[davidp]

Agreed. Pre-Wayland, Linux/X typically needs to treat all your screens as viewports onto a single virtual screen, which of course has to have a single DPI.

This is a more common use case than some folks might imagine. My laptop screen is HiDPI, but as soon as I plug into a projector or screen sharing device that acts as a second display, things get realllllly weird: Linux/X does not know how to dynamically change screen DPI without logout/login. I work around it by just running my laptop screen at "low" DPI. I don't miss it TBH; I suspect that many people who do notice it have better eyesight than me (possibly an age thing).

Wayland is supposed to help with this to some extent, but it's not yet ready for prime time.