Managing Non-HiDPI monitor with Dell XPS 9370

Does anyone have a good setup for connecting the 9370 to a non-HiDPI external monitor and keeping both monitors usable? At my desk at work, I -only- use the external monitor (I dock the 9370 to a TB16 and keep the laptop closed and use my Apple Thunderbolt monitor only) and this works fine. However, I've been struggling to create a workable solution for our meeting rooms where I plug in via HDMI to a flat panel TV (so, 1080p 50" or so) and want to be able to use it either in mirrored or 2nd screen mode. Either the content on the TV is enormous or the content on the laptop screen is unusably tiny, depending on how I set the scaling.

I understand the root problem is that X11 does not support per-screen scaling factors. I had hoped Wayland would be the answer, but the problem there is that while Wayland itself supports per-screen scaling, most apps don't support Wayland so they fallback to Xwayland, and Xwayland does not support per-screen scaling.

One idea I had is that rather than keeping the laptop at native 3840x2160 resolution with a 2x scaling factor in the OS, I've just set the laptop's resolution to 1920x1080 (half-native) with 1x scaling, thinking that then when I connected the external monitor the DPI difference between the two wouldn't be so stark and they could work at the same scale. However, when I connect a conference room display to the HDMI, for some reason Linux reverts the laptop screen back to full-native resolution again and then I once again have the problem of either huge content on TV or tiny content on laptop. And I can't seem to change the resolution in the Gnome display settings (there's literally no Apply button after I pick a different resolution). When I unplug the external monitor, the laptop goes back to 1920x1080.

So, I'm kind of stuck. Is there something else that I could try that might make this workable?

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2 Replies

Re: Managing Non-HiDPI monitor with Dell XPS 9370

I have some tips, but not sure if they're helpful!

I also just switch my main resolution back to 1920x1080 and I'm not having any issues with this. Maybe you can try switching back to X (or to Wayland, depending on what you were using). Really weird that you're not seeing an apply button. Are you sure it's not simply outside of reach because of the blown up interfaces?

Another solution is to just keep all the scaling to 1X and try to deal with that. This will be fine for your external screen, but a bit clumsy for your laptop screen. However, you can make your external your 'main' and just blow up things as much as you can on the laptop screen.

For example, I often have a browser or terminal open on my laptop screen, and those make it super easy to just increase the font.

I heard that it is possible to get mixed resolutions with wayland, and I got this to work once. It involves tinkering on the command line because the UI's are just not ready.

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Re: Managing Non-HiDPI monitor with Dell XPS 9370

Thanks for the reply! I did notice this week that when I plug into _some_ of the TVs in my office conference rooms, the laptop screen stays at 1920x1080, whereas with other TVs when I plug in the laptop screen reverts to 3840x2160. Not sure what that's about, but if the laptop screen stays at 1920x1080, the setup is workable. Also, if I mirror the screens instead of using the TV as a second screen, then it also is kinda workable (although I don't like working that way, I prefer to keep the TV as a separate presentation screen and then be able to do work "off to the side" on the laptop - works better for our typical meeting workflows). 

As for Wayland, I -did- get two different scaling factors on the two screens, that part worked fine (I partitioned my drive and installed Arch Linux to test it). And if you use a Wayland-enabled app, like say the terminal, when you drag it between screens it auto-adjusts the scale, and it's great. Unfortunately, very few apps are Wayland-enabled. In that case, the system wraps the app in Xwayland, which because it's relying on X does not honor the per-device scaling. 

I think if I try to use the rooms with the TVs that behave better as much as possible, and mirror when I'm in other situations, I'll get by. I just wish the overall support for HiDPI in Linux was a little farther along than it is. Maybe this'll all be easier in a year or two.

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