rectcopy in overlay planes - VGX

[Ken Chin-Purcell]

I would like to scroll text in the overlay planes, but rectcopy is misbehaving.
For instance, the following core dumps:

#include <gl.h>

main()
{
    long        winID;

    prefsize(300, 200);
    foreground();
    winID = winopen("rectcopy");
    clear();

    drawmode(OVERDRAW);
    mapcolor(1, 255, 255, 255);
    color(1);
    cmov2i(50, 50);
    charstr("try me out for size");

    rectcopy(50, 50, 200, 100, 10, 10);         /* bombola! */

    drawmode(NORMALDRAW);
    pause();
}

Take out the 'drawmode(OVERDRAW);' and it works as expected.
By trial and error I've discovered that setting 'overlay(4)'
avoids a core dump, but produces strange results.

Could some kind soul show me the light?  Thanks.

--
--  Ken