fix(lock): hold sleep inhibitor until compositor confirms lock (#2907)

lock-before-suspend released the logind sleep delay inhibitor as soon as Qt
reported the lock rendered (afterAnimating/afterRendering). That signal fires
before the compositor has committed/presented the ext-session-lock surface, so
the machine could freeze ~1 frame later with the desktop still the last
presented frame. On resume the desktop was briefly visible before the lock
appeared (both suspend and hibernate).

Gate lockerReady on WlSessionLock.secure (the ext-session-lock `locked` event),
so the inhibitor is held until the compositor confirms the session is locked and
the desktop is hidden. LockSurface passes the WlSessionLock down as sessionLock;
the readiness check returns early until secure, and re-fires on secureChanged.
The Go-side fallback timer in loginctl monitor remains as the backstop.

Reproduced on niri / s2idle with 3 outputs: debug log showed lockerReady sent
18 ms before `PM: suspend entry`; with this change the desktop no longer flashes
on resume.

Signed-off-by: Thomas Kroll <99196436+tkroll-ionos@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

quickshell/Modules/Lock/LockScreenContent.qml

@@ -36,6 +36,7 @@ Item {
     property int hyprlandLayoutCount: 0
     property bool lockerReadySent: false
     property bool lockerReadyArmed: false
+    property var sessionLock: null
     readonly property bool hasCustomWallpaper: SettingsData.lockScreenWallpaperPath !== ""
     readonly property string lockFontFamily: SettingsData.lockScreenFontFamily
 
@@ -134,12 +135,27 @@ Item {
             return;
         if (!root.visible || root.opacity <= 0)
             return;
+        // Don't report ready until the compositor has confirmed the session is
+        // locked (ext-session-lock `locked` event). Qt's afterRendering fires
+        // before the lock surface is committed/presented, so releasing the sleep
+        // inhibitor on it lets the machine freeze with the desktop still on screen,
+        // which then flashes on resume. secure=true guarantees the desktop is hidden.
+        if (root.sessionLock && !root.sessionLock.secure)
+            return;
         Qt.callLater(() => {
             if (root.visible && root.opacity > 0 && !root.unlocking)
                 sendLockerReadyOnce();
         });
     }
 
+    Connections {
+        target: root.sessionLock
+        enabled: target !== null
+        function onSecureChanged() {
+            root.maybeSend();
+        }
+    }
+
     Connections {
         target: root.Window.window
         enabled: target !== null

quickshell/Modules/Lock/LockSurface.qml

@@ -33,6 +33,7 @@ FocusScope {
 
         anchors.fill: parent
         demoMode: false
+        sessionLock: root.lock
         pam: root.pam
         passwordBuffer: root.sharedPasswordBuffer
         screenName: root.screenName