I actually added the ability to add a QR code on the map to the renderer backend quite a while ago, but up to now it was only accessible via a command line parameter when starting the renderer directly.
This has now changed, and the web interface now offers a new QR code effects overlay. For now the endoced text is fixed to the request URL of the rendered map itself, but as soon as I’ve finished my plans for allowing for input of extra overlay customization parameters the QR code content will be freely customizeable.
