I recently found this topic which helped me a lot by pointing me to the
--scale-from argument. I'm pretty happy with the way I can connect my projector now and have the same content displayed on both devices without any panning or clipping.
But unfortunately I don't know how to switch the setting off again after I disconnected the projector.
In my example I have my laptop screen (LVDS1 in xrandr) with a resolution of 1366x768 and the projector (VGA1) with a 1280x800 resolution. After I connect the projector I use
xrandr --output VGA1 --mode 1280x800 --output LVDS1 --scale-from 1280x800
which is inconvenient but at least logical. But when I disconnect the projector later and want to switch back to only using the laptop screen, I need to do something like
xrandr --output VGA1 --off xrandr --output LVDS1 --scale-from 1366x768 xrandr --fb 1366x768
which I find very inconvenient. Also I don't know of any possibility to find out if there's a scale-from setting currently in action. So my question is: Is there an easier way for this? Since 1366x768 is the preferred resolution for the laptop screen I would have expected one to exist.