`GtkDropTargetAsync` is an event controller to receive Drag-and-Drop operations, asynchronously.
It is the more complete but also more complex method of handling drop operations compared to [[email protected]], and you should only use it if `GtkDropTarget` doesn't provide all the features you need.
To use a `GtkDropTargetAsync` to receive drops on a widget, you create a `GtkDropTargetAsync` object, configure which data formats and actions you support, connect to its signals, and then attach it to the widget with [[email protected]_controller].
During a drag operation, the first signal that a `GtkDropTargetAsync` emits is [[email protected]:
GtkDropTargetAsync:accept], which is meant to determine whether the target is a possible drop site for the ongoing drop. The
default handler for the accept signal accepts the drop if it finds a
compatible data format and an action that is supported on both sides.
If it is, and the widget becomes a target, you will receive a [[email protected]:GtkDropTargetAsync:drag-enter]
signal, followed by [[email protected]:GtkDropTargetAsync:drag-motion] signals as the pointer moves, optionally a [
[email protected]:GtkDropTargetAsync:drop] signal when a drop happens, and finally a [[email protected]:
GtkDropTargetAsync:drag-leave] signal when the pointer moves off the widget.
The drag_enter and drag_motion handler return a `GdkDragAction` to update the status of the ongoing operation. The drop handler should decide if it ultimately accepts the drop and if it does, it should initiate the data transfer and finish the operation by calling [[email protected]].
Between the drag_enter and drag_leave signals the widget is a current drop target, and will receive the gtk_state_flag_drop_active state, which can be used by themes to style the widget as a drop target.