public void set_width (float width)
Forces a width on an actor, causing the actor's preferred width and height (if any) to be ignored.
width is -1 the actor will use its preferred width request instead of overriding it, i.e. you can "unset" the width with -1.
This function sets both the minimum and natural size of the actor.
Requested new width for the actor, in pixels, or -1