DropTargetAsync

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 class@Gtk.DropTarget, 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 method@Gtk.Widget.add_controller.

During a drag operation, the first signal that a GtkDropTargetAsync emits is signal@Gtk.DropTargetAsync::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 signal@Gtk.DropTargetAsync::drag-enter signal, followed by signal@Gtk.DropTargetAsync::drag-motion signals as the pointer moves, optionally a signal@Gtk.DropTargetAsync::drop signal when a drop happens, and finally a signal@Gtk.DropTargetAsync::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 method@Gdk.Drop.finish.

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.