I'm creating a QrCode-based electronic point system and I ended up crashing because I can not focus on QrCode when I'm on a mobile phone for example. I say this because on the webcam there is the possibility of focusing far or near by turning the screen of it, in the mobile I need to do this via software.
I'm using the Ciro Costa's QCodeDecode API that uses html5 and I believe it uses getUserMedia for the stream: link
But I did not find anything to change the focus of the camera as javascript ...
I think it's not impossible, there are QrCode reader apps that do the autofocus with the android camera.