>Psychtoolbox>PsychDemos

MultiTouchPinchDemo([dev][, screenId=max][, debug=0]) - A basic demo for multi-touch touchscreens.

Run it. Pressing the ESCape key, or comleting ten demo trials will stop it.

This shows implementation of simple code for “two finger pinch” detection.
The demo draws a line segment at random location and expects the user to put
to finger on the touch screen to “squeeze” the line segment between their finger.
It will complete a trial if both fingers are moved close enough and the line
segment is between both fingers.

Motivated by the line-intersection task from:
https://psychtoolbox.discourse.group/t/help-with-multitouch/4953

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.

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”.