This notification code is sent to the owner of the container when a lazy drag operation is commenced over a container. (The container control receives a WM_PICKUP message.)

The CN_PICKUP message handler determines if the mouse is over an object or in white space of the client window.

If a pickup object is not selected, only that pickup object is added to the lazy drag set. If the pickup object is selected, all selected items in the container are added to the lazy drag set. The shell sets the CRA_PICKED attributes for all objects that are picked.