function putFixation(win,X,Y,color);
%  putFixation(win,X,Y,color);
% apply fixation point to window (or windows) win,
% using the specified color from the clut.
% X and Y are the screen size; they're gotten from 
% the screen if not specified.
if ~exist('color','var')	color = 255;	end
if nargin < 4
	rect = screen(win(1),'Rect');
	X = rect(3); Y = rect(4);
end
for i = 1:length(win)
	screen(win(i), 'FillRect', color, centerrect([0 0 2 6], [0 0 X Y]));
	screen(win(i), 'FillRect', color, centerrect([0 0 6 2], [0 0 X Y]));
end
return
