Clipboard Ownership

The clipboard owner is the window associated with the information on the clipboard. A window becomes the clipboard owner when it places data on the clipboard — specifically, when it calls the EmptyClipboard function. The window remains the clipboard owner until it is closed or another window empties the clipboard.

When the clipboard is emptied, the clipboard owner receives a WM_DESTROYCLIPBOARD message. Following are some reasons why a window might process this message:

• The window delayed rendering of one or more clipboard formats. In response to the WM_DESTROYCLIPBOARD message, the window might free resources it had allocated in order to render data on request. For more information about the rendering of data, see Delayed Rendering.
• The window placed data on the clipboard in a private clipboard format. The data for private clipboard formats is not freed by the system when the clipboard is emptied. Therefore, the clipboard owner should free the data upon receiving the WM_DESTROYCLIPBOARD message. For more information about private clipboard formats, see Clipboard Formats.
• The window placed data on the clipboard using the CF_OWNERDISPLAY clipboard format. In response to the WM_DESTROYCLIPBOARD message, the window might free resources it had used to display information in the clipboard viewer window. For more information about this alternative format, see Owner-Display Format.