An application can pass NULL as the ulData parameter of the WinSetClipbrdData function instead of a pointer or a handle. This indicates that the data is rendered only when another application requests it from the clipboard. This is useful if an application supports several clipboard formats that are time-consuming to render. With delayed rendering, an application can send NULL handles for each clipboard format that it supports and render individual formats only when the format actually is requested from the clipboard. An application can either write data for standard formats or choose delayed rendering for more complex formats.

When an application uses delayed rendering for one or more of its clipboard formats, it must become the clipboard owner. As long as the application is the clipboard owner, it receives a WM_RENDERFMT message whenever a request is received by the clipboard for a format using delayed rendering. When the application receives such a message, it renders the data and passes the pointer or handle to the clipboard by calling the WinSetClipbrdData function. The rules for shared-memory access for rendered data are the same as those for standard clipboard data. This simply is a delayed execution of the operation that occurs if the data does not have delayed rendering.

The clipboard owner, with one or more delayed-rendering formats on the clipboard, receives a WM_RENDERALLFMTS message just before the clipboard-owner application terminates. This ensures that the application renders all of its data before terminating.