MacViews: Overlay Scrollbars with Show/Hide Animations

ui/views/controls/scroll_view.h

 // 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.
 
 #ifndef UI_VIEWS_CONTROLS_SCROLL_VIEW_H_
 #define UI_VIEWS_CONTROLS_SCROLL_VIEW_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
 #include "ui/views/controls/scrollbar/scroll_bar.h"
 
 namespace views {
 
 /////////////////////////////////////////////////////////////////////////////
 //
 // ScrollView class
 //
 // A ScrollView is used to make any View scrollable. The view is added to
 // a viewport which takes care of clipping.
@@ skipping 38 matching lines @@
 
   // Returns whether or not the ScrollView is bounded (as set by ClipHeightTo).
   bool is_bounded() const { return max_height_ >= 0 && min_height_ >= 0; }
 
   // Retrieves the width/height of scrollbars. These return 0 if the scrollbar
   // has not yet been created.
   int GetScrollBarWidth() const;
   int GetScrollBarHeight() const;
 
   // Returns the horizontal/vertical scrollbar. This may return NULL.
-  const ScrollBar* horizontal_scroll_bar() const { return horiz_sb_; }
+  const ScrollBar* horizontal_scroll_bar() const { return horiz_sb_.get(); }
   const ScrollBar* vertical_scroll_bar() const { return vert_sb_; }
 
   // Customize the scrollbar design. ScrollView takes the ownership of the
   // specified ScrollBar. |horiz_sb| and |vert_sb| cannot be NULL.
   void SetHorizontalScrollBar(ScrollBar* horiz_sb);
   void SetVerticalScrollBar(ScrollBar* vert_sb);
 
   // View overrides:
   gfx::Size GetPreferredSize() const override;
   int GetHeightForWidth(int width) const override;
@@ skipping 43 matching lines @@
   // |contents_viewport_|.
   View* contents_;
   View* contents_viewport_;
 
   // The current header and its viewport. |header_| is contained in
   // |header_viewport_|.
   View* header_;
   View* header_viewport_;
 
   // Horizontal scrollbar.
-  ScrollBar* horiz_sb_;
+  scoped_ptr<ScrollBar> horiz_sb_;

[tapted, 2016/02/09 23:51:48]

I don't immediately grok this bit (I may just need to look closer), or why the
same isn't done for vert_sb_;  - it might just need a comment to clarify.

I have a vague memory of looking at this in the past and wondering why these
were not scoped_ptr, and then realising why. I think it was because ScrollView
needed to `delete horiz_sb_;` to remove the view from the view hierarchy, but it
was invalid for the the ~ScrollView() destructor to do that because the
super-views::View (which *actually* owns the view) may have already done the
`delete horiz_sb_`, and left ScrollView with an invalid pointer.

[spqchan, 2016/02/10 00:35:16]

Sorry, this wasn't supposed to be here. This is actually test code (I was
changing horiz_sb to the NativeCocoaScrollbar so I could compare it with
vert_sb).
I was considering on replacing both of them with scoped_ptrs in the future, but
it looks like I should leave them as just pointers. Anyway, I just removed it

 
   // Vertical scrollbar.
   ScrollBar* vert_sb_;
 
   // Corner view.
   View* corner_view_;
 
   // The min and max height for the bounded scroll view. These are negative
   // values if the view is not bounded.
   int min_height_;
@@ skipping 72 matching lines @@
  private:
   int top_margin_;
   int row_height_;
 
   DISALLOW_COPY_AND_ASSIGN(FixedRowHeightScrollHelper);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_SCROLL_VIEW_H_