feat: open gtklock from outside once it can

README.md

@@ -83,8 +83,9 @@ switches it on; right after installing, log out and back in once.
 On Hyprland and Niri the lock screen is a program of your choice, and only it
 can open itself. So face-unlock goes into its password check, as with sudo:
 press Enter on the empty password field to scan. hyprlock and swaylock also
-scan by themselves when you come back. Those lock screens cover the bubble,
-which shows the tick once they are gone.
+scan by themselves when you come back, and so does gtklock after 4.0.0 (the
+first to open from outside). Those lock screens cover the bubble, which shows
+the tick once they are gone. gtklock shows face unlock's messages.
 
 For the bubble on the lock screen, use face-unlock's own: `face-unlock lock`.
 It shows the wallpaper of your desktop (from swaybg, awww, hyprpaper or

doc/face-unlock.1.scd

@@ -201,8 +201,9 @@ does not start a scan with every key.
 
 When the face matches, the agent unlocks the session the way its lock screen
 wants it: through logind, as *loginctl unlock-session* does, on Plasma and
-GNOME, by itself on its own lock screen, and with SIGUSR1 for hyprlock and
-swaylock. Any other lock screen opens itself, through PAM (see *DESKTOPS*).
+GNOME, by itself on its own lock screen, and with SIGUSR1 for hyprlock,
+swaylock and gtklock after 4.0.0. Any other lock screen opens itself, through
+PAM (see *DESKTOPS*).
 
 Unlocked through logind, Plasma's lock screen cuts off its own password prompt
 and counts that as a wrong password. After a face unlock the daemon resets the
@@ -241,10 +242,13 @@ so does the bubble, above the lock screen too.
 	open itself. hyprlock asks PAM the moment it starts; that first time
 	is skipped, so a screen locked on purpose does not open again at once.
 
-	hyprlock and swaylock can also be opened from outside: the agent finds
-	them among the user's processes (niri also sets *LockedHint*), scans
-	when somebody comes back, and opens them with SIGUSR1. Those lock
-	screens cover the bubble, which shows the tick once they are gone.
+	hyprlock, swaylock and gtklock (after 4.0.0) can also be opened from
+	outside: the agent finds them among the user's processes (niri also
+	sets *LockedHint*), scans when somebody comes back, and opens them with
+	SIGUSR1. It only does so once the lock screen handles SIGUSR1: before
+	it has locked, the signal would kill it. Those lock screens cover the
+	bubble, which shows the tick once they are gone. gtklock shows the
+	messages of the PAM module.
 
 	For the bubble on the lock screen there is face-unlock's own: *lock*.
 	It shows the time, a password field (PAM service _face-unlock-lock_

src/agent/lockcontroller.cpp

@@ -42,6 +42,14 @@ LockController::LockController(BubbleController *bubble, UserConfig *config, Ses
     });
     connect(&m_input, &InputWatcher::input, this, &LockController::onResume);
     connect(&m_lock, &LockWatcher::lockedChanged, this, &LockController::onLockedChanged);
+    // A lock screen that is only starting cannot be opened yet: the scan
+    // that was due when it locked follows once it can.
+    connect(&m_lock, &LockWatcher::unlockable, this, [this] {
+        if (m_lockScanDue) {
+            m_lockScanDue = false;
+            startScan(QStringLiteral("lock"));
+        }
+    });
 
     QDBusConnection::systemBus().connect(QStringLiteral("org.freedesktop.login1"),
                                          QStringLiteral("/org/freedesktop/login1"),
@@ -58,6 +66,7 @@ void LockController::onLockedChanged(bool locked)
     }
     if (!locked) {
         m_locked = false;
+        m_lockScanDue = false;
         m_armTimer.stop();
         m_input.stop();
         if (m_scan) {
@@ -90,6 +99,7 @@ void LockController::onLockedChanged(bool locked)
 
     if (m_config->scanOnLock()) {
         QTimer::singleShot(400, this, [this] {
+            m_lockScanDue = m_locked && !m_lock.canUnlock();
             startScan(QStringLiteral("lock"));
         });
     } else {

src/agent/lockcontroller.h

@@ -59,6 +59,8 @@ private:
     LockScreenController *m_screen;
     bool m_locked = false;
     bool m_stopped = false;
+    // Scan right after locking, once the lock screen can be opened.
+    bool m_lockScanDue = false;
     QElapsedTimer m_lockedFor;
     QPointer<DaemonRequest> m_scan;
     QTimer m_armTimer;

src/agent/lockers.cpp

@@ -5,6 +5,7 @@
 #include <QFile>
 #include <QString>
 
+#include <algorithm>
 #include <csignal>
 #include <dirent.h>
 #include <sys/stat.h>
@@ -14,7 +15,7 @@ namespace
 {
 bool isLocker(const QByteArray &name)
 {
-    return name == "hyprlock" || name == "swaylock";
+    return name == "hyprlock" || name == "swaylock" || name == "gtklock";
 }
 
 QByteArray readFile(const QString &path)
@@ -33,9 +34,9 @@ pid_t parentOf(pid_t pid)
 
 // The lock screens of this user on this display. Another session of the same
 // user has a display of its own, and its lock screen is left alone. A child
-// of a lock screen (swaylock checks the password in one) is left out: killed
-// by the signal before its parent unlocks, it would take the parent down
-// with it, and the screen would stay locked.
+// of a lock screen (swaylock and gtklock check the password in one) is left
+// out: killed by the signal before its parent unlocks, it would take the
+// parent down with it, and the screen would stay locked.
 QList<pid_t> findAll()
 {
     QList<pid_t> found;
@@ -104,6 +105,14 @@ QList<pid_t> Lockers::find(const QByteArray &name)
     return found;
 }
 
+bool Lockers::ready(int sig)
+{
+    const QList<pid_t> lockers = find();
+    return std::any_of(lockers.cbegin(), lockers.cend(), [sig](pid_t pid) {
+        return catches(pid, sig);
+    });
+}
+
 int Lockers::signal(int sig, const QByteArray &name)
 {
     int waiting = 0;

src/agent/lockers.h

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 //
 // The lock screens that are programs of their own and take signals from
-// outside: hyprlock and swaylock open on SIGUSR1.
+// outside: hyprlock, swaylock and gtklock open on SIGUSR1.
 
 #pragma once
 
@@ -19,4 +19,7 @@ QList<pid_t> find(const QByteArray &name = {});
 // that, the signal kills it, and the compositor keeps the screen locked with
 // nobody to open it.
 int signal(int sig, const QByteArray &name = {});
+// Whether one of them handles sig: gtklock only opens on SIGUSR1 since 2025,
+// and none does before it has locked.
+bool ready(int sig);
 }

src/agent/lockwatcher.cpp

@@ -160,7 +160,13 @@ void LockWatcher::onSessionProperties(const QString &interface, const QVariantMa
 void LockWatcher::pollLockers()
 {
     m_lockerRunning = !Lockers::find().isEmpty();
+    const bool ready = Lockers::ready(SIGUSR1);
+    const bool became = ready && !m_lockerReady;
+    m_lockerReady = ready;
     update();
+    if (became) {
+        Q_EMIT unlockable();
+    }
 }
 
 void LockWatcher::setOwnLock(SessionLock *lock)
@@ -171,7 +177,7 @@ void LockWatcher::setOwnLock(SessionLock *lock)
 
 bool LockWatcher::canUnlock() const
 {
-    return (m_own && m_own->isLocked()) || !m_ownLockers || m_lockerRunning;
+    return (m_own && m_own->isLocked()) || !m_ownLockers || m_lockerReady;
 }
 
 void LockWatcher::update()

src/agent/lockwatcher.h

@@ -7,11 +7,12 @@
 //   GNOME     logind's LockedHint. Unlocked through logind.
 //   Niri      logind's LockedHint, which niri sets for any lock screen.
 //   Hyprland  sets no LockedHint, so the lock screen is looked for among this
-//             user's processes (hyprlock, swaylock) once a second. Only on
-//             compositors where the lock screen is a program of its own
-//             (ext-session-lock).
+//             user's processes (hyprlock, swaylock, gtklock) once a second.
+//             Only on compositors where the lock screen is a program of its
+//             own (ext-session-lock).
 //
-// hyprlock and swaylock do not listen to logind. They unlock on SIGUSR1.
+// hyprlock, swaylock and gtklock do not listen to logind. They unlock on
+// SIGUSR1.
 // face-unlock's own lock screen (SessionLock) is simply told to. Any other
 // lock screen of that kind only opens itself: it gets the face through the
 // PAM module in its own stack (see src/lib/pam.sh), when Enter is pressed.
@@ -41,13 +42,16 @@ public:
         return m_locked;
     }
     // Whether unlock() can open the lock screen that is up: always where
-    // logind unlocks (Plasma, GNOME), only hyprlock and swaylock elsewhere.
+    // logind unlocks (Plasma, GNOME), elsewhere only hyprlock, swaylock and
+    // gtklock, once they take SIGUSR1.
     bool canUnlock() const;
     void unlock();
     void setOwnLock(SessionLock *lock);
 
 Q_SIGNALS:
     void lockedChanged(bool locked);
+    // canUnlock() came true: the lock screen that is up now takes SIGUSR1.
+    void unlockable();
 
 private Q_SLOTS:
     void onScreenSaver(bool active);
@@ -63,6 +67,7 @@ private:
     bool m_screenSaver = false;
     bool m_lockedHint = false;
     bool m_lockerRunning = false;
+    bool m_lockerReady = false;
     bool m_locked = false;
     // The compositor's lock screen is a program of its own.
     bool m_ownLockers = false;

tests/test_lockers.cpp

@@ -95,6 +95,7 @@ int main(int, char **argv)
     pid_t pid = fakeHyprlock(false, &from);
     check(Lockers::find("hyprlock") == QList<pid_t>{pid}, "finds the lock screen on this display");
     check(Lockers::find("swaylock").isEmpty(), "and only by that name");
+    check(!Lockers::ready(SIGUSR2), "not ready while it does not handle the signal");
     check(Lockers::signal(SIGUSR2, "hyprlock") == 1, "one not ready yet");
     usleep(200 * 1000);
     check(alive(pid), "and it was left alone, alive");
@@ -103,6 +104,7 @@ int main(int, char **argv)
     close(from);
 
     pid = fakeHyprlock(true, &from);
+    check(Lockers::ready(SIGUSR2), "ready once it does");
     check(Lockers::signal(SIGUSR2, "hyprlock") == 0, "a ready one gets it");
     check(next(from) == 's', "and handles it");
     check(alive(pid), "and lives on");