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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:

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