GtkDropTargetAsync

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 GtkDropTarget, 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 gtk_widget_add_controller().

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