MacViews: Overlay Scrollbars with Show/Hide Animations

ui/views/controls/scroll_view.cc

Index: ui/views/controls/scroll_view.cc
diff --git a/ui/views/controls/scroll_view.cc b/ui/views/controls/scroll_view.cc
index 6902a8a346086f5c5bb89afbf9dfb658b1755b76..a3e1e9787a2ae32b3118c2d0ed9837d808f94d25 100644
--- a/ui/views/controls/scroll_view.cc
+++ b/ui/views/controls/scroll_view.cc
@@ -10,7 +10,7 @@
 #include "ui/gfx/canvas.h"
 #include "ui/native_theme/native_theme.h"
 #include "ui/views/border.h"
-#include "ui/views/controls/scrollbar/native_scroll_bar.h"
+#include "ui/views/style/platform_style.h"
 #include "ui/views/widget/root_view.h"
 
 namespace views {
@@ -124,8 +124,8 @@ ScrollView::ScrollView()
       contents_viewport_(new Viewport()),
       header_(NULL),
       header_viewport_(new Viewport()),
-      horiz_sb_(new NativeScrollBar(true)),
-      vert_sb_(new NativeScrollBar(false)),
+      horiz_sb_(PlatformStyle::CreateScrollBar(true).release()),
+      vert_sb_(PlatformStyle::CreateScrollBar(false).release()),

[Avi (use Gerrit), 2016/02/22 19:37:08]

o_O

Make horiz_sb_ and vert_sb_ into scoped_ptrs in a prep CL.

[spqchan, 2016/02/22 20:49:25]

What do you mean by a prep CL?

[Avi (use Gerrit), 2016/02/22 20:54:15]

I meant to make a new CL that makes horiz_sb_ and vert_sb_ into scoped_ptrs and
land that first, rebasing this on top of that one. Or alternatively, land this
as-is, but fix it in a follow-up.

If horiz_sb_ and vert_sb_ are owned, we should indicate it, not drop the
ownership here.

[tapted, 2016/02/22 22:22:23]

I think the reason for this is that horiz_sb_ and vert_sb_ can be owned either
by this class, or by "the view hierarchy" (i.e. the children_ vector in
views::View). Calling View::AddChildView(horiz_sb_) is always a transfer of
ownership, but since that's only "maybe" called in the lifetime of ScrollView,
ScrollView still needs a handle on the view so that it can delete it -- the
views::View destructor always first removes itself from any view hierarchy so
`delete horiz_sb_` in the ScrollView destructor will either remove itself from
the view hierarchy and delete the view, or just delete the view, depending on
what happened.


A scoped_ptr might still work for this, but `AddChildView(horiz_sb_.get())`
could be misleading, since there becomes effectively two non-weak owners of the
object.

       corner_view_(new ScrollCornerView()),
       min_height_(-1),
       max_height_(-1),
@@ -300,11 +300,15 @@ void ScrollView::Layout() {
     should_layout_contents = true;
   }
 
+  int height_offset = horiz_sb_required ?
+      horiz_sb_->GetContentOverlapSize() : 0;
+  int width_offset = vert_sb_required ?
+      vert_sb_->GetContentOverlapSize() : 0;
+
   if (horiz_sb_required) {
-    int height_offset = horiz_sb_->GetContentOverlapSize();
     horiz_sb_->SetBounds(contents_x,
                          viewport_bounds.bottom() - height_offset,
-                         viewport_bounds.right() - contents_x,
+                         viewport_bounds.right() - contents_x - width_offset,
                          horiz_sb_height + height_offset);
   }
   if (vert_sb_required) {
@@ -312,7 +316,7 @@ void ScrollView::Layout() {
     vert_sb_->SetBounds(viewport_bounds.right() - width_offset,
                         contents_y,
                         vert_sb_width + width_offset,
-                        viewport_bounds.bottom() - contents_y);
+                        viewport_bounds.bottom() - contents_y - height_offset);
   }
   if (corner_view_required) {
     // Show the resize corner.