MacViews: Overlay Scrollbars with Show/Hide Animations

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"
+#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 {
+
+// The transparent scrollbar which overlays its contents.

[tapted, 2016/02/16 06:47:58]

nit: mention Mac?

[spqchan, 2016/02/16 23:18:18]

Done.

+class VIEWS_EXPORT CocoaScrollBar : public BaseScrollBar,
+                                    public ViewsScrollbarBridgeDelegate {
+ public:
+  explicit CocoaScrollBar(bool horizontal);
+  ~CocoaScrollBar() override;
+
+  // Called by CocoaScrollBarThumb when the mouse enters or exits the view.
+  void OnMouseEnteredScrollbarThumb(const ui::MouseEvent& event);
+  void OnMouseExitedScrollbarThumb(const ui::MouseEvent& event);
+
+  // ScrollDelegate override

[tapted, 2016/02/16 06:47:58]

nit: `// ScrollDelegate:`

(i.e. since we've been putting `override` on all the method names, saying more
than this in the comment seems redundant, and this is how views OWNERS have
suggested it for new code (unless it's inconsistent with surrounding code in the
same file)

[spqchan, 2016/02/16 23:18:18]

Done.

+  bool OnScroll(float dx, float dy) override;
+
+  // ViewsScrollbarBridgeDelegate override

[tapted, 2016/02/16 06:47:58]

// ViewsScrollbarBridgeDelegate:

[spqchan, 2016/02/16 23:18:18]

Done.

+  void OnScrollerStyleChanged() override;
+
+ protected:
+  // BaseScrollBar override:

[tapted, 2016/02/16 06:47:58]

// BaseScrollBar:

[spqchan, 2016/02/16 23:18:18]

Done.

+  gfx::Rect GetTrackBounds() const override;
+
+  // ScrollBar overrides:

[tapted, 2016/02/16 06:47:58]

// ScrollBar:

[spqchan, 2016/02/16 23:18:18]

Done.

+  int GetLayoutSize() const override;
+  int GetContentOverlapSize() const override;
+
+  // View overrides:

[tapted, 2016/02/16 06:47:58]

// View:

[spqchan, 2016/02/16 23:18:18]

Done.

+  gfx::Size GetPreferredSize() const override;
+  void Layout() override;
+  void OnPaint(gfx::Canvas* canvas) override;
+
+ private:
+  // Methods to change the visibility of the scrollbar.
+  void ShowScrollbar();
+  void HideScrollbar();
+
+  // Resets hide_scrollbar_timer_ if the timer is running. Otherwise, this
+  // method will just start the timer.
+  void ResetTimer();
+
+  // Scroller style the scrollbar is using.
+  NSScrollerStyle scroller_style_;
+
+  // Timer that will start the scrollbar's hiding animation when it reaches 0.
+  base::OneShotTimer hide_scrollbar_timer_;
+
+  // True when the scrolltrack should be drawn.
+  bool has_scrolltrack_;
+
+  // True if the scrollbar is in its hover state.
+  bool is_hovering_;
+
+  // The bridge for NSScroller.
+  base::scoped_nsobject<ViewsScrollbarBridge> bridge_;
+  DISALLOW_COPY_AND_ASSIGN(CocoaScrollBar);

[tapted, 2016/02/16 06:47:58]

nit: blank line before

[spqchan, 2016/02/16 23:18:18]

Done.

+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_CONTROLS_SCROLLBAR_COCOA_SCROLL_BAR_H_