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function [avail, numChars] = CharAvail
% [avail, numChars] = CharAvail
%
% CharAvail returns the availability of characters in the keyboard event
% queue and sometimes the queue's current size. "avail" will be 1 if characters are
% available, 0 otherwise. "numChars" may hold the current number of
% characters in the event queue, but in some system configurations it is
% just empty, so do not rely on numChars providing meaningful results,
% unless you've tested it on your specific setup.
%
% Note that this routine does not actually remove characters from the event
% queue. Call GetChar to remove characters from the queue.
%
% CharAvail works on all platforms with Matlab and Java enabled. It works
% also on M$-Windows under matlab -nojvm mode. It does not work on OS-X or
% Linux in Matlab -nojvm mode and it also doesn't work under GNU/Octave.
%
% GetChar and CharAvail are character-oriented (and slow), whereas KbCheck
% and KbWait are keypress-oriented (and fast). See KbCheck.
%
% See also: GetChar, ListenChar, FlushEvents, KbCheck, KbWait, KbDemo, Screen Preference Backgrounding.
% 11/5/94 dhb Added caveat about delay.
% 1/22/97 dhb Added comment and pointer to TIMER routines.
% 3/6/97 dhb Updated for KbWait, KbCheck.
% 8/2/97 dgp Explain difference between key and character. See KbCheck.
% 8/16/97 dgp Call the new EventAvail.mex instead of the obsolete KbHit.mex.
% 3/24/98 dgp Explain backgrounding. Omit obsolete GetKey and KbHit.
% 3/19/99 dgp Update explanation of backgrounding.
% 3/28/99 dgp Show how to turn off backgrounding.
% 3/8/00 emw Added PC comments
% 3/12/00 dgp Fix platform dependency test.
% 9/20/05 awi Removed outdated notice in help mentioning problems with
% CharAvail on Windows. The Problem was fixed.
% Added platform conditional for OS X ('MAC').
% 1/22/06 awi Commented out Cocoa wrapper version and wrote Java wrapper.
% 3/28/06 awi Detect buffer overflow.
% 6/20/06 awi Use AddPsychJavaPath instead of AssertGetCharJava.
% 8/16/06 cgb Now using a much faster method to get characters in Matlab.
% We now read straight from the keyboard event manager in
% java.
% 9/18/06 mk CharAvail now works on all Matlabs (OS-X, Windows) in JVM
% mode. In -nojvm mode on Windows, it falls back to the old
% Windows DLL ...
%
% 05/31/09 mk Add support for Octave and Matlab in noJVM mode.
global OSX_JAVA_GETCHAR;
persistent isjavadesktop;
% Only check this once because psychusejava is a slow command.
if isempty(isjavadesktop)
isjavadesktop = psychusejava('desktop');
end
if isjavadesktop
% Make sure that the GetCharJava class is loaded and registered with
% the java focus manager.
if isempty(OSX_JAVA_GETCHAR)
try
OSX_JAVA_GETCHAR = AssignGetCharJava;
catch
error('Could not load Java class GetCharJava! Read ''help PsychJavaTrouble'' for help.');
end
OSX_JAVA_GETCHAR.register;
end
% Check to see if any characters are available.
avail = OSX_JAVA_GETCHAR.getCharCount;
% Make sure that there isn't a buffer overflow.
if avail == -1
error('GetChar buffer overflow. Use "FlushEvents" to clear error');
end
numChars = avail;
avail = avail > 0;
return;
else
% Java VM unavailable, i.e., running in -nojvm mode.
% On Windows, we can fall back to the old CharAvail.dll.
if IsWin & ~IsOctave %#ok<AND2>
% CharAvail.dll has been renamed to CharAvailNoJVM.dll. Call it.
avail = CharAvailNoJVM;
numChars = [];
return;
end
end
% Running either on Octave or on OS/X or Linux with Matlab in No JVM mode:
drawnow;
if exist('fflush')
builtin('fflush', 1);
end
% Screen's GetMouseHelper with command code 14 delivers
% count of currently pending characters on stdin:
avail = Screen('GetMouseHelper', -14);
numChars = avail;
avail = avail > 0;
return;
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