Add Vector2d classes that represent offsets, instead of using Point.

chrome/browser/ui/gtk/tabs/dragged_tab_controller_gtk.cc

Index: chrome/browser/ui/gtk/tabs/dragged_tab_controller_gtk.cc
diff --git a/chrome/browser/ui/gtk/tabs/dragged_tab_controller_gtk.cc b/chrome/browser/ui/gtk/tabs/dragged_tab_controller_gtk.cc
index bfb1a1077c92547e238b5ebe0650344dd1b2c3cf..c08be1f0a0c70fc4c3de982cd0e7cbf0795d1958 100644
--- a/chrome/browser/ui/gtk/tabs/dragged_tab_controller_gtk.cc
+++ b/chrome/browser/ui/gtk/tabs/dragged_tab_controller_gtk.cc
@@ -507,7 +507,9 @@ gfx::Point DraggedTabControllerGtk::ConvertScreenPointToTabStripPoint(
     TabStripGtk* tabstrip, const gfx::Point& screen_point) {
   gfx::Point tabstrip_screen_point =
       ui::GetWidgetScreenPosition(tabstrip->tabstrip_.get());
-  return screen_point.Subtract(tabstrip_screen_point);
+  gfx::Vector2d tabstrip_offset =

[sky, 2012/10/26 21:37:50]

This results in a lot harder to read code.

[Peter Kasting, 2012/10/26 21:50:12]

I agree, but not because of Vector2d, just because of clumsy conversion.  IMO
this should have been written as:

  gfx::Point tabstrip_screen_point(
      ui::GetWidgetScreenPosition(tabstrip->tabstrip_.get()));
  return screen_point - tabstrip_screen_point.DistanceFromOrigin();

(Optionally, one could inline everything into the return statement.)

This becomes even simpler if we change GetWidgetScreenPosition() to
GetWidgetScreenOffset() and have it return a Vector2d -- which, I suspect, is
what every caller is really going to want.

[danakj, 2012/10/26 21:59:43]

I'll look into that, thanks.

There's probably a few clumsy conversions in here.. I tried to be
careful/meticulous but clearly it can be improved.

[danakj, 2012/10/26 23:30:34]

This certainly does clean up things, such as ConvertWidgetPointToScreen in
gtk_util.cc.

The one place that actually wants a point, is duplicating code from
GetWidgetScreenRect, so switched it to that.

+      screen_point.DistanceFrom(tabstrip_screen_point);
+  return gfx::PointAtDistanceFromOrigin(tabstrip_offset);
 }
 
 gfx::Rect DraggedTabControllerGtk::GetDraggedViewTabStripBounds(
@@ -818,7 +820,7 @@ gfx::Rect DraggedTabControllerGtk::GetAnimateBounds() {
   GtkWidget* widget = tab->widget();
   GtkWidget* parent = gtk_widget_get_parent(widget);
   gfx::Point point = ui::GetWidgetScreenPosition(parent);
-  bounds.Offset(point);
+  bounds.Offset(point.DistanceFromOrigin());
 
   return gfx::Rect(bounds.x(), bounds.y(),
                    dragged_view_->GetTotalWidthInTabStrip(), bounds.height());