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
new file mode 100644
index 0000000000000000000000000000000000000000..691d774d4e816b6575a0599cb5bec8c98e125bce
--- /dev/null
+++ b/ui/views/controls/scrollbar/native_cocoa_scroll_bar.h
@@ -0,0 +1,83 @@
+// 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, 2016/02/08 00:31:15]

nit: needs a comment

also I'm not sure about `Native` :). Usually that means we're using some native
drawing code, but we're actually emulating it. So perhaps `Emulated`? Or
something else - I'm not fully sold on Emulated either

Note there is http://crbug.com/93103 "Get rid of NativeScrollBar" (or, just
rename/merge it really)

[spqchan, 2016/02/09 21:21:25]

That's true, I'm not sure what the best name it is atm. Let's rename it after we
figure out what to do with NativeScrollBar

+    : public NativeScrollBarViews,
+      public ViewsScrollbarBridgeDelegate,
+      public gfx::AnimationDelegate {
+ public:
+  explicit NativeCocoaScrollBarViews(NativeScrollBar* native_scroll_bar);
+  ~NativeCocoaScrollBarViews() override;
+
+  // BaseScrollBar override
+  bool OnScroll(float dx, float dy) override;
+
+  ui::NativeTheme::OverlayParams GetOverlayParams() override;
+
+  // ViewsScrollbarBridgeDelegate override
+  void OnScrollerStyleChanged() override;
+
+  // Gets the scroller style from OSX and updates the scollbar if the style
+  // has changed or hasn't been initialized yet.
+  void UpdateScrollStyle();
+
+ private:
+  // gfx::AnimationDelegate overrides:
+  void AnimationProgressed(const gfx::Animation* animation) override;
+
+  void ShowScrollbar();
+  void HideScrollbar();
+
+  NSScrollerStyle scroller_style_;

[tapted, 2016/02/08 00:31:15]

needs an initializer, since UpdateScrollStyle checks the current value.
NSScrollerStyle is typedef NSInteger, so perhaps just initialize to `-1` to
force the setup the first time UpdateScrollStyle is called. Then you can
probably get rid of the separate |init_| data member. (But comment here like

// The current scroller style, or -1 before it is initialized.
NSScrollerStyle scroller_style_ = -1;


But! The initialization flow might really need to be tweaked a bit. E.g. it
should never animate. Perhaps the constructor should just call [bridge_
getPreferredScrollerStyle] and set properties appropriately without animating

[spqchan, 2016/02/09 21:21:25]

Hm, that is true. I can't set it to -1 since it's outside the enum range
However, I just ended up calling getPreferredScrollerStyle instead

+
+  // Hiding animation for the scrollbars.
+  gfx::LinearAnimation animation_;
+
+  // Timer that will start the scrollbar's hiding animation when it reaches 0.
+  base::OneShotTimer hide_scrollbar_timer_;
+
+  // The opacity of the scrollbar.
+  double scroller_opacity_;

[tapted, 2016/02/08 00:31:15]

This should probably be initialized too

[spqchan, 2016/02/09 21:21:25]

Done.

+
+  // The bridge for NSScroller.
+  base::scoped_nsobject<ViewsScrollbarBridge> bridge_;
+
+  // Set to true after the object is initialized.
+  bool init_;

[tapted, 2016/02/08 00:31:15]

(remove[ or initialize])

[spqchan, 2016/02/09 21:21:25]

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(NativeCocoaScrollBarViews);
+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_CONTROLS_SCROLLBAR_COCOA_SCROLL_BAR_H_