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_ 108
