MacViews: Overlay Scrollbars with Show/Hide Animations

ui/views/controls/scrollbar/base_scroll_bar.cc

 // Copyright (c) 2012 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.
 
 #include "ui/views/controls/scrollbar/base_scroll_bar.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/compiler_specific.h"
@@ skipping 110 matching lines @@
   if (old_state == CustomButton::STATE_PRESSED &&
       new_state == CustomButton::STATE_NORMAL &&
       GetThumbTrackState() == CustomButton::STATE_HOVERED) {
     SetThumbTrackState(CustomButton::STATE_NORMAL);
   }
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 // BaseScrollBar, View implementation:
 
+void BaseScrollBar::Layout() {

[tapted, 2016/02/22 04:42:15]

If we keep this here, the identical logic can be removed from
overlay_scroll_bar.cc

However, I just tried it out, and I think this can be simplified to just
`GetThumb()->SetBoundsRect(GetTrackBounds())` (in CocoaScrollBar)

That's what NativeScrollBarViews does, but since it's just one line, I think
it's fine to just put it in CocoaScrollBar, and remove the default-provided
implementation (make BaseScrollBar::Layout() pure virtual again). (I think this
will be more appealing to OWNERS too, but beforehand it was too much duplicated
logic).

[spqchan, 2016/02/22 19:01:37]

Done.

+  // Provide a default implementation that sets the thumb's bounds in the
+  // scrollbar.
+  gfx::Rect thumb_bounds = GetTrackBounds();
+  if (IsHorizontal()) {
+    thumb_bounds.set_x(thumb_->x());
+    thumb_bounds.set_width(thumb_->width());
+  } else {
+    thumb_bounds.set_y(thumb_->y());
+    thumb_bounds.set_height(thumb_->height());
+  }
+  thumb_->SetBoundsRect(thumb_bounds);
+}
+
 bool BaseScrollBar::OnMousePressed(const ui::MouseEvent& event) {
   if (event.IsOnlyLeftMouseButton())
     ProcessPressEvent(event);
   return true;
 }
 
 void BaseScrollBar::OnMouseReleased(const ui::MouseEvent& event) {
   SetState(HitTestPoint(event.location()) ?
            CustomButton::STATE_HOVERED : CustomButton::STATE_NORMAL);
 }
@@ skipping 367 matching lines @@
     thumb_position = thumb_position - (thumb_->GetSize() / 2);
   return (thumb_position * contents_size_) / GetTrackSize();
 }
 
 void BaseScrollBar::SetThumbTrackState(CustomButton::ButtonState state) {
   thumb_track_state_ = state;
   SchedulePaint();
 }
 
 }  // namespace views