Refactor intra-strip panel drags by introducing PanelDragController.

chrome/browser/ui/panels/detached_panel_strip.h

Index: chrome/browser/ui/panels/detached_panel_strip.h
diff --git a/chrome/browser/ui/panels/detached_panel_strip.h b/chrome/browser/ui/panels/detached_panel_strip.h
index 868093bd59a237e6e9b9179bcf6b384d90b86932..32569cc8bfa4ac4a2d5705af2fac5c6eb1765e47 100644
--- a/chrome/browser/ui/panels/detached_panel_strip.h
+++ b/chrome/browser/ui/panels/detached_panel_strip.h
@@ -10,6 +10,7 @@
 #include "base/basictypes.h"
 #include "chrome/browser/ui/panels/panel.h"
 #include "chrome/browser/ui/panels/panel_strip.h"
+#include "ui/gfx/point.h"
 #include "ui/gfx/rect.h"
 
 class Browser;
@@ -36,6 +37,10 @@ class DetachedPanelStrip : public PanelStrip {
   virtual void ActivatePanel(Panel* panel) OVERRIDE;
   virtual void MinimizePanel(Panel* panel) OVERRIDE;
   virtual void RestorePanel(Panel* panel) OVERRIDE;
+  virtual bool CanDragPanel(Panel* panel) const OVERRIDE;
+  virtual void StartDraggingPanel(Panel* panel) OVERRIDE;
+  virtual void DragPanel(int delta_x, int delta_y) OVERRIDE;
+  virtual void EndDraggingPanel(bool cancelled) OVERRIDE;
 
   int num_panels() const { return panels_.size(); }
   const Panels& panels() const { return panels_; }
@@ -49,6 +54,13 @@ class DetachedPanelStrip : public PanelStrip {
   // Collection of all panels.
   Panels panels_;
 
+  // Panel being dragged.
+  Panel* dragging_panel_;

[jennb, 2012/02/16 22:31:00]

This is already tracked in drag controller. Do we really need to track it again
in both this strip and the docked strip?

[jianli, 2012/02/16 23:05:52]

They're served for different purpose. PanelDragController::dragging_panel_
represents the panel being dragged, no matter whether it is intra-strip or
inter-strip. It is always valid when there is a drag.
PanelStrip::dragging_panel_ denotes the panel being dragged inside this strip.
It will only be valid when the drag enters this strip.

Though we could still try to use draagging_panel_ from drag controller, but it
would require checking if the strip that the dragging is on is this strip, which
is a bit complicated. I rather have each strip know about all the info to
process intra-strip drags.

+
+  // Original position of the panel being dragged. This is used to get back to
+  // the original position when we cancel the dragging.
+  gfx::Point dragging_panel_original_position_;

[jennb, 2012/02/16 22:31:00]

What is position? the x,y coordinates of the panel's bounds? Would it make sense
to simply store original bounds?

[jianli, 2012/02/16 23:05:52]

The origin (x, y coordinates) of the panel's bounds. We only intend to use the
origin. So I rather not to save extra info that was not used.

+
   DISALLOW_COPY_AND_ASSIGN(DetachedPanelStrip);
 };