function MultiTouchMinimalDemo(dev, screenId, verbose)
% MultiTouchMinimalDemo([dev][, screenId=max][, verbose=0]) - A basic demo for multi-touch touchscreens.
%
% Run it. Pressing the ESCape key will stop it.
%
% Touch the screen and watch the nice colorful happy blobs
% sprinkle to life :)
%
% The demo will try to use the first available touchscreen, or if
% there isn't any touchscreen, the first available touchpad. You
% can also select a specific touch device by passing in its 'dev'
% device handle. Use of touchpads usually needs special configuration.
% See "help TouchInput" for more info.
%
% You can select a specific screen to display on - usually the screenId
% of the touch screen display surface - with the optional 'screenId' parameter,
% or it will select the default maximum screenId if omitted.
%
% If you set the optional 'verbose' flag to 1, then the unique touch
% id and time delta in msecs between touch updates for each touchpoint
% will be printed. This slows the processing down somewhat, as 'DrawText'
% is more slow than most other drawing functions.
%
% This demo currently works on Linux + X11 display system, not on Linux + Wayland.
% It also works on MS-Windows 10 and later.
%
% For background info on capabilities and setup see "help TouchInput".
%
% History:
% 05-Oct-2017 mk Written.
% 03-Aug-2018 mk Only exit demo on ESC key, not on all keys.
% 05-Dec-2020 mk Add screenId selection parameter and max screenId default.
% Setup useful PTB defaults:
PsychDefaultSetup(2);
if nargin < 1
dev = [];
end
if nargin < 2 || isempty(screenId)
screenId = max(Screen('Screens'));
end
if nargin < 3 || isempty(verbose)
verbose = 0;
end
% If no user-specified 'dev' was given, try to auto-select:
if isempty(dev)
% Get first touchscreen:
dev = min(GetTouchDeviceIndices([], 1));
end
if isempty(dev)
% Get first touchpad if no touchscreen found:
dev = min(GetTouchDeviceIndices([], 0));
end
if isempty(dev) || ~ismember(dev, GetTouchDeviceIndices)
fprintf('No touch input device found, or invalid dev given. Bye.\n');
return;
else
fprintf('Touch device properties:\n');
info = GetTouchDeviceInfo(dev);
disp(info);
end
% Open a default onscreen window with black background color and 0-1 color range:
[w, rect] = PsychImaging('OpenWindow', screenId, 0);
% Get maximum supported dot diameter for smooth dots:
[~, maxSmoothPointSize] = Screen('DrawDots', w);
% Select good diameter for touch point blobs, but no more than what 'DrawDots' supports:
baseSize = min(RectWidth(rect) / 20, maxSmoothPointSize);
HideCursor(w);
try
% Create and start touch queue for window and device:
TouchQueueCreate(w, dev);
TouchQueueStart(dev);
% Wait for the go!
KbReleaseWait;
% blobcol tracks active touch points - and dying ones:
blobcol = {};
buttonstate = 0;
blobmin = inf;
% Only ESCape allows to exit the demo:
RestrictKeysForKbCheck(KbName('ESCAPE'));
% Main loop: Run until keypress:
while ~KbCheck
% Process all currently pending touch events:
while TouchEventAvail(dev)
% Process next touch event 'evt':
evt = TouchEventGet(dev, w);
% Touch blob id - Unique in the session at least as
% long as the finger stays on the screen:
id = evt.Keycode;
% Keep the id's low, so we have to iterate over less blobcol slots
% to save computation time:
if isinf(blobmin)
blobmin = id - 1;
end
id = id - blobmin;
if evt.Type == 0
% Not a touch point, but a button press or release on a
% physical (or emulated) button associated with the touch device:
buttonstate = evt.Pressed;
continue;
end
if evt.Type == 1
% Not really a touch point, but movement of the
% simulated mouse cursor, driven by the primary
% touch-point:
Screen('DrawDots', w, [evt.MappedX; evt.MappedY], baseSize, [1,1,1], [], 1, 1);
continue;
end
if evt.Type == 2
% New touch point -> New blob!
blobcol{id}.col = rand(3, 1);
blobcol{id}.mul = 1.0;
blobcol{id}.x = evt.MappedX;
blobcol{id}.y = evt.MappedY;
blobcol{id}.t = evt.Time;
% Track time delta in msecs between touch point updates:
blobcol{id}.dt = 0;
end
if evt.Type == 3
% Moving touch point -> Moving blob!
blobcol{id}.x = evt.MappedX;
blobcol{id}.y = evt.MappedY;
blobcol{id}.dt = ceil((evt.Time - blobcol{id}.t) * 1000);
blobcol{id}.t = evt.Time;
end
if evt.Type == 4
% Touch released - finger taken off the screen -> Dying blob!
blobcol{id}.mul = 0.999;
blobcol{id}.x = evt.MappedX;
blobcol{id}.y = evt.MappedY;
end
if evt.Type == 5
% Lost touch data for some reason:
% Flush screen red for one video refresh cycle.
fprintf('Ooops - Sequence data loss! 3rd party interference or overload?\n');
Screen('FillRect', w, [1 0 0]);
Screen('Flip', w);
Screen('FillRect', w, 0);
continue;
end
end
% Now that all touches for this iteration are processed, repaint screen
% with all live blobs at their new positions, and fade out the dying/orphaned
% blobs:
for i=1:length(blobcol)
if ~isempty(blobcol{i}) && blobcol{i}.mul > 0.1
% Draw it: .mul defines size of the blob:
Screen('DrawDots', w, [blobcol{i}.x, blobcol{i}.y], blobcol{i}.mul * baseSize, blobcol{i}.col, [], 1, 1);
if blobcol{i}.mul < 1
% An orphaned blob with no finger touching anymore, so slowly fade it out:
blobcol{i}.mul = blobcol{i}.mul * 0.95;
else
% An active touch. Print its unique touch id and dT timestamp delta between updates in msecs:
if verbose
Screen('DrawText', w, num2str(i), blobcol{i}.x, blobcol{i}.y, [1 1 0]);
Screen('DrawText', w, num2str(blobcol{i}.dt), blobcol{i}.x, blobcol{i}.y - 100, [1 1 0]);
end
end
else
% Below threshold: Kill the blob:
blobcol{i} = [];
end
end
if buttonstate
Screen('FrameRect', w, [1, 1, 0], [], 5);
end
% Done repainting - Show it:
Screen('Flip', w);
% This little bit here will provoke stimulus onset timing failures on
% Windows if something is not quite right.
if verbose == 2 && IsWin
WaitSecs(0.025);
[~, ~, ~, visualtimingmaybesane] = GetMouse(w)
end
% Next touch processing -> redraw -> flip cycle:
end
TouchQueueStop(dev);
TouchQueueRelease(dev);
RestrictKeysForKbCheck([]);
ShowCursor(w);
sca;
catch
TouchQueueRelease(dev);
RestrictKeysForKbCheck([]);
sca;
psychrethrow(psychlasterror);
end
end