Emitted when the dropped content is preloaded for the item at index.
In order for data to be preloaded, [property@Sidebar:drop-preload] must be set to `TRUE`.
The content must be of one of the types set up via [method@Sidebar.setup_drop_target].
See [property@Gtk.DropTarget:value].
| index |
index of the hovered item |
| value |
the `GValue` being dropped |
|
the preferred action for the drop |