MacViews: Overlay Scrollbars with Show/Hide Animations

ui/views/controls/scroll_view.h

Index: ui/views/controls/scroll_view.h
diff --git a/ui/views/controls/scroll_view.h b/ui/views/controls/scroll_view.h
index da384801d9682208c19ae558986b06fdb3bbece9..798ea002aaa54f6571af1665ea84d733c8acaf69 100644
--- a/ui/views/controls/scroll_view.h
+++ b/ui/views/controls/scroll_view.h
@@ -10,6 +10,7 @@
 #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 {
@@ -68,7 +69,7 @@ class VIEWS_EXPORT ScrollView : public View, public ScrollBarController {
   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
@@ -132,7 +133,7 @@ class VIEWS_EXPORT ScrollView : public View, public ScrollBarController {
   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_;