ui/views/widget/drop_helper.h

   1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef UI_VIEWS_WIDGET_DROP_HELPER_H_
   6 #define UI_VIEWS_WIDGET_DROP_HELPER_H_
   7
   8 #include "base/basictypes.h"
   9
  10 namespace gfx {
  11 class Point;
  12 }  // namespace gfx
  13
  14 namespace ui {
  15 class OSExchangeData;
  16 }  // namespace ui
  17 using ui::OSExchangeData;
  18
  19 namespace views {
  20
  21 class RootView;
  22 class View;
  23
  24 // DropHelper provides support for managing the view a drop is going to occur
  25 // at during dnd as well as sending the view the appropriate dnd methods.
  26 // DropHelper is intended to be used by a class that interacts with the system
  27 // drag and drop. The system class invokes OnDragOver as the mouse moves,
  28 // then either OnDragExit or OnDrop when the drop is done.
  29 class DropHelper {
  30  public:
  31   explicit DropHelper(View* root_view);
  32   ~DropHelper();
  33
  34   // Current view drop events are targeted at, may be NULL.
  35   View* target_view() const { return target_view_; }
  36
  37   // Returns the RootView the DropHelper was created with.
  38   View* root_view() const { return root_view_; }
  39
  40   // Resets the target_view_ to NULL if it equals view.
  41   //
  42   // This is invoked when a View is removed from the RootView to make sure
  43   // we don't target a view that was removed during dnd.
  44   void ResetTargetViewIfEquals(View* view);
  45
  46   // Invoked when a the mouse is dragged over the root view during a drag and
  47   // drop operation. This method returns a bitmask of the types in DragDropTypes
  48   // for the target view. If no view wants the drop, DRAG_NONE is returned.
  49   int OnDragOver(const OSExchangeData& data,
  50                  const gfx::Point& root_view_location,
  51                  int drag_operation);
  52
  53   // Invoked when a the mouse is dragged out of the root view during a drag and
  54   // drop operation.
  55   void OnDragExit();
  56
  57   // Invoked when the user drops data on the root view during a drag and drop
  58   // operation. See OnDragOver for details on return type.
  59   //
  60   // NOTE: implementations must invoke OnDragOver before invoking this,
  61   // supplying the return value from OnDragOver as the drag_operation.
  62   int OnDrop(const OSExchangeData& data,
  63              const gfx::Point& root_view_location,
  64              int drag_operation);
  65
  66   // Calculates the target view for a drop given the specified location in
  67   // the coordinate system of the rootview. This tries to avoid continually
  68   // querying CanDrop by returning target_view_ if the mouse is still over
  69   // target_view_.
  70   View* CalculateTargetView(const gfx::Point& root_view_location,
  71                             const OSExchangeData& data,
  72                             bool check_can_drop);
  73
  74  private:
  75   // Implementation of CalculateTargetView. If |deepest_view| is non-NULL it is
  76   // set to the deepest descendant of the RootView that contains the point
  77   // |root_view_location|
  78   View* CalculateTargetViewImpl(const gfx::Point& root_view_location,
  79                                 const OSExchangeData& data,
  80                                 bool check_can_drop,
  81                                 View** deepest_view);
  82
  83   // Methods to send the appropriate drop notification to the targeted view.
  84   // These do nothing if the target view is NULL.
  85   void NotifyDragEntered(const OSExchangeData& data,
  86                          const gfx::Point& root_view_location,
  87                          int drag_operation);
  88   int NotifyDragOver(const OSExchangeData& data,
  89                      const gfx::Point& root_view_location,
  90                      int drag_operation);
  91   void NotifyDragExit();
  92
  93   // RootView we were created for.
  94   View* root_view_;
  95
  96   // View we're targeting events at.
  97   View* target_view_;
  98
  99   // The deepest view under the current drop coordinate.
 100   View* deepest_view_;
 101
 102   DISALLOW_COPY_AND_ASSIGN(DropHelper);
 103 };
 104
 105 }  // namespace views
 106
 107 #endif  // UI_VIEWS_WIDGET_DROP_HELPER_H_