window_get_fullscreen();
Returns: Boolean
This function returns whether the game window is in fullscreen
mode (true) or not (false).
if window_get_fullscreen()
{
draw_text(32, 32, "Fullscreen is ON");
}
else {
draw_text(32, 32, "Fullscreen is OFF");
}
The above code will check to see if the window is in full screen mode or not and draw a text message depending on the returned value.