Support detaching/attaching panels via inter-strip drags.

chrome/browser/ui/panels/panel_strip.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 CHROME_BROWSER_UI_PANELS_PANEL_STRIP_H_
 #define CHROME_BROWSER_UI_PANELS_PANEL_STRIP_H_
 #pragma once
 
+#include "ui/gfx/point.h"
 #include "ui/gfx/rect.h"
 
 class Panel;
 
 // Common base class for a collection of panels. Subclasses manage
 // various layouts for displaying panels in the collection.
 class PanelStrip {
  public:
   // Types of layout for the panel collections.
   enum Type {
     DETACHED,  // free-floating panels
     DOCKED,    // panels are 'docked' along the window's edge
     IN_OVERFLOW,  // panels that cannot fit in the 'docked' panels area
   };
 
   Type type() const { return type_; }
 
   // Sets the bounds of the panel strip.
   // |display_area| is in screen coordinates.
   virtual void SetDisplayArea(const gfx::Rect& display_area) = 0;
 
   // Updates the positioning of all panels in the collection, usually as
   // a result of removing or resizing a panel in collection.
   virtual void RefreshLayout() = 0;
 
   // Adds |panel| to the collection of panels.
   virtual void AddPanel(Panel* panel) = 0;
 
+  // Adds |panel| to the collection of panels and positions it at or close to
+  // |position| that is in screen coordinates. It is up to the strip itself to
+  // decide the final position that the panel can be.
+  virtual void AddPanelAtPosition(Panel* panel, const gfx::Point& position) = 0;

[jennb, 2012/03/01 00:33:38]

Is the origin of the panel placed close to |position|? Could you explain more?

[jianli, 2012/03/02 22:42:43]

Renamed this method to AddDraggingPanel to mean it is only intended to be user
for adding dragging panel from another strip. Also updated the comment to remove
"close to position" since indeed we now place the panel at position.

+
   // Removes |panel| from the collection of panels. Invoked asynchronously
   // after a panel has been closed.
   // Returns |false| if the panel is not in the strip.
   virtual bool RemovePanel(Panel* panel) = 0;
 
   // Closes all panels in the collection. Panels will be removed after closing.
   virtual void CloseAll() = 0;
 
   // Resizes the |panel| to the |preferred_window_size| and updates the layout
   // of other panels in the collection accordingly.
@@ skipping 29 matching lines @@
   virtual void EndDraggingPanel(Panel* panel, bool cancelled) = 0;
 
  protected:
   explicit PanelStrip(Type type);
   virtual ~PanelStrip();
 
   const Type type_;  // Type of this panel strip.
 };
 
 #endif  // CHROME_BROWSER_UI_PANELS_PANEL_STRIP_H_