I noticed that in the zoom menu under v.digit is:
switch (button)
{
case LEFTB:
set_window_w_mouse ();
clear_window();
replot(CMap);
....
It clears and redraws the map after a right click to leave the
set_window_w_mouse submenu. This appears to be unnecessary because the
screen is either already refreshed or nothing has changed when these lines
are executed. Unless I am missing someting, we can save unnecessary
graphics redisplay time by commenting out lines 679-690 in window.c (line
numbers from ver 1.7).
/* clear_window();
replot(CMap); */