Bug 1257369 - Suppress the DisplayPort when scrolling via nsSliderFrame. r=kats

MozReview-Commit-ID: 8I3UfWlkdPq

--HG--
extra : rebase_source : 25b496ff5f3be9187cb8727982eaa094f85a0d1f

layout/xul/nsSliderFrame.cpp

@@ -22,11 +22,13 @@
 #include "nsHTMLParts.h"
 #include "nsIPresShell.h"
 #include "nsCSSRendering.h"
+#include "nsIDOMEvent.h"
 #include "nsIDOMMouseEvent.h"
 #include "nsScrollbarButtonFrame.h"
 #include "nsISliderListener.h"
 #include "nsIScrollableFrame.h"
 #include "nsIScrollbarMediator.h"
+#include "nsISupportsImpl.h"
 #include "nsScrollbarFrame.h"
 #include "nsRepeatService.h"
 #include "nsBoxLayoutState.h"
@@ -35,16 +37,19 @@
 #include "nsContentUtils.h"
 #include "nsLayoutUtils.h"
 #include "nsDisplayList.h"
+#include "mozilla/Assertions.h"         // for MOZ_ASSERT
 #include "mozilla/Preferences.h"
 #include "mozilla/LookAndFeel.h"
 #include "mozilla/MouseEvents.h"
 #include "mozilla/Telemetry.h"
+#include "mozilla/layers/APZCCallbackHelper.h"
 #include "mozilla/layers/AsyncDragMetrics.h"
 #include "mozilla/layers/InputAPZContext.h"
 #include "mozilla/layers/ScrollInputMethods.h"
 #include <algorithm>
 
 using namespace mozilla;
+using mozilla::layers::APZCCallbackHelper;
 using mozilla::layers::AsyncDragMetrics;
 using mozilla::layers::InputAPZContext;
 using mozilla::layers::ScrollInputMethod;
@@ -80,13 +85,20 @@ nsSliderFrame::nsSliderFrame(nsStyleContext* aContext):
   mChange(0),
   mDragFinished(true),
   mUserChanged(false),
-  mScrollingWithAPZ(false)
+  mScrollingWithAPZ(false),
+  mSuppressionActive(false)
 {
 }
 
 // stop timer
 nsSliderFrame::~nsSliderFrame()
 {
+  MOZ_ASSERT(!mSuppressionActive, "Should have un-suppress via StopDrag() first.");
+  if (mSuppressionActive) {
+    APZCCallbackHelper::SuppressDisplayport(false, PresContext() ?
+                                                   PresContext()->PresShell() :
+                                                   nullptr);
+  }
 }
 
 void
@@ -1042,6 +1054,12 @@ nsSliderFrame::StartDrag(nsIDOMEvent* aEvent)
   printf("Pressed mDragStart=%d\n",mDragStart);
 #endif
 
+  if (!mScrollingWithAPZ && !mSuppressionActive) {
+    MOZ_ASSERT(PresContext()->PresShell());
+    APZCCallbackHelper::SuppressDisplayport(true, PresContext()->PresShell());
+    mSuppressionActive = true;
+  }
+
   return NS_OK;
 }
 
@@ -1053,6 +1071,12 @@ nsSliderFrame::StopDrag()
 
   mScrollingWithAPZ = false;
 
+  if (mSuppressionActive) {
+    MOZ_ASSERT(PresContext()->PresShell());
+    APZCCallbackHelper::SuppressDisplayport(false, PresContext()->PresShell());
+    mSuppressionActive = false;
+  }
+
 #ifdef MOZ_WIDGET_GTK
   nsIFrame* thumbFrame = mFrames.FirstChild();
   if (thumbFrame) {

layout/xul/nsSliderFrame.h

@@ -195,6 +195,10 @@ private:
   // causing the scroll position to jump.
   bool mScrollingWithAPZ;
 
+  // true if displayport suppression is active, for more performant
+  // scrollbar-dragging behaviour.
+  bool mSuppressionActive;
+
   static bool gMiddlePref;
   static int32_t gSnapMultiplier;
 }; // class nsSliderFrame