% KbPractice.m
% Displays the number of seconds that have elapsed
% when the user presses a key.
% a simplified version of KbDemo modified by YW, 2022

KbName('UnifyKeyNames');
WaitSecs(1.0);
disp('Testing KbCheck and KbName: press a key to see its number');
disp('Press the ''SPACE'' key to exit.');
escapeKey = KbName('SPACE');
ListenChar(2);
while KbCheck; end % Wait until all keys are released.
% This is a loop that flips around doing anything as long as KbCheck
% reports back that a key is pressed on the keyboard. Means that the
% program doesnĄ¯t continue until all keys have been released.

startSecs = GetSecs;
while 1
    % while 1 is always true, so this loop will continue indefinitely.
    % Line 28 forceably breaks us out of the loop if the escape key is
    % pressed.
    
    % Check the state of the keyboard.
    % See if a key is currently pressed on the keyboard. If not, we skip
    % the next for loop from lines 20-38, and basically check again almost
    % immediately.
    
    [ keyIsDown, seconds, keyCode ] = KbCheck;
    
    % If the user is pressing a key,
    % then display its code number and name.
    if keyIsDown
        
        % Note that we use find(keyCode) because keyCode is an array.
        str=['You pressed key ', num2str(find(keyCode)),' which is ', KbName(keyCode), ' typed at time ', ...
            num2str(seconds - startSecs), 'seconds'];
        
        disp(str);
        % Display which key has been pressed.
        
        % If the key that has been pressed is the escape key break out of all loops
        % including the indefinite while loop.
        if keyCode(escapeKey)
            break;
        end
        
        while KbCheck; end
        % If the user holds down a key for more than a microsecond,
        % KbCheck will report multiple events, since computers are faster
        % than people's fingers
        % To condense multiple 'keyDown' events into a single event,
        % once a key has been pressed
        % we wait until all keys have been released
        % before going through the loop again
        
    end
end
ListenChar(0);