Bug 1349750 - Move the scroll track extents from AsyncDragMetrics to ScrollThumbData. r=kats

To conserve space in LayerAttributes, we only store the extents along the
relevant axis.

MozReview-Commit-ID: GAL8Oa2NOde

gfx/ipc/GfxMessageUtils.h

@@ -1305,7 +1305,6 @@ struct ParamTraits<mozilla::layers::AsyncDragMetrics>
     WriteParam(aMsg, aParam.mPresShellId);
     WriteParam(aMsg, aParam.mDragStartSequenceNumber);
     WriteParam(aMsg, aParam.mScrollbarDragOffset);
-    WriteParam(aMsg, aParam.mScrollTrack);
     WriteParam(aMsg, aParam.mDirection);
   }
 
@@ -1315,7 +1314,6 @@ struct ParamTraits<mozilla::layers::AsyncDragMetrics>
             ReadParam(aMsg, aIter, &aResult->mPresShellId) &&
             ReadParam(aMsg, aIter, &aResult->mDragStartSequenceNumber) &&
             ReadParam(aMsg, aIter, &aResult->mScrollbarDragOffset) &&
-            ReadParam(aMsg, aIter, &aResult->mScrollTrack) &&
             ReadParam(aMsg, aIter, &aResult->mDirection));
   }
 };

gfx/layers/LayerAttributes.h

@@ -27,11 +27,15 @@ struct ScrollThumbData {
   ScrollThumbData(ScrollDirection aDirection,
                   float aThumbRatio,
                   CSSCoord aThumbLength,
-                  bool aIsAsyncDraggable)
+                  bool aIsAsyncDraggable,
+                  CSSCoord aScrollTrackStart,
+                  CSSCoord aScrollTrackLength)
     : mDirection(aDirection)
     , mThumbRatio(aThumbRatio)
     , mThumbLength(aThumbLength)
     , mIsAsyncDraggable(aIsAsyncDraggable)
+    , mScrollTrackStart(aScrollTrackStart)
+    , mScrollTrackLength(aScrollTrackLength)
   {}
 
   ScrollDirection mDirection;
@@ -42,12 +46,16 @@ struct ScrollThumbData {
   CSSCoord mThumbLength;
   // Whether the scrollbar thumb can be dragged asynchronously.
   bool mIsAsyncDraggable;
+  CSSCoord mScrollTrackStart;
+  CSSCoord mScrollTrackLength;
 
   bool operator==(const ScrollThumbData& aOther) const {
     return mDirection == aOther.mDirection &&
            mThumbRatio == aOther.mThumbRatio &&
            mThumbLength == aOther.mThumbLength &&
-           mIsAsyncDraggable == aOther.mIsAsyncDraggable;
+           mIsAsyncDraggable == aOther.mIsAsyncDraggable &&
+           mScrollTrackStart == aOther.mScrollTrackStart &&
+           mScrollTrackLength == aOther.mScrollTrackLength;
   }
   bool operator!=(const ScrollThumbData& aOther) const {
     return !(*this == aOther);

gfx/layers/apz/src/AsyncDragMetrics.h

@@ -41,13 +41,11 @@ public:
                    uint32_t aPresShellId,
                    uint64_t aDragStartSequenceNumber,
                    CSSCoord aScrollbarDragOffset,
-                   const CSSRect& aScrollTrack,
                    DragDirection aDirection)
     : mViewId(aViewId)
     , mPresShellId(aPresShellId)
     , mDragStartSequenceNumber(aDragStartSequenceNumber)
     , mScrollbarDragOffset(aScrollbarDragOffset)
-    , mScrollTrack(aScrollTrack)
     , mDirection(aDirection)
   {}
 
@@ -55,7 +53,6 @@ public:
   uint32_t mPresShellId;
   uint64_t mDragStartSequenceNumber;
   CSSCoord mScrollbarDragOffset;
-  CSSRect mScrollTrack;
   DragDirection mDirection;
 };
 

gfx/layers/apz/src/AsyncPanZoomController.cpp

@@ -926,9 +926,9 @@ nsEventStatus AsyncPanZoomController::HandleDragEvent(const MouseInput& aEvent,
   CSSCoord mousePosition = GetAxisStart(aDragMetrics.mDirection, scrollbarPoint) -
                         aDragMetrics.mScrollbarDragOffset -
                         GetAxisStart(aDragMetrics.mDirection, cssCompositionBound) -
-                        GetAxisStart(aDragMetrics.mDirection, aDragMetrics.mScrollTrack);
+                        thumbData.mScrollTrackStart;
 
-  CSSCoord scrollMax = GetAxisLength(aDragMetrics.mDirection, aDragMetrics.mScrollTrack);
+  CSSCoord scrollMax = thumbData.mScrollTrackLength;
   scrollMax -= thumbData.mThumbLength;
 
   float scrollPercent = mousePosition / scrollMax;

layout/xul/nsSliderFrame.cpp

@@ -361,10 +361,10 @@ nsSliderFrame::BuildDisplayListForChildren(nsDisplayListBuilder*   aBuilder,
     thumb->GetXULMargin(m);
     thumbRect.Inflate(m);
 
-    nsRect crect;
+    nsRect sliderTrack;
-    GetXULClientRect(crect);
+    GetXULClientRect(sliderTrack);
 
-    if (crect.width < thumbRect.width || crect.height < thumbRect.height)
+    if (sliderTrack.width < thumbRect.width || sliderTrack.height < thumbRect.height)
       return;
 
     // If this scrollbar is the scrollbar of an actively scrolled scroll frame,
@@ -394,6 +394,21 @@ nsSliderFrame::BuildDisplayListForChildren(nsDisplayListBuilder*   aBuilder,
       nsIFrame* scrollbarBox = GetScrollbar();
       bool isAsyncDraggable = !UsesCustomScrollbarMediator(scrollbarBox);
 
+      nsPoint scrollPortOrigin;
+      if (nsIScrollableFrame* scrollFrame = do_QueryFrame(scrollbarBox->GetParent())) {
+        scrollPortOrigin = scrollFrame->GetScrollPortRect().TopLeft();
+      } else {
+        isAsyncDraggable = false;
+      }
+
+      // This rect is the range in which the scroll thumb can slide in.
+      sliderTrack = sliderTrack + GetRect().TopLeft() + scrollbarBox->GetPosition() -
+                    scrollPortOrigin;
+      CSSCoord sliderTrackStart = NSAppUnitsToFloatPixels(
+          isHorizontal ? sliderTrack.x : sliderTrack.y, appUnitsPerCss);
+      CSSCoord sliderTrackLength = NSAppUnitsToFloatPixels(
+          isHorizontal ? sliderTrack.width : sliderTrack.height, appUnitsPerCss);
+
       nsDisplayListBuilder::AutoContainerASRTracker contASRTracker(aBuilder);
       nsDisplayListCollection tempLists;
       nsBoxFrame::BuildDisplayListForChildren(aBuilder, aDirtyRect, tempLists);
@@ -418,7 +433,9 @@ nsSliderFrame::BuildDisplayListForChildren(nsDisplayListBuilder*   aBuilder,
                           ScrollThumbData{scrollDirection,
                                           GetThumbRatio(),
                                           thumbLength,
-                                          isAsyncDraggable}));
+                                          isAsyncDraggable,
+                                          sliderTrackStart,
+                                          sliderTrackLength}));
 
       return;
     }
@@ -1044,11 +1061,6 @@ nsSliderFrame::StartAPZDrag(WidgetGUIEvent* aEvent)
     return;
   }
 
-  nsIScrollableFrame* scrollFrameAsScrollable = do_QueryFrame(scrollFrame);
-  if (!scrollFrameAsScrollable) {
-    return;
-  }
-
   // APZ dragging requires the scrollbar to be layerized, which doesn't
   // happen for scroll info layers.
   if (ScrollFrameWillBuildScrollInfoLayer(scrollFrame)) {
@@ -1072,21 +1084,12 @@ nsSliderFrame::StartAPZDrag(WidgetGUIEvent* aEvent)
 
   nsCOMPtr<nsIContent> scrollbar = GetContentOfBox(scrollbarBox);
 
-  nsRect sliderTrack;
-  GetXULClientRect(sliderTrack);
-
-  // This rect is the range in which the scroll thumb can slide in.
-  sliderTrack = sliderTrack + GetRect().TopLeft() + scrollbarBox->GetPosition() -
-                scrollFrameAsScrollable->GetScrollPortRect().TopLeft();
-  CSSRect sliderTrackCSS = CSSRect::FromAppUnits(sliderTrack);
-
   nsIPresShell* shell = PresContext()->PresShell();
   uint64_t inputblockId = InputAPZContext::GetInputBlockId();
   uint32_t presShellId = shell->GetPresShellId();
   AsyncDragMetrics dragMetrics(scrollTargetId, presShellId, inputblockId,
                                NSAppUnitsToFloatPixels(mDragStart,
                                  float(AppUnitsPerCSSPixel())),
-                               sliderTrackCSS,
                                isHorizontal ? AsyncDragMetrics::HORIZONTAL :
                                               AsyncDragMetrics::VERTICAL);