Implement overlay scrollbar fade out for non-composited scrollers.

third_party/WebKit/Source/platform/scroll/ScrollableArea.h

 /*
  * Copyright (C) 2008, 2011 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 89 matching lines @@
   // Returns a rect, in the space of the area's backing graphics layer, that
   // contains the visual region of all scrollbar parts.
   virtual LayoutRect visualRectForScrollbarParts() const = 0;
 
   static bool scrollBehaviorFromString(const String&, ScrollBehavior&);
 
   void contentAreaWillPaint() const;
   void mouseEnteredContentArea() const;
   void mouseExitedContentArea() const;
   void mouseMovedInContentArea() const;
-  void mouseEnteredScrollbar(Scrollbar&) const;
-  void mouseExitedScrollbar(Scrollbar&) const;
+  void mouseEnteredScrollbar(Scrollbar&);
+  void mouseExitedScrollbar(Scrollbar&);
+  void mouseCapturedScrollbar();
+  void mouseReleasedScrollbar();
   void contentAreaDidShow() const;
   void contentAreaDidHide() const;
 
   void finishCurrentScrollAnimations() const;
 
   virtual void didAddScrollbar(Scrollbar&, ScrollbarOrientation);
   virtual void willRemoveScrollbar(Scrollbar&, ScrollbarOrientation);
 
   virtual void contentsResized();
 
@@ skipping 98 matching lines @@
 
   virtual IntRect visibleContentRect(
       IncludeScrollbarsInRect = ExcludeScrollbars) const;
   virtual int visibleHeight() const { return visibleContentRect().height(); }
   virtual int visibleWidth() const { return visibleContentRect().width(); }
   virtual IntSize contentsSize() const = 0;
   virtual IntPoint lastKnownMousePosition() const { return IntPoint(); }
 
   virtual bool shouldSuspendScrollAnimations() const { return true; }
   virtual void scrollbarStyleChanged() {}
-  virtual void scrollbarVisibilityChanged() {}
   virtual bool scrollbarsCanBeActive() const = 0;
 
   // Returns the bounding box of this scrollable area, in the coordinate system
   // of the enclosing scroll view.
   virtual IntRect scrollableAreaBoundingBox() const = 0;
 
   virtual bool scrollAnimatorEnabled() const { return false; }
 
   // NOTE: Only called from Internals for testing.
   void updateScrollOffsetFromInternals(const IntSize&);
 
   IntSize clampScrollOffset(const IntSize&) const;
   ScrollOffset clampScrollOffset(const ScrollOffset&) const;
 
   // Let subclasses provide a way of asking for and servicing scroll
   // animations.
   virtual bool scheduleAnimation();
   virtual void serviceScrollAnimations(double monotonicTime);
   virtual void updateCompositorScrollAnimations();
   virtual void registerForAnimation() {}
   virtual void deregisterForAnimation() {}
 
   virtual bool usesCompositedScrolling() const { return false; }
   virtual bool shouldScrollOnMainThread() const;
 
   // Overlay scrollbars can "fade-out" when inactive.
   virtual bool scrollbarsHidden() const;
   virtual void setScrollbarsHidden(bool);
-  virtual void didChangeScrollbarsHidden(){};
 
   // Returns true if the GraphicsLayer tree needs to be rebuilt.
   virtual bool updateAfterCompositingChange() { return false; }
 
   virtual bool userInputScrollable(ScrollbarOrientation) const = 0;
   virtual bool shouldPlaceVerticalScrollbarOnLeft() const = 0;
 
   // Convenience functions
   float scrollOffset(ScrollbarOrientation orientation) {
     return orientation == HorizontalScrollbar ? scrollOffsetInt().width()
@@ skipping 70 matching lines @@
   virtual bool isRootFrameViewport() const { return false; }
 
   // Returns true if the scroller adjusts the scroll offset to compensate
   // for layout movements (bit.ly/scroll-anchoring).
   virtual bool shouldPerformScrollAnchoring() const { return false; }
 
   // Need to promptly let go of owned animator objects.
   EAGERLY_FINALIZE();
   DECLARE_VIRTUAL_TRACE();
 
-  virtual void clearScrollAnimators();
+  virtual void clearScrollableArea();
 
   virtual ScrollAnchor* scrollAnchor() { return nullptr; }
 
+  void fadeOverlayScrollbarsTimerFired(TimerBase*);

[skobes, 2016/11/02 21:02:43]

Can this be private?

+
  protected:
   ScrollableArea();
 
   ScrollbarOrientation scrollbarOrientationFromDirection(
       ScrollDirectionPhysical) const;
   float scrollStep(ScrollGranularity, ScrollbarOrientation) const;
 
   void setScrollOrigin(const IntPoint&);
   void resetScrollOriginChanged() { m_scrollOriginChanged = false; }
 
   // Needed to let the animators call scrollOffsetChanged.
   friend class ScrollAnimatorCompositorCoordinator;
   void scrollOffsetChanged(const ScrollOffset&, ScrollType);
 
   bool horizontalScrollbarNeedsPaintInvalidation() const {
     return m_horizontalScrollbarNeedsPaintInvalidation;
   }
   bool verticalScrollbarNeedsPaintInvalidation() const {
     return m_verticalScrollbarNeedsPaintInvalidation;
   }
   bool scrollCornerNeedsPaintInvalidation() const {
     return m_scrollCornerNeedsPaintInvalidation;
   }
   void clearNeedsPaintInvalidationForScrollControls() {
     m_horizontalScrollbarNeedsPaintInvalidation = false;
     m_verticalScrollbarNeedsPaintInvalidation = false;
     m_scrollCornerNeedsPaintInvalidation = false;
   }
+  void showOverlayScrollbars();
+  virtual void scrollbarVisibilityChanged() {}
 
  private:
   void programmaticScrollHelper(const ScrollOffset&, ScrollBehavior);
   void userScrollHelper(const ScrollOffset&, ScrollBehavior);
 
   // This function should be overriden by subclasses to perform the actual
   // scroll of the content.
   virtual void updateScrollOffset(const ScrollOffset&, ScrollType) = 0;
 
   virtual int lineStep(ScrollbarOrientation) const;
   virtual int pageStep(ScrollbarOrientation) const;
   virtual int documentStep(ScrollbarOrientation) const;
   virtual float pixelStep(ScrollbarOrientation) const;
 
   mutable Member<ScrollAnimatorBase> m_scrollAnimator;
   mutable Member<ProgrammaticScrollAnimator> m_programmaticScrollAnimator;
 
+  std::unique_ptr<Timer<ScrollableArea>> m_fadeOverlayScrollbarsTimer;
+
   unsigned m_scrollbarOverlayColorTheme : 2;
 
   unsigned m_scrollOriginChanged : 1;
 
   unsigned m_horizontalScrollbarNeedsPaintInvalidation : 1;
   unsigned m_verticalScrollbarNeedsPaintInvalidation : 1;
   unsigned m_scrollCornerNeedsPaintInvalidation : 1;
   unsigned m_scrollbarsHidden : 1;
+  unsigned m_scrollbarCaptured : 1;
 
   // There are 6 possible combinations of writing mode and direction. Scroll
   // origin will be non-zero in the x or y axis if there is any reversed
   // direction or writing-mode. The combinations are:
   // writing-mode / direction     scrollOrigin.x() set    scrollOrigin.y() set
   // horizontal-tb / ltr          NO                      NO
   // horizontal-tb / rtl          YES                     NO
   // vertical-lr / ltr            NO                      NO
   // vertical-lr / rtl            NO                      YES
   // vertical-rl / ltr            YES                     NO
   // vertical-rl / rtl            YES                     YES
   IntPoint m_scrollOrigin;
 };
 
 }  // namespace blink
 
 #endif  // ScrollableArea_h