function theResult = doubleclick

% doubleclick -- Trap for double-clicks.
%  doubleclick (no argument) returns TRUE if a click
%   is detected while "doubleclick" itself is executing;
%   otherwise, FALSE.  Call "doubleclick" at the top
%   of a "WindowButtonDown" or "ButtonDown" callback.
%   The 'Interruptible' property of the callback-object
%   must be 'on'.  The double-click time is 0.5 sec.
%   A valid double-click causes two values to be returned
%   in succession: first, a logical(1), then [].  The
%   latter can be ignored; it represents the first click
%   that initiated the process.  For a valid single-click,
%   only logical(0) is returned.
 
% Copyright (C) 1997 Dr. Charles R. Denham, ZYDECO.
%  All Rights Reserved.
%   Disclosure without explicit written consent from the
%    copyright owner does not constitute publication.
 
% Version of 25-Jul-1998 09:47:16.
% Updated    21-Oct-1998 10:14:18.

global CLICK_COUNT   % Use "persistent in Matlab 5.2+.

% Increase the following if the
%  double-click-time seems too short.

DOUBLE_CLICK_TIME = 1/2;   % Seconds.

if isempty(CLICK_COUNT), CLICK_COUNT = 0; end

CLICK_COUNT = CLICK_COUNT + 1;

if CLICK_COUNT == 1
	tic
	while isequal(CLICK_COUNT, 1) & toc < DOUBLE_CLICK_TIME, end
end

drawnow   % Process the event-cue.

% Note:
%  Despite the "drawnow" seen above, Matlab does not
%  update the "SelectionType" in timely fashion, so
%  it cannot be used to trap a double-click properly.

result = (CLICK_COUNT > 1);

CLICK_COUNT = [];

if nargout > 0
	theResult = result;
else
	disp(result)
end