NAME
        ObtainGIRPort -- Set up a rastport for a custom gadget. (v36)

    SYNOPSIS
        RPort = ObtainGIRPort( GInfo )
        D0                     A0

        struct rastport *obtaingirport( struct gadgetinfo * );

    FUNCTION
        Sets up a rastport for use (only) by custom gadget hook routines.
        This function must be called EACH time a hook routine needing
        to perform gadget rendering is called, and must be accompanied
        by a corresponding call to releasegirport().

        Note that if a hook function passes you a rastport pointer,
        e.g., GM_RENDER, you needn't call ObtainGIRPort() in that case.

    INPUTS
        A pointer to a gadgetinfo structure, as passed to each custom
        gadget hook function.

    RESULT
        A pointer to a rastport that may be used for gadget rendering.
        This pointer may be NULL, in which case you should do no rendering.
        You may (optionally) pass a null return value to releasegirport().

    BUGS

    SEE ALSO
        releasegirport(), custom gadget documentation