MacViews: Overlay Scrollbars with Show/Hide Animations

ui/views/controls/scrollbar/native_cocoa_scroll_bar.h

Index: ui/views/controls/scrollbar/native_cocoa_scroll_bar.h
diff --git a/ui/views/controls/scrollbar/native_cocoa_scroll_bar.h b/ui/views/controls/scrollbar/native_cocoa_scroll_bar.h
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+++ b/ui/views/controls/scrollbar/native_cocoa_scroll_bar.h
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+// 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_NATIVE_COCOA_SCROLL_BAR_H_
+#define UI_VIEWS_CONTROLS_SCROLLBAR_NATIVE_COCOA_SCROLL_BAR_H_
+
+#include "base/macros.h"
+#import "base/mac/scoped_nsobject.h"
+#include "ui/gfx/animation/linear_animation.h"
+#import "ui/views/cocoa/views_scrollbar_bridge.h"
+#include "ui/views/controls/scrollbar/base_scroll_bar.h"
+#include "ui/views/controls/scrollbar/native_scroll_bar.h"
+#include "ui/views/controls/scrollbar/native_scroll_bar_views.h"
+#include "ui/views/views_export.h"
+
+@class ViewsScrollbarBridge;
+
+namespace views {
+
+// The transparent scrollbar which overlays its contents.
+class VIEWS_EXPORT NativeCocoaScrollBar : public NativeScrollBar {
+ public:
+  explicit NativeCocoaScrollBar(bool horizontal);
+  ~NativeCocoaScrollBar() override;
+
+ protected:
+  NativeScrollBarWrapper* CreateWrapper() override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(NativeCocoaScrollBar);
+};
+
+class VIEWS_EXPORT NativeCocoaScrollBarViews
+    : public NativeScrollBarViews,
+      public ViewsScrollbarBridgeDelegate {
+ public:
+  explicit NativeCocoaScrollBarViews(NativeScrollBar* native_scroll_bar);
+  ~NativeCocoaScrollBarViews() override;
+
+  // BaseScrollBar override
+  bool OnScroll(float dx, float dy) override;
+
+  // ViewsScrollbarBridgeDelegate override
+  void OnScrollerStyleChanged() override;
+
+ private:
+  void ShowScrollbar();
+  void HideScrollbar();
+
+  NSScrollerStyle scroller_style_;
+
+  // Timer that will start the scrollbar's hiding animation when it reaches 0.
+  base::OneShotTimer hide_scrollbar_timer_;
+
+  // The bridge for NSScroller.
+  base::scoped_nsobject<ViewsScrollbarBridge> bridge_;
+
+  DISALLOW_COPY_AND_ASSIGN(NativeCocoaScrollBarViews);
+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_CONTROLS_SCROLLBAR_COCOA_SCROLL_BAR_H_