The fix is simpl to make blitTextInPlace center text to the
screen rather than the text creation doing it. That way you don't
get weird behavior with screen_blitText (which already handles centering).
Problem 1: fullscreen switching was leaving artifacts. Fixed by
drawing all black when switching fullscreen (and switching fullscreen
is now handled by its own function).
Problem 2: the mission briefing screen would distort if you changed
fullscreen during it. Fixed by redrawing the screen (it was previously
only drawn once).
Julie Marchant