MacViews: Overlay Scrollbars with Show/Hide Animations

ui/views/controls/scrollbar/native_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_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

[tapted, 2016/02/11 08:46:17]

I think this should be

NativeScrollBarViewsMac

it should have a brief comment to describing what behaviours its responsible for

[spqchan, 2016/02/13 01:39:23]

I just switched back to CocoaScrollBar, do you think that name is alright?
If not, I can change it to NativeScrollBarViewsMac

+    : public NativeScrollBarViews,

[tapted, 2016/02/11 08:46:17]

We should override NativeScrollBarViews::OnPaint() so that the track isn't
painted for the overlay style -- that should be straightforward (I think we just
do nothing or call NativeScrollBarViews::OnPaint()).

[spqchan, 2016/02/13 01:39:23]

Did it for CocoaScrollBar.

+      public ViewsScrollbarBridgeDelegate {
+ public:
+  explicit NativeCocoaScrollBarViews(NativeScrollBar* native_scroll_bar);
+  ~NativeCocoaScrollBarViews() override;
+
+  // BaseScrollBar override

[tapted, 2016/02/11 08:46:17]

nit: Lately views OWNERS have been asking me to go with just

  // BaseScrollBar:

for these (I guess `override[s]` is kinda redundant now it's on every method and
part of the C++11 language

[spqchan, 2016/02/13 01:39:23]

Done.

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

[tapted, 2016/02/11 08:46:17]

Hm... how do we fix the layout so that the content renders underneath in proper
overlay style? It might be really simple... I tried borrowing some ideas from
OverlayScrollBar, like just overriding,

  // ScrollBar:
  int GetLayoutSize() const override;
  int GetContentOverlapSize() const override;

to just return 0 for layoutsize and NativeScrollBarViews::GetLayoutSize() for
GetContentOverlapSize(). But that didn't seem to be enough :/

[spqchan, 2016/02/13 01:39:23]

I used return 0 for GetLayoutSize()
I used the scrollbar width instead (pretty much the same thing as
GetLayoutSize()) and it looks like it's turning out okay.

There's a corner issue right now that I'll have to investigate though.

+  // 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_