the source widget.
The targets (data formats) in which the source can provide the data.
A bitmask of the allowed drag actions for this drag.
The button the user clicked to start the drag.
The event that triggered the start of the drag.
the context for this drag. [transfer none]
Initiates a drag on the source side. The function only needs to be used when the application is starting drags itself, and is not needed when gtk_drag_source_set() is used. The event is used to retrieve the timestamp that will be used internally to grab the pointer. If event is NULL, then GDK_CURRENT_TIME will be used. However, you should try to pass a real event in all cases, since that can be used by GTK+ to get information about the start position of the drag, for example if the event is a GDK_MOTION_NOTIFY. Generally there are three cases when you want to start a drag by hand by calling