Refactors RootViewDropTarget into a platform independent part,

DropHelper, and the platform specific part DropTarget. I've also moved
ownership/creation of the DropTarget to Widget. This makes it alot
easier for the windows side, in which DropTarget must implement
IDataObject.

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/165155

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@23020 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 104 insertions, 0 deletions

diff --git a/views/widget/drop_helper.h b/views/widget/drop_helper.h
new file mode 100644
index 0000000..63bfa27
--- /dev/null
+++ b/views/widget/drop_helper.h
@@ -0,0 +1,104 @@
+// Copyright (c) 2006-2008 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 VIEWS_WIDGET_DROP_HELPER_H_
+#define VIEWS_WIDGET_DROP_HELPER_H_
+
+#include "base/basictypes.h"
+
+class OSExchangeData;
+
+namespace gfx {
+class Point;
+}  // namespace gfx
+
+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(RootView* 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.
+  RootView* 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.
+  RootView* 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  // VIEWS_WIDGET_DROP_HELPER_H_