Refactor intra-strip panel drags by introducing PanelDragController.

chrome/browser/ui/panels/detached_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_DETACHED_PANEL_STRIP_H_
 #define CHROME_BROWSER_UI_PANELS_DETACHED_PANEL_STRIP_H_
 #pragma once
 
 #include <set>
 #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;
 class PanelManager;
 
 // This class manages a group of free-floating panels.
 class DetachedPanelStrip : public PanelStrip {
  public:
   typedef std::set<Panel*> Panels;
 
   explicit DetachedPanelStrip(PanelManager* panel_manager);
   virtual ~DetachedPanelStrip();
 
   // PanelStrip OVERRIDES:
   virtual void SetDisplayArea(const gfx::Rect& display_area) OVERRIDE;
   virtual void RefreshLayout() OVERRIDE;
   virtual void AddPanel(Panel* panel) OVERRIDE;
   virtual bool RemovePanel(Panel* panel) OVERRIDE;
   virtual void CloseAll() OVERRIDE;
   virtual void ResizePanelWindow(
       Panel* panel,
       const gfx::Size& preferred_window_size) OVERRIDE;
   virtual void OnPanelAttentionStateChanged(Panel* panel) OVERRIDE;
   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_; }
 
  private:
   PanelManager* panel_manager_;  // Weak, owns us.
 
   // All panels in the panel strip must fit within this area.
   gfx::Rect display_area_;
 
   // 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);
 };
 
 #endif  // CHROME_BROWSER_UI_PANELS_DETACHED_PANEL_STRIP_H_