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_;
   }
+  bool has_dragged_to_other_strip() const {
+    return has_dragged_to_other_strip_;
+  }
 
  private:
+  // Returns the panel strip to drag to.
+  PanelStrip* CanDragToDockedStrip(const gfx::Point& mouse_location) const;
+  PanelStrip* CanDragToDetachedStrip(const gfx::Point& mouse_location) const;
+
+  // Helper method to transit the dragging panel to the new strip at the new
+  // position.
+  static void MoveToStrip(Panel* panel,
+                          PanelStrip* new_strip,
+                          const gfx::Point& new_position);
+
+  PanelManager* panel_manager_;  // Weak, owns us.
+
   // Panel currently being dragged.
   Panel* dragging_panel_;
 
-  // Original position, in screen coordinate system, of the panel being dragged.
+  // The original panel strip that the drag is initiated.
+  PanelStrip* dragging_panel_original_strip_;
+
+  // Original position, in screen coordinates, 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 mouse location, in screen coordinates, when mouse press/drag event is
+  // received last time.
+  gfx::Point last_mouse_location_;
+
+  // When the panel is dragged within the docked strip, y delta of the drag is
+  // not applied to new panel position. We need to keep track of the total
+  // omitted delta values so that the panel can jump immediately to the position
+  // where the panel detach is triggered.
+  int total_ommitted_delta_y_;
+
+  // The flag that indicates if the dragging panel has ever been dragged into
+  // other strip.
+  bool has_dragged_to_other_strip_;
+
   DISALLOW_COPY_AND_ASSIGN(PanelDragController);
 };
 
 #endif  // CHROME_BROWSER_UI_PANELS_PANEL_DRAG_CONTROLLER_H_