Drag and Drop: Implementing a Drop Target

 

The latest version of this topic can be found at Drag and Drop: Implementing a Drop Target.

This article outlines how to make your application a drop target. Implementing a drop target takes slightly more work than implementing a drop source, but it is still relatively simple. These techniques also apply to non-OLE applications.

To implement a drop target

1. Add a member variable to each view in the application that you want to be a drop target. This member variable must be of type COleDropTarget or a class derived from it.

2. From your view class's function that handles the WM_CREATE message (typically OnCreate), call the new member variable's Register member function. Revoke will be called automatically for you when your view is destroyed.

3. Override the following functions. If you want the same behavior throughout your application, override these functions in your view class. If you want to modify behavior in isolated cases or want to enable dropping on non-CView windows, override these functions in your COleDropTarget-derived class.

   Override	To allow
   OnDragEnter	Drop operations to occur in the window. Called when the cursor first enters the window.
   OnDragLeave	Special behavior when the drag operation leaves the specified window.
   OnDragOver	Drop operations to occur in the window. Called when the cursor is being dragged across the window.
   OnDrop	Handling of data being dropped into the specified window.
   OnScrollBy	Special behavior for when scrolling is necessary in the target window.

See the MAINVIEW.CPP file that is part of the MFC OLE sample OCLIENT for an example of how these functions work together.

For more information, see:

• Implementing a Drop Source

• Creating and Destroying OLE Data Objects and Data Sources

• Manipulating OLE Data Objects and Data Sources

See Also

Drag and Drop (OLE)
COleDropTarget Class