getIntrinsicWidth
Gets the preferred width the @paintable would like to be displayed at.
Consumers of this interface can use this to reserve enough space to draw the paintable.
This is a purely informational value and does not in any way limit the values that may be passed to method@Gdk.Paintable.snapshot.
If the @paintable does not have a preferred width, it returns 0. Negative values are never returned.
Return
the intrinsic width of @paintable or 0 if none.