How reliable is psychoJS.window._windowAlreadyInFullScreen

Online experiments
1

I want my experiment to end if the participant exits the fullscreen mode. I’m planning to use something like this code at the end or beginning of every routine:

if not win._windowAlreadyInFullScreen:
    # full screen exited, end experiment.
    quitPsychoJS("The experiment is over.", false);

However, I read this in the core Window source code (https://psychopy.github.io/psychojs/core_Window.js.html).

		// (!window.screenTop && !window.screenY) does not work in all browsers on all operating systems (e.g. Chrome on
		// Windows). As far as I can ascertain, as of 2019.08.01 there still does not seem to be a reliable way to
		// test whether the window is already fullscreen.
		// this._windowAlreadyInFullScreen = (!window.screenTop && !window.screenY);

Is it any change as to whether is possible to realiable tell if the web browser window is full screen or not?

2

You could monitor the keyboard for the Escape key Each Frame. Then a single key press would exit full screen and then immediately exit the experiment.

3

Hello,
I have tried implementing your solution wakecarter, but I don’t seem to get it right. I have a piece of code in Each Frame that checks if either Escape or the Up key (for debugging) have been pressed, and if so, changes the variable fullscreen_exited from false to true.

The code works fine for Up key presses (i.e. when I press, fullscreen_exited becomes true). But for Escape, it is as if the first press I make is getting ‘caught’ by the browser without being registered by my code. Fullscreen is exited, but fullscreen_exited stays false. If I then press Esc a second time, it is set to true. I am working on Firefox and with PsychoPy v2021.2.0.

Niclai, if you ended up using wakecarter’s solution, did you run into the same problem, and could you find a solution?