a GtkWidget which should be a drag destination for palette
the flags that specify what actions GTK+ should take for drops on that widget
the GtkToolPaletteDragTargets which the widget should support
the GdkDragActions which the widget should suppport
Sets palette as drag source (see gtk_tool_palette_set_drag_source()) and sets widget as a drag destination for drags from palette. See gtk_drag_dest_set(). Since 2.20