The getactivepage function is available in the winbgim implementation of
BGI graphics. getactivepage gets the page number of the currently active
page (where drawing takes place).
The active graphics page might not be the one you see onscreen, depending
on how many graphics pages are available on your system.
The original winbgi was designed to support up to 16 pages, but I have
only used pages 1 and 2 myself. NOTE: Using page number 0 might mess up
the colors. I use pages 1-2 for double buffering.