gtk:drag-set-icon-surface (context surface)

context -- a gdk:drag-context object for a drag, this must be called with a drag context for the source side of a drag
surface -- a cairo:surface-t surface to use as icon

Sets the Cairo surface as the icon for a given drag. GTK retains references for the arguments, and will release them when they are no longer needed.

To position the surface relative to the mouse, use the cairo:surface-set-device-offset function on the surface. The mouse cursor will be positioned at the (0,0) coordinate of the surface.