display-sub : Make a child visual that is a window to the parent
Creates a "child" visual within a "parent". This can be thought of as a window and the display-sub target is intended for simple windowing systems.
No textual arguments, since this target can only be used by applications. :p:`argptr` must contain the parent visual.
The sub target behaves a bit special with respect to (i.e. abuses the semantics of :) the :man:`ggiSetMode(3)` call. It uses the "visible" size for the top left corner position of the window within the visual, and the "virtual" size for window width and height. Note, that moving/resizing the window does not cause any drawing action. You have to perform those yourself. All it does for you is providing a virtual visual within an existing one, which is convenient to allow for window system canvases to be about any GGI program.