I regularly use my notebook for teaching, with the full screen shown on the projector. With projectors getting better, I often find the projectors resolution to be higher or different than the ones offered by my LCD screen (in the past I just used 1024x768).
What I now would like to do is use the best resolution of the external display, while having the same content down-scaled on the notebook screen (without panning). Alternatively, if the resolution of the projector is smaller in one dimension, black bars would be ok on the LC display. I don't worry about aliasing artefacts on the LCD as long as the external projector uses the highest quality possible.
For example, I recently had:
LVDS1 connected 1280x800+0+0 1280x800 60.2*+ 50.0 ... VGA1 connected 1280x720+0+0 1280x720 60.0*+ ...
xrandr --output VGA1 --mode 1280x720 --output LVDS1 --mode 1280x800
but then the bottom of a full screen presentation was clipped on the projector. In this case, I would like a black bar or vertical rescaling on the laptop screen. How can I achieve that?
I played with the scale option (can't reproduce this here without projector) but was unsuccessful.
How can I achieve this behaviour?