window_get_fullscreen

This function returns whether the game window is in fullscreen mode (true) or not (false).

Syntax:

window_get_fullscreen();

Returns:

Boolean

Example:

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.