ThreadedCoordinatedLayerTreeHost::renderNextFrame() should short-cut …

…to layer flushing

https://bugs.webkit.org/show_bug.cgi?id=157614

Reviewed by Carlos Garcia Campos.

CoordinatedLayerTreeHost prevents any layer flushes while a previously-commited scene
state is still being rendered on the composition thread. renderNextFrame() is called
once that is complete, and a new layer flush is scheduled.

This change improves the whole ordeal by immediately performing the layer flush only if
it was requested during the time we were waiting on the renderer (i.e. when the latest
scene state was being composited), instead of scheduling it unconditionally.
m_scheduledWhileWaitingForRenderer member variable is added to track that occurrence.

* WebProcess/WebPage/CoordinatedGraphics/CoordinatedLayerTreeHost.cpp:
(WebKit::CoordinatedLayerTreeHost::scheduleLayerFlush):
(WebKit::CoordinatedLayerTreeHost::renderNextFrame):
* WebProcess/WebPage/CoordinatedGraphics/CoordinatedLayerTreeHost.h:


Canonical link: https://commits.webkit.org/183990@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@210545 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Source/WebKit2/ChangeLog

@@ -1,3 +1,24 @@
+2017-01-10  Zan Dobersek  <zdobersek@igalia.com>
+
+        ThreadedCoordinatedLayerTreeHost::renderNextFrame() should short-cut to layer flushing
+        https://bugs.webkit.org/show_bug.cgi?id=157614
+
+        Reviewed by Carlos Garcia Campos.
+
+        CoordinatedLayerTreeHost prevents any layer flushes while a previously-commited scene
+        state is still being rendered on the composition thread. renderNextFrame() is called
+        once that is complete, and a new layer flush is scheduled.
+
+        This change improves the whole ordeal by immediately performing the layer flush only if
+        it was requested during the time we were waiting on the renderer (i.e. when the latest
+        scene state was being composited), instead of scheduling it unconditionally.
+        m_scheduledWhileWaitingForRenderer member variable is added to track that occurrence.
+
+        * WebProcess/WebPage/CoordinatedGraphics/CoordinatedLayerTreeHost.cpp:
+        (WebKit::CoordinatedLayerTreeHost::scheduleLayerFlush):
+        (WebKit::CoordinatedLayerTreeHost::renderNextFrame):
+        * WebProcess/WebPage/CoordinatedGraphics/CoordinatedLayerTreeHost.h:
+
 2017-01-09  Chris Dumez  <cdumez@apple.com>
 
         [iOS] Drop VNodeTracker

Source/WebKit2/WebProcess/WebPage/CoordinatedGraphics/CoordinatedLayerTreeHost.cpp

@@ -78,6 +78,11 @@ void CoordinatedLayerTreeHost::scheduleLayerFlush()
     if (!m_layerFlushSchedulingEnabled)
         return;
 
+    if (m_isWaitingForRenderer) {
+        m_scheduledWhileWaitingForRenderer = true;
+        return;
+    }
+
     if (!m_layerFlushTimer.isActive())
         m_layerFlushTimer.startOneShot(0);
 }
@@ -146,8 +151,13 @@ void CoordinatedLayerTreeHost::setVisibleContentsRect(const FloatRect& rect, con
 void CoordinatedLayerTreeHost::renderNextFrame()
 {
     m_isWaitingForRenderer = false;
-    scheduleLayerFlush();
+    bool scheduledWhileWaitingForRenderer = std::exchange(m_scheduledWhileWaitingForRenderer, false);
     m_coordinator.renderNextFrame();
+
+    if (scheduledWhileWaitingForRenderer || m_layerFlushTimer.isActive()) {
+        m_layerFlushTimer.stop();
+        layerFlushTimerFired();
+    }
 }
 
 void CoordinatedLayerTreeHost::didFlushRootLayer(const FloatRect& visibleContentRect)

Source/WebKit2/WebProcess/WebPage/CoordinatedGraphics/CoordinatedLayerTreeHost.h

@@ -86,6 +86,7 @@ class CoordinatedLayerTreeHost : public LayerTreeHost, public CompositingCoordin
 
     CompositingCoordinator m_coordinator;
     bool m_isWaitingForRenderer { true };
+    bool m_scheduledWhileWaitingForRenderer { false };
     uint64_t m_forceRepaintAsyncCallbackID { 0 };
     RunLoop::Timer<CoordinatedLayerTreeHost> m_layerFlushTimer;
 };