Sets a paintable to use as icon during DND operations.
The hotspot coordinates determine the point on the icon that gets aligned with the hotspot of the cursor.
If paintable is null, a default icon is used.
This function can be called before a drag is started, or in a [signal@Gtk.DragSource::prepare] or [signal@Gtk.DragSource:
:drag-begin] signal handler.
| this |
a `GtkDragSource` |
| hot_x |
the hotspot X coordinate on the icon |
| hot_y |
the hotspot Y coordinate on the icon |
| paintable |
the `GdkPaintable` to use as icon |