Bug 1240065 - Throttle repaints when pinch zooming r=botond

gfx/layers/apz/src/AsyncPanZoomController.cpp

@@ -365,6 +365,12 @@ typedef GenericFlingAnimation FlingAnimation;
  * \li\b apz.zoom_animation_duration_ms
  * This controls how long the zoom-to-rect animation takes.\n
  * Units: ms
+ *
+ * \li\b apz.scale_repaint_delay_ms
+ * How long to delay between repaint requests during a scale.
+ * A negative number prevents repaint requests during a scale.\n
+ * Units: ms
+ *
  */
 
 /**
@@ -703,6 +709,7 @@ AsyncPanZoomController::AsyncPanZoomController(uint64_t aLayersId,
      mState(NOTHING),
      mNotificationBlockers(0),
      mInputQueue(aInputQueue),
+     mPinchPaintTimerSet(false),
      mAPZCId(sAsyncPanZoomControllerCount++),
      mSharedLock(nullptr),
      mAsyncTransformAppliedToContent(false),
@@ -1281,6 +1288,7 @@ nsEventStatus AsyncPanZoomController::OnTouchCancel(const MultiTouchInput& aEven
 nsEventStatus AsyncPanZoomController::OnScaleBegin(const PinchGestureInput& aEvent) {
   APZC_LOG("%p got a scale-begin in state %d\n", this, mState);
 
+  mPinchPaintTimerSet = false;
   // Note that there may not be a touch block at this point, if we received the
   // PinchGestureEvent directly from widget code without any touch events.
   if (HasReadyTouchBlock() && !CurrentTouchBlock()->TouchActionAllowsPinchZoom()) {
@@ -1375,8 +1383,21 @@ nsEventStatus AsyncPanZoomController::OnScale(const PinchGestureInput& aEvent) {
       }
 
       ScheduleComposite();
-      // We don't want to redraw on every scale, so don't use
-      // RequestContentRepaint()
+
+      // We don't want to redraw on every scale, so throttle it.
+      if (!mPinchPaintTimerSet) {
+        const int delay = gfxPrefs::APZScaleRepaintDelay();
+        if (delay >= 0) {
+          if (RefPtr<GeckoContentController> controller = GetGeckoContentController()) {
+            mPinchPaintTimerSet = true;
+            controller->PostDelayedTask(
+              NewRunnableMethod(this,
+                                &AsyncPanZoomController::DoDelayedRequestContentRepaint),
+              delay);
+          }
+        }
+      }
+
       UpdateSharedCompositorFrameMetrics();
     }
 
@@ -1389,6 +1410,8 @@ nsEventStatus AsyncPanZoomController::OnScale(const PinchGestureInput& aEvent) {
 nsEventStatus AsyncPanZoomController::OnScaleEnd(const PinchGestureInput& aEvent) {
   APZC_LOG("%p got a scale-end in state %d\n", this, mState);
 
+  mPinchPaintTimerSet = false;
+
   if (HasReadyTouchBlock() && !CurrentTouchBlock()->TouchActionAllowsPinchZoom()) {
     return nsEventStatus_eIgnore;
   }
@@ -1613,6 +1636,15 @@ AsyncPanZoomController::AllowScrollHandoffInCurrentBlock() const
   return result;
 }
 
+void AsyncPanZoomController::DoDelayedRequestContentRepaint()
+{
+  if (!IsDestroyed() && mPinchPaintTimerSet) {
+    ReentrantMonitorAutoEnter lock(mMonitor);
+    RequestContentRepaint();
+  }
+  mPinchPaintTimerSet = false;
+}
+
 static ScrollInputMethod
 ScrollInputMethodForWheelDeltaType(ScrollWheelInput::ScrollDeltaType aDeltaType)
 {

gfx/layers/apz/src/AsyncPanZoomController.h

@@ -898,6 +898,8 @@ private:
   ParentLayerPoint mLastFlingVelocity;
   // The time at which the most recent fling started.
   TimeStamp mLastFlingTime;
+  // Indicates if the repaint-during-pinch timer is currently set
+  bool mPinchPaintTimerSet;
 
   // Deal with overscroll resulting from a fling animation. This is only ever
   // called on APZC instances that were actually performing a fling.
@@ -921,6 +923,9 @@ private:
   // Returns whether overscroll is allowed during an event.
   bool AllowScrollHandoffInCurrentBlock() const;
 
+  // Invoked by the pinch repaint timer.
+  void DoDelayedRequestContentRepaint();
+
   /* ===================================================================
    * The functions and members in this section are used to make ancestor chains
    * out of APZC instances. These chains can only be walked or manipulated

gfx/thebes/gfxPrefs.h

@@ -187,6 +187,7 @@ private:
   DECL_GFX_PREF(Live, "apz.y_skate_size_multiplier",           APZYSkateSizeMultiplier, float, 2.5f);
   DECL_GFX_PREF(Live, "apz.y_stationary_size_multiplier",      APZYStationarySizeMultiplier, float, 3.5f);
   DECL_GFX_PREF(Live, "apz.zoom_animation_duration_ms",        APZZoomAnimationDuration, int32_t, 250);
+  DECL_GFX_PREF(Live, "apz.scale_repaint_delay_ms",            APZScaleRepaintDelay, int32_t, 500);
 
   DECL_GFX_PREF(Live, "browser.ui.zoom.force-user-scalable",   ForceUserScalable, bool, false);
   DECL_GFX_PREF(Live, "browser.viewport.desktopWidth",         DesktopViewportWidth, int32_t, 980);

modules/libpref/init/all.js

@@ -644,6 +644,7 @@ pref("apz.y_skate_size_multiplier", "3.5");
 pref("apz.x_stationary_size_multiplier", "1.5");
 pref("apz.y_stationary_size_multiplier", "3.5");
 pref("apz.zoom_animation_duration_ms", 250);
+pref("apz.scale_repaint_delay_ms", 500);
 
 #if defined(MOZ_WIDGET_GONK) || defined(MOZ_WIDGET_ANDROID)
 // Mobile prefs