Remove composite reset timer

Summary:
To streamline Compositor code more remove the composite reset timer. The two
times it was used we can either use a singleshot timer instead or connect the
call to a different signal in the X11 backend.

Long term goal is to have a well structured init of the Compositor such that
we can call directly instead.

Test Plan: Manually in X and Wayland nested session.

Reviewers: #kwin, zzag

Reviewed By: #kwin, zzag

Subscribers: zzag, kwin

Tags: #kwin

Maniphest Tasks: T11071

Differential Revision: https://phabricator.kde.org/D22270

composite.cpp

@@ -110,9 +110,8 @@ Compositor::Compositor(QObject* workspace)
     , m_composeAtSwapCompletion(false)
 {
     qRegisterMetaType<Compositor::SuspendReason>("Compositor::SuspendReason");
-    connect(&compositeResetTimer, &QTimer::timeout, this, &Compositor::reinitialize);
     connect(options, &Options::configChanged, this, &Compositor::slotConfigChanged);
-    compositeResetTimer.setSingleShot(true);
+
     m_monotonicClock.start();
 
     // 2 sec which should be enough to restart the compositor
@@ -816,11 +815,6 @@ bool Compositor::windowRepaintsPending() const
     return false;
 }
 
-void Compositor::setCompositeResetTimer(int msecs)
-{
-    compositeResetTimer.start(msecs);
-}
-
 void Compositor::setCompositeTimer()
 {
     if (!hasScene())  // should not really happen, but there may be e.g. some damage events still pending

composite.h

@@ -125,7 +125,6 @@ public:
     int xrrRefreshRate() const {
         return m_xrrRefreshRate;
     }
-    void setCompositeResetTimer(int msecs);
 
     bool hasScene() const {
         return m_scene != NULL;
@@ -219,7 +218,6 @@ private:
     int m_xrrRefreshRate;
     QRegion repaints_region;
 
-    QTimer compositeResetTimer; // for compressing composite resets
     bool m_finishing; // finish() sets this variable while shutting down
     bool m_starting; // start() sets this variable while starting
     qint64 m_timeSinceLastVBlank;

plugins/platforms/x11/standalone/screens_xrandr.cpp

@@ -47,6 +47,21 @@ void XRandRScreens::init()
     m_backend->initOutputs();
     setCount(m_backend->outputs().count());
     emit changed();
+
+#ifndef KWIN_UNIT_TEST
+    connect(this, &XRandRScreens::changed, this, [] {
+        if (!workspace()->compositing()) {
+            return;
+        }
+        if (Compositor::self()->xrrRefreshRate() == Options::currentRefreshRate()) {
+            return;
+        }
+        // desktopResized() should take care of when the size or
+        // shape of the desktop has changed, but we also want to
+        // catch refresh rate changes
+        Compositor::self()->reinitialize();
+    });
+#endif
 }
 
 void XRandRScreens::updateCount()
@@ -75,15 +90,6 @@ bool XRandRScreens::event(xcb_generic_event_t *event)
         screen->width_in_millimeters = xrrEvent->mwidth;
         screen->height_in_millimeters = xrrEvent->mheight;
     }
-#ifndef KWIN_UNIT_TEST
-    if (workspace()->compositing()) {
-        // desktopResized() should take care of when the size or
-        // shape of the desktop has changed, but we also want to
-        // catch refresh rate changes
-        if (Compositor::self()->xrrRefreshRate() != Options::currentRefreshRate())
-            Compositor::self()->setCompositeResetTimer(0);
-    }
-#endif
 
     return false;
 }