Support dragging panels to stack and snap.

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_
 
 #include "base/memory/scoped_ptr.h"
-#include "ui/gfx/point.h"
+#include "chrome/browser/ui/panels/panel_collection.h"
 #include "ui/gfx/vector2d.h"
 
 class Panel;
 class PanelCollection;
 class PanelManager;
+namespace gfx {
+class Point;
+class Rect;
+}
 
 // Controls all the drags initiated for all panels, including detaching,
 // docking, stacking, snapping and intra-collection dragging.
 class PanelDragController {
  public:
   explicit PanelDragController(PanelManager* panel_manager);
   ~PanelDragController();
 
   // 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 is_dragging() const { return dragging_panel_ != NULL; }
   Panel* dragging_panel() const { return dragging_panel_; }
 
   // For testing.
   static int GetDetachDockedPanelThresholdForTesting();
   static int GetDockDetachedPanelThresholdForTesting();
+  static int GetGluePanelDistanceThresholdForTesting();
+  static int GetGluePanelOverlapThresholdForTesting();
 
  private:
+  enum GlueAction {
+    STACK,
+    SNAP
+  };
+
+  enum GlueEdge {
+    TOP_EDGE,
+    BOTTOM_EDGE,
+    LEFT_EDGE,
+    RIGHT_EDGE
+  };
+
   gfx::Point GetPanelPositionForMouseLocation(
       const gfx::Point& mouse_location) const;
 
   // |target_position| is in screen coordinate systems. It contains the proposed
   //  panel origin to move to. Returns true if the request has been performed.
-  bool TryDetach(const gfx::Point& target_position);
-  bool TryDock(const gfx::Point& target_position);
+  void TryDetach(const gfx::Point& target_position);
+  void TryDock(const gfx::Point& target_position);
+  void TryStack(const gfx::Point& target_position);
+  bool TryUnstackFromTop(const gfx::Point& target_position);
+  bool TryUnstackFromBottom(const gfx::Point& target_position);
+  void TrySnap(gfx::Point* target_position);
+
+  // Finds the panel that the dragging panel with |potential_position| could
+  // snap to or stack with. If such panel is found, |target_bounds| contains the
+  // new bounds for the dragging panel and |target_edge| contains the matched
+  // edge.
+  Panel* FindPanelToGlue(const gfx::Point& potential_position,
+                         GlueAction action,
+                         gfx::Rect* target_bounds,
+                         GlueEdge* target_edge) const;
+
+  // Moves the |panel| (and all panels below if it is in a stack) to a different
+  // collection.
+  void MovePanelAndBelowToCollection(
+      Panel* panel,
+      PanelCollection* target_collection,
+      PanelCollection::PositioningMask positioning_mask) const;
 
   PanelManager* panel_manager_;  // Weak, owns us.
+  bool panel_stacking_enabled_;
 
   // Panel currently being dragged.
   Panel* dragging_panel_;
 
   // The original panel collection when the drag is started.
   PanelCollection* dragging_panel_original_collection_;
 
   // The offset from mouse location to the panel position when the drag
   // starts.
   gfx::Vector2d offset_from_mouse_location_on_drag_start_;
 
   DISALLOW_COPY_AND_ASSIGN(PanelDragController);
 };
 
 #endif  // CHROME_BROWSER_UI_PANELS_PANEL_DRAG_CONTROLLER_H_