Support detaching/attaching panels via inter-strip drags.

chrome/browser/ui/panels/panel_drag_controller.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_DRAG_CONTROLLER_H_
 #define CHROME_BROWSER_UI_PANELS_PANEL_DRAG_CONTROLLER_H_
 #pragma once
 
 #include <set>
 #include "base/basictypes.h"
 #include "ui/gfx/point.h"
 
 class Panel;
+class PanelManager;
+class PanelStrip;
 
 // Responsible for handling drags initiated for all panels, including both
 // intra-strip and inter-strip drags.
 class PanelDragController {
  public:
-  PanelDragController();
+  explicit PanelDragController(PanelManager* panel_manager);
   ~PanelDragController();
 
-  void StartDragging(Panel* panel);
-  void Drag(int delta_x, int delta_y);
+  // Drags the given panel.
+  // |mouse_location| is in screen coordinate system.
+  void StartDragging(Panel* panel, const gfx::Point& mouse_location);
+  void Drag(const gfx::Point& mouse_location);
   void EndDragging(bool cancelled);
 
   // Asynchronous confirmation of panel having been closed.
   void OnPanelClosed(Panel* panel);
 
   bool IsDragging() const { return dragging_panel_ != NULL; }
 
   Panel* dragging_panel() const { return dragging_panel_; }
-  gfx::Point dragging_panel_original_position() const {
-    return dragging_panel_original_position_;
+
+#ifdef UNIT_TEST
+  static int GetDetachDockedPanelThreshold() {
+    return kDetachDockedPanelThreshold;
   }
 
+  static int GetDockDetachedPanelThreshold() {
+    return kDockDetachedPanelThreshold;
+  }
+#endif
+
  private:
+  // Used to figure out if the panel can be dragged to other strip.
+  PanelStrip* ComputeDragTagetStrip(
+      const gfx::Point& mouse_location, gfx::Point* new_panel_position) const;
+  bool CanDragToDockedStrip(
+      const gfx::Point& mouse_location, gfx::Point* new_panel_position) const;
+  bool CanDragToDetachedStrip(
+      const gfx::Point& mouse_location, gfx::Point* new_panel_position) const;
+
+  PanelManager* panel_manager_;  // Weak, owns us.
+
   // Panel currently being dragged.
   Panel* dragging_panel_;
 
-  // Original position, in screen coordinate system, 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_;
+  // The original panel strip that the drag is initiated.

[jennb, 2012/03/03 02:19:33]

Fix grammar. 

[jianli, 2012/03/07 19:14:31]

Done.

+  PanelStrip* dragging_panel_original_strip_;
+
+  // The mouse location, in screen coordinates, when mouse press/drag event is
+  // received last time.

[jennb, 2012/03/03 02:19:33]

'last time' ? 

[jianli, 2012/03/07 19:14:31]

Done.

+  gfx::Point last_mouse_location_;
+
+  // The mouse location, in screen coordinates, when the drag starts at the
+  // docked strip.
+  gfx::Point mouse_location_on_docked_;
+
+  // The threshold to detach a docked panel to make it free-floating.

[jennb, 2012/03/03 02:19:33]

These comments simply repeat the var name. Explain what is being measured, i.e.
change in y direction from original drag position or distance of bottom edge of
panel from bottom of docked strip.

[jianli, 2012/03/07 19:14:31]

Done.

+  static const int kDetachDockedPanelThreshold;
+
+  // The threshold to dock a detached panel.
+  static const int kDockDetachedPanelThreshold;
 
   DISALLOW_COPY_AND_ASSIGN(PanelDragController);
 };
 
 #endif  // CHROME_BROWSER_UI_PANELS_PANEL_DRAG_CONTROLLER_H_