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// Copyright (c) 2011 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 UI_VIEWS_WIDGET_DROP_HELPER_H_
#define UI_VIEWS_WIDGET_DROP_HELPER_H_
#pragma once
#include "base/basictypes.h"
namespace gfx {
class Point;
} // namespace gfx
namespace ui {
class OSExchangeData;
} // namespace ui
using ui::OSExchangeData;
namespace views {
class RootView;
class View;
// DropHelper provides support for managing the view a drop is going to occur
// at during dnd as well as sending the view the appropriate dnd methods.
// DropHelper is intended to be used by a class that interacts with the system
// drag and drop. The system class invokes OnDragOver as the mouse moves,
// then either OnDragExit or OnDrop when the drop is done.
class DropHelper {
public:
explicit DropHelper(View* root_view);
~DropHelper();
// Current view drop events are targeted at, may be NULL.
View* target_view() const { return target_view_; }
// Returns the RootView the DropHelper was created with.
View* root_view() const { return root_view_; }
// Resets the target_view_ to NULL if it equals view.
//
// This is invoked when a View is removed from the RootView to make sure
// we don't target a view that was removed during dnd.
void ResetTargetViewIfEquals(View* view);
// Invoked when a the mouse is dragged over the root view during a drag and
// drop operation. This method returns a bitmask of the types in DragDropTypes
// for the target view. If no view wants the drop, DRAG_NONE is returned.
int OnDragOver(const OSExchangeData& data,
const gfx::Point& root_view_location,
int drag_operation);
// Invoked when a the mouse is dragged out of the root view during a drag and
// drop operation.
void OnDragExit();
// Invoked when the user drops data on the root view during a drag and drop
// operation. See OnDragOver for details on return type.
//
// NOTE: implementations must invoke OnDragOver before invoking this,
// supplying the return value from OnDragOver as the drag_operation.
int OnDrop(const OSExchangeData& data,
const gfx::Point& root_view_location,
int drag_operation);
// Calculates the target view for a drop given the specified location in
// the coordinate system of the rootview. This tries to avoid continually
// querying CanDrop by returning target_view_ if the mouse is still over
// target_view_.
View* CalculateTargetView(const gfx::Point& root_view_location,
const OSExchangeData& data,
bool check_can_drop);
private:
// Implementation of CalculateTargetView. If |deepest_view| is non-NULL it is
// set to the deepest descendant of the RootView that contains the point
// |root_view_location|
View* CalculateTargetViewImpl(const gfx::Point& root_view_location,
const OSExchangeData& data,
bool check_can_drop,
View** deepest_view);
// Methods to send the appropriate drop notification to the targeted view.
// These do nothing if the target view is NULL.
void NotifyDragEntered(const OSExchangeData& data,
const gfx::Point& root_view_location,
int drag_operation);
int NotifyDragOver(const OSExchangeData& data,
const gfx::Point& root_view_location,
int drag_operation);
void NotifyDragExit();
// RootView we were created for.
View* root_view_;
// View we're targeting events at.
View* target_view_;
// The deepest view under the current drop coordinate.
View* deepest_view_;
DISALLOW_COPY_AND_ASSIGN(DropHelper);
};
} // namespace views
#endif // UI_VIEWS_WIDGET_DROP_HELPER_H_