == 0 && props->prop_values[i]) {
+            drmModePropertyBlobPtr blob = drmModeGetPropertyBlob(fd, props->prop_values[i]);
+            if (blob && blob->length >= 128) {
+                const unsigned char *edid = blob->data;
+                for (int d = 54; d <= 108; d += 18) {
+                    if (edid[d] || edid[d + 1] || edid[d + 2] || edid[d + 3] != 0xFC) continue;
+                    size_t n = 0;
+                    for (int k = 5; k < 18 && n + 1 < size && edid[d + k] != '\n'; k++) out[n++] = edid[d + k];
+                    while (n && isspace((unsigned char)out[n - 1])) n--;
+                    out[n] = '\0';
+                    break;
+                }
+            }
+            drmModeFreePropertyBlob(blob);
+        }
+        drmModeFreeProperty(prop);
+    }
+    drmModeFreeObjectProperties(props);
+}
+
+drmModeConnectorPtr drmModeGetConnector(int fd, uint32_t connector_id) {
+    static drmModeConnectorPtr (*real)(int, uint32_t);
+    if (!real) real = dlsym(RTLD_NEXT, "drmModeGetConnector");
+    drmModeConnectorPtr connector = real(fd, connector_id);
+    if (!connector || connector->connection != DRM_MODE_CONNECTED || !gtk_resolved()) return connector;
+
+    GdkDisplay *display = gtk.display_get_default();
+    if (!display) return connector;
+
+    char output_name[32] = "";
+    const char *prefix = connector_prefix(connector->connector_type);
+    if (prefix) snprintf(output_name, sizeof output_name, "%s-%u", prefix, connector->connector_type_id);
+    char edid_name[32];
+    edid_model_name(fd, connector_id, edid_name, sizeof edid_name);
+
+    for (int i = 0; i < gtk.display_get_n_monitors(display); i++) {
+        GdkMonitor *monitor = gtk.display_get_monitor(display, i);
+        const char *model = gtk.monitor_get_model(monitor);
+        if (!model) continue;
+        if (!(output_name[0] && strcmp(model, output_name) == 0) && !(edid_name[0] && strcmp(model, edid_name) == 0))
+            continue;
+        int w = gtk.monitor_get_width_mm(monitor), h = gtk.monitor_get_height_mm(monitor);
+        if (w > 0 && h > 0 && ((uint32_t)w != connector->mmWidth || (uint32_t)h != connector->mmHeight)) {
+            debug("%s (%s): connector size %ux%u mm -> %dx%d mm (as GDK reports)\n", output_name, edid_name,
+                  connector->mmWidth, connector->mmHeight, w, h);
+            connector->mmWidth = w;
+            connector->mmHeight = h;
+        }
+        break;
+    }
+    return connector;
+}
+
+// --- 2. Vblank emulation ----------------------------------------------------
+
+struct emulated_crtc {
+    int fd;
+    unsigned index;
+    long long period_ns;
+    struct timespec base;
+};
+
+static struct emulated_crtc crtcs[16];
+static int crtc_count;
+static pthread_mutex_t crtcs_lock = PTHREAD_MUTEX_INITIALIZER;
+
+static long long to_ns(const struct timespec *t) {
+    return (long long)t->tv_sec * 1000000000LL + t->tv_nsec;
+}
+
+static double rate_multiplier(void) {
+    const char *value = getenv("VBLANK_SHIM_RATE_MULTIPLIER");
+    double multiplier = value ? atof(value) : 1.0;
+    return multiplier >= 1.0 ? multiplier : 1.0;
+}
+
+static long long refresh_period_ns(int fd, unsigned index) {
+    long long period = (long long)(1e9 / (60 * rate_multiplier()));
+    drmModeResPtr resources = drmModeGetResources(fd);
+    if (!resources) return period;
+    if ((int)index < resources->count_crtcs) {
+        drmModeCrtcPtr crtc = drmModeGetCrtc(fd, resources->crtcs[index]);
+        if (crtc && crtc->mode_valid && crtc->mode.htotal && crtc->mode.vtotal) {
+            const drmModeModeInfo *mode = &crtc->mode;
+            double hz = mode->clock * 1000.0 / ((double)mode->htotal * mode->vtotal);
+            if (mode->flags & DRM_MODE_FLAG_INTERLACE) hz *= 2;
+            if (mode->flags & DRM_MODE_FLAG_DBLSCAN) hz /= 2;
+            if (mode->vscan > 1) hz /= mode->vscan;
+            if (hz > 1) period = (long long)(1e9 / (hz * rate_multiplier()));
+            debug("emulating vblank for crtc index %u at %.3f Hz x %.1f\n", index, hz, rate_multiplier());
+        }
+        drmModeFreeCrtc(crtc);
+    }
+    drmModeFreeResources(resources);
+    return period;
+}
+
+static struct emulated_crtc *emulated_crtc_for(int fd, unsigned index) {
+    pthread_mutex_lock(&crtcs_lock);
+    struct emulated_crtc *found = NULL;
+    for (int i = 0; i < crtc_count; i++) {
+        if (crtcs[i].fd == fd && crtcs[i].index == index) {
+            found = &crtcs[i];
+            break;
+        }
+    }
+    if (!found && crtc_count < (int)(sizeof crtcs / sizeof crtcs[0])) {
+        found = &crtcs[crtc_count++];
+        found->fd = fd;
+        found->index = index;
+        found->period_ns = refresh_period_ns(fd, index);
+        clock_gettime(CLOCK_MONOTONIC, &found->base);
+    }
+    pthread_mutex_unlock(&crtcs_lock);
+    return found;
+}
+
+int drmWaitVBlank(int fd, drmVBlankPtr vbl) {
+    static int (*real)(int, drmVBlankPtr);
+    if (!real) real = dlsym(RTLD_NEXT, "drmWaitVBlank");
+
+    drmVBlankReq request = vbl->request;
+    int ret = real(fd, vbl);
+    if (ret == 0) return 0;
+
+    int error = errno;
+    // Only stand in for a driver that does not do vblank waits at all, and only
+    // for plain blocking waits.
+    if ((error != EOPNOTSUPP && error != EPERM) || (request.type & (DRM_VBLANK_EVENT | DRM_VBLANK_SIGNAL))) {
+        errno = error;
+        return ret;
+    }
+
+    unsigned index = (request.type & DRM_VBLANK_SECONDARY)
+        ? 1
+        : (request.type & DRM_VBLANK_HIGH_CRTC_MASK) >> DRM_VBLANK_HIGH_CRTC_SHIFT;
+    struct emulated_crtc *crtc = emulated_crtc_for(fd, index);
+    if (!crtc) {
+        errno = error;
+        return ret;
+    }
+
+    struct timespec now;
+    clock_gettime(CLOCK_MONOTONIC, &now);
+    long long base = to_ns(&crtc->base);
+    long long current = (to_ns(&now) - base) / crtc->period_ns;
+    long long target;
+    if (request.type & DRM_VBLANK_RELATIVE) {
+        target = current + request.sequence;
+    } else {
+        target = request.sequence;
+        if (target <= current && (request.type & DRM_VBLANK_NEXTONMISS)) target = current + 1;
+    }
+    if (target < current) target = current;
+
+    long long when = base + target * crtc->period_ns;
+    if (target > current) {
+        struct timespec until = { when / 1000000000LL, when % 1000000000LL };
+        while (clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &until, NULL) == EINTR) {
+        }
+    }
+
+    vbl->reply.type = request.type;
+    vbl->reply.sequence = (unsigned)target;
+    vbl->reply.tval_sec = when / 1000000000LL;
+    vbl->reply.tval_usec = (when % 1000000000LL) / 1000;
+    return 0;
+}
+
+// --- 3. GTK3 frame timings --------------------------------------------------
+
+static gint64 frame_refresh_interval_us;
+// Offset of the refresh_interval field inside GdkFrameTimings, found through
+// the public getter rather than assumed. -1: not found yet, -2: give up.
+static long refresh_interval_offset = -1;
+
+static gint64 monitor_refresh_interval_us(void) {
+    const char *forced = getenv("VBLANK_SHIM_REFRESH_HZ");
+    if (forced && atof(forced) > 1) return (gint64)(1e6 / atof(forced));
+    GdkDisplay *display = gtk.display_get_default();
+    if (!display) return 0;
+    int fastest = 0;
+    for (int i = 0; i < gtk.display_get_n_monitors(display); i++) {
+        int rate = gtk.monitor_get_refresh_rate(gtk.display_get_monitor(display, i));
+        if (rate > fastest) fastest = rate;
+    }
+    // GDK reports milli-hertz.
+    return fastest > 0 ? (gint64)(1000000000LL / fastest) : 0;
+}
+
+static long find_refresh_interval_offset(GdkFrameTimings *timings) {
+    gint64 *slots = (gint64 *)timings;
+    // The struct starts with a guint ref_count; the gint64 fields follow it.
+    for (long offset = 8; offset <= 96; offset += 8) {
+        gint64 saved = slots[offset / 8];
+        slots[offset / 8] = 0x5eed5eed5eedLL;
+        gboolean match = gtk.frame_timings_get_refresh_interval(timings) == 0x5eed5eed5eedLL;
+        slots[offset / 8] = saved;
+        if (match) return offset;
+    }
+    return -2;
+}
+
+static gboolean after_paint_hook(GSignalInvocationHint *hint, guint n_params, const GValue *params, gpointer data) {
+    (void)hint;
+    (void)data;
+    if (n_params < 1 || refresh_interval_offset == -2) return TRUE;
+    GdkFrameTimings *timings = gtk.frame_clock_get_current_timings(gtk.value_get_object(&params[0]));
+    // Only frames the backend left without a refresh interval.
+    if (!timings || gtk.frame_timings_get_refresh_interval(timings) != 0) return TRUE;
+
+    if (!frame_refresh_interval_us) frame_refresh_interval_us = monitor_refresh_interval_us();
+    if (frame_refresh_interval_us <= 0) return TRUE;
+    if (refresh_interval_offset == -1) {
+        refresh_interval_offset = find_refresh_interval_offset(timings);
+        if (refresh_interval_offset < 0) {
+            debug("could not locate refresh_interval in GdkFrameTimings, leaving GTK alone\n");
+            return TRUE;
+        }
+        debug("GTK frame timings: refresh interval %" G_GINT64_FORMAT " us (offset %ld)\n",
+              frame_refresh_interval_us, refresh_interval_offset);
+    }
+    ((gint64 *)timings)[refresh_interval_offset / 8] = frame_refresh_interval_us;
+    return TRUE;
+}
+
+static void install_frame_clock_hook(void) {
+    const char *enabled = getenv("VBLANK_SHIM_FRAME_CLOCK");
+    if (enabled && strcmp(enabled, "0") == 0) return;
+    if (!gtk_resolved()) return;
+    GType type = gtk.frame_clock_get_type();
+    gtk.type_class_ref(type);  // signals exist once the class does; keep it alive
+    guint signal = gtk.signal_lookup("after-paint", type);
+    if (!signal) return;
+    gtk.signal_add_emission_hook(signal, 0, after_paint_hook, NULL, NULL);
+    debug("installed GTK after-paint hook\n");
+}
+
+GdkFrameClock *gdk_window_get_frame_clock(GdkWindow *window) {
+    static GdkFrameClock *(*real)(GdkWindow *);
+    static pthread_once_t once = PTHREAD_ONCE_INIT;
+    if (!real) real = dlsym(RTLD_NEXT, "gdk_window_get_frame_clock");
+    GdkFrameClock *clock = real(window);
+    if (clock) pthread_once(&once, install_frame_clock_hook);
+    return clock;
+}

modrinth-enhanced/.SRCINFO

@@ -1,7 +1,7 @@
 pkgbase = modrinth-enhanced
 	pkgdesc = Modrinth App without ads or telemetry, with offline and Ely.by accounts and Linux fixes
 	pkgver = 0.21.2
-	pkgrel = 1
+	pkgrel = 2
 	url = https://github.com/Felitendo/Modrinth-Enhanced
 	arch = x86_64
 	license = GPL-3.0-only
@@ -19,6 +19,7 @@ pkgbase = modrinth-enhanced
 	depends = glibc
 	depends = gtk3
 	depends = hicolor-icon-theme
+	depends = libdrm
 	depends = libgcc
 	depends = libsoup3
 	depends = webkit2gtk-4.1
@@ -34,7 +35,11 @@ pkgbase = modrinth-enhanced
 	options = !debug
 	source = modrinth-enhanced-v0.21.2.tar.gz::https://github.com/Felitendo/Modrinth-Enhanced/archive/refs/tags/v0.21.2.tar.gz
 	source = modrinth-code-v0.21.2.tar.gz::https://github.com/modrinth/code/archive/refs/tags/v0.21.2.tar.gz
+	source = vblank-shim.c
+	source = modrinth-enhanced.sh
 	sha256sums = a87ddcef0a39ab4a2c56ece806e381c6b398c755da00a9734b0162abc377e5a6
 	sha256sums = 583e085cd7ae64a7020656af4ecc64ecfcc82fd97519f74cc3ab114d49574a5e
+	sha256sums = 0190921b8ff2fb1deec3209cba71c01541ca1f013e3ba41680f1636e185fd455
+	sha256sums = b24872f82645c52ee4804599cd678d138876fb193c754403fa9c5cf92bd745b9
 
 pkgname = modrinth-enhanced

modrinth-enhanced/PKGBUILD

@@ -4,13 +4,13 @@
 
 pkgname=modrinth-enhanced
 pkgver=0.21.2
-pkgrel=1
+pkgrel=2
 pkgdesc="Modrinth App without ads or telemetry, with offline and Ely.by accounts and Linux fixes"
 arch=('x86_64')
 url="https://github.com/Felitendo/Modrinth-Enhanced"
 license=('GPL-3.0-only')
 depends=('cairo' 'dbus' 'gdk-pixbuf2' 'glib2' 'glibc' 'gtk3' 'hicolor-icon-theme'
-         'libgcc' 'libsoup3' 'webkit2gtk-4.1'
+         'libdrm' 'libgcc' 'libsoup3' 'webkit2gtk-4.1'
          # loaded by Minecraft, not by the launcher
          'libgl' 'libpulse' 'libx11' 'libxcursor' 'libxext' 'libxxf86vm')
 # git replays the patches the way upstream's scripts/prepare.sh does; the JDK
@@ -27,14 +27,20 @@ options=('!lto' '!debug')
 _tag="v0.21.2"
 _upstream="v0.21.2"
 _base="v0.21.2"
+# With the NVIDIA driver WebKitGTK paces the app with a 60 fps timer whatever
+# the monitor's refresh rate. vblank-shim.c, preloaded by modrinth-enhanced.sh,
+# paces it at the monitor's rate instead and keeps the app on X11, the only
+# place that works; it is not part of upstream's release.
 source=("${pkgname}-${_tag}.tar.gz::https://github.com/Felitendo/Modrinth-Enhanced/archive/refs/tags/${_tag}.tar.gz"
-        "modrinth-code-${_upstream}.tar.gz::https://github.com/modrinth/code/archive/refs/tags/${_upstream}.tar.gz")
+        "modrinth-code-${_upstream}.tar.gz::https://github.com/modrinth/code/archive/refs/tags/${_upstream}.tar.gz"
+        "vblank-shim.c"
+        "modrinth-enhanced.sh")
 noextract=("modrinth-code-${_upstream}.tar.gz")
 if [[ "$_base" != "$_upstream" ]]; then
   source+=("modrinth-code-${_base}.tar.gz::https://github.com/modrinth/code/archive/refs/tags/${_base}.tar.gz")
   noextract+=("modrinth-code-${_base}.tar.gz")
 fi
-sha256sums=('a87ddcef0a39ab4a2c56ece806e381c6b398c755da00a9734b0162abc377e5a6' '583e085cd7ae64a7020656af4ecc64ecfcc82fd97519f74cc3ab114d49574a5e')
+sha256sums=('a87ddcef0a39ab4a2c56ece806e381c6b398c755da00a9734b0162abc377e5a6' '583e085cd7ae64a7020656af4ecc64ecfcc82fd97519f74cc3ab114d49574a5e' '0190921b8ff2fb1deec3209cba71c01541ca1f013e3ba41680f1636e185fd455' 'b24872f82645c52ee4804599cd678d138876fb193c754403fa9c5cf92bd745b9')
 
 prepare() {
   # What upstream's scripts/prepare.sh does with two shallow tags: apply the
@@ -88,6 +94,10 @@ prepare() {
 }
 
 build() {
+  # GLib for its headers only: the shim looks GTK and GLib up at run time
+  gcc $CPPFLAGS $CFLAGS $LDFLAGS -shared -fPIC -o libwebkit-vblank-shim.so vblank-shim.c \
+    $(pkg-config --cflags glib-2.0) $(pkg-config --cflags --libs libdrm)
+
   cd app
 
   export RUSTUP_TOOLCHAIN=stable
@@ -106,8 +116,11 @@ build() {
 package() {
   cd app
 
-  # the same files, under the same names, as upstream's .deb
+  # the same files, under the same names, as modrinth-enhanced-bin: the binary
-  install -Dm755 target/release/ModrinthEnhanced -t "$pkgdir/usr/bin/"
+  # sits behind the script that preloads the shim
+  install -Dm755 target/release/ModrinthEnhanced -t "$pkgdir/usr/lib/modrinth-enhanced/"
+  install -Dm755 "$srcdir/libwebkit-vblank-shim.so" -t "$pkgdir/usr/lib/modrinth-enhanced/"
+  install -Dm755 "$srcdir/modrinth-enhanced.sh" "$pkgdir/usr/bin/ModrinthEnhanced"
   ln -s ModrinthEnhanced "$pkgdir/usr/bin/modrinth-enhanced"
 
   install -Dm644 apps/app/icons/128x128.png \

modrinth-enhanced/modrinth-enhanced.sh

@@ -0,0 +1 @@
+../modrinth-enhanced-bin/modrinth-enhanced.sh

modrinth-enhanced/pkg.sh

@@ -23,7 +23,7 @@ UPSTREAM_REPO="Felitendo/Modrinth-Enhanced"
 
 # Installed in CI (pacman) before the makepkg test build. makepkg runs with
 # -d there, so the libraries the binary links against are listed too.
-BUILD_DEPS=(rust git jdk17-openjdk node-gyp nodejs npm pnpm webkit2gtk-4.1 gtk3 libsoup3)
+BUILD_DEPS=(rust git jdk17-openjdk node-gyp nodejs npm pnpm webkit2gtk-4.1 gtk3 libsoup3 libdrm)
 
 latest_version() {
   gh api "repos/$UPSTREAM_REPO/releases/latest" --jq '.tag_name' | sed 's/^v//; s/-/.r/'
@@ -52,7 +52,11 @@ refresh_checksums() {
     | sha256sum | cut -d' ' -f1)"
   sha_upstream="$(curl -sfL "https://github.com/modrinth/code/archive/refs/tags/$upstream.tar.gz" \
     | sha256sum | cut -d' ' -f1)"
+  # vblank-shim.c and modrinth-enhanced.sh ship with the package, as symlinks
+  # to modrinth-enhanced-bin's copies; they come before the optional base tag
   sums="'$sha_patches' '$sha_upstream'"
+  sums+=" '$(sha256sum "$(dirname "$pkgbuild")/vblank-shim.c" | cut -d' ' -f1)'"
+  sums+=" '$(sha256sum "$(dirname "$pkgbuild")/modrinth-enhanced.sh" | cut -d' ' -f1)'"
   if [[ "$base" != "$upstream" ]]; then
     sums+=" '$(curl -sfL "https://github.com/modrinth/code/archive/refs/tags/$base.tar.gz" \
       | sha256sum | cut -d' ' -f1)'"

modrinth-enhanced/vblank-shim.c

@@ -0,0 +1 @@
+../modrinth-enhanced-bin/vblank-shim.c