MacViews: Reveal scrollbars when resting on the trackpad.

ui/views/controls/scrollbar/cocoa_scroll_bar.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_VIEWS_CONTROLS_SCROLLBAR_COCOA_SCROLL_BAR_H_
 #define UI_VIEWS_CONTROLS_SCROLLBAR_COCOA_SCROLL_BAR_H_
 
 #include "base/macros.h"
 #import "base/mac/scoped_nsobject.h"
 #include "ui/compositor/layer_animation_observer.h"
 #include "ui/gfx/animation/slide_animation.h"
 #import "ui/views/cocoa/views_scrollbar_bridge.h"
 #include "ui/views/controls/scrollbar/base_scroll_bar.h"
 #include "ui/views/views_export.h"
 
 namespace views {
 
 class CocoaScrollBarThumb;
 
 // The transparent scrollbar for Mac which overlays its contents.
 class VIEWS_EXPORT CocoaScrollBar : public BaseScrollBar,
                                     public ViewsScrollbarBridgeDelegate,
                                     public ui::ImplicitAnimationObserver,
                                     public gfx::AnimationDelegate {
  public:
   explicit CocoaScrollBar(bool horizontal);
   ~CocoaScrollBar() override;
 
-  // BaseScrollBar:
-  void ScrollToPosition(int position) override;
+  // ScrollBar:
+  void Update(int viewport_size,
+              int content_size,
+              int contents_scroll_offset) override;
+  void ObserveScrollEvent(const ui::ScrollEvent& event) override;
 
   // ViewsScrollbarBridgeDelegate:
   void OnScrollerStyleChanged() override;
 
   // View:
   bool OnMousePressed(const ui::MouseEvent& event) override;
   void OnMouseReleased(const ui::MouseEvent& event) override;
   void OnMouseEntered(const ui::MouseEvent& event) override;
   void OnMouseExited(const ui::MouseEvent& event) override;
 
@@ skipping 17 matching lines @@
   // ScrollBar:
   int GetLayoutSize() const override;
   int GetContentOverlapSize() const override;
 
   // View:
   void Layout() override;
   gfx::Size GetPreferredSize() const override;
   void OnPaint(gfx::Canvas* canvas) override;
 
  private:
+  friend class BaseScrollBar;  // For BaseScrollBar::GetHideTimerForTest().
+
   // Methods to change the visibility of the scrollbar.
   void ShowScrollbar();
   void HideScrollbar();
 
   // Returns true if the scrollbar is in a hover or pressed state.
   bool IsHoverOrPressedState() const;
 
   // Updates the thickness of the scrollbar according to the current state of
   // the expand animation.
   void UpdateScrollbarThickness();
@@ skipping 15 matching lines @@
   NSScrollerStyle scroller_style_;
 
   // Timer that will start the scrollbar's hiding animation when it reaches 0.
   base::Timer hide_scrollbar_timer_;
 
   // Slide animation that animates the thickness of an overlay scrollbar.
   // The animation expands the scrollbar as the showing animation and shrinks
   // the scrollbar as the hiding animation.
   gfx::SlideAnimation thickness_animation_;
 
+  // The scroll offset from the last adjustment to the scroll bar.

[spqchan, 2016/11/14 23:27:58]

"scroll bar" -> "scrollbar

[tapted, 2016/11/15 12:22:23]

Done.

+  int last_contents_scroll_offset_;
+
   // True when the scrollbar is expanded.
   bool is_expanded_;
 
   // True when the scrolltrack should be drawn.
   bool has_scrolltrack_;
 
   // True when the scrollbar has started dragging since it was last shown.
   // This is set to false when we begin to hide the scrollbar.
   bool did_start_dragging_;
 
   // The bridge for NSScroller.
   base::scoped_nsobject<ViewsScrollbarBridge> bridge_;
 
   DISALLOW_COPY_AND_ASSIGN(CocoaScrollBar);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_SCROLLBAR_COCOA_SCROLL_BAR_H_