How Do I Set HiDPI Scaling for individual displays on elementary OS Loki?

Question

There have been a lot of questions that are similar in nature, but none can truly address the Issues I've been having. I have a Dell XPS 15 9550 and have pretty much all of the hardware on it supported by manually upgrading the kernel. Yay!

My laptop has a 15 inch 4K display and elementary OS handles it quite well by automatically scaling up everything in Pantheon Desktop. However, it falls short when working with external displays. Any external display that I connect will inherit the same HiDPI setting that my laptop display uses. This means that windowed programs like system settings are scaled up and consume nearly the entire screen of a 27 inch 1440p display.

I would like to keep the HiDPI settings on my laptop screen but then have a different HiDPI setting on my external displays. I want to make better use of the screen's real estate for my work.

Through my research, I have found that I can use xrandr to modify the HiDPI Settings on my screens and I have found what I think is an ideal configuration to solve my problem.

xrandr --output HDMI1 --scale 2x2 --mode 2560x1440 --fb 5120x3600 --pos 0x0
xrandr --output eDP1 --scale 1x1 --pos 600x3600

But it only works momentarily, then something happens in either the nouveau video driver that elementary OS uses by default, or with Pantheon Desktop. The screen goes black, I see some terminal output on my laptop, then the elementary OS login prompt appears and when I login, all my applications that were previously open are closed. Most importantly, all of the changes I made to the displays through xrandr have been reverted back to how it was to begin with.

I would like to be able to adjust the scaling settings of my displays with out my system becoming unstable. My plans are to eventually write a bash script that will configure my displays for me. But right now something is making my early attempts fail. Does anyone have any ideas on how I can change the scale settings on individual monitors in elementary OS?

Answer 1

This isn't really a complete answer, and is probably less of a manual solution, but I'm hoping we can use Pop!_OS new solution in some way... I understand this is done by the system76-hidpi-daemon which is part of the system76-driver Install instructions: http://support.system76.com/articles/system76-driver/

I, however, have no idea if it's a good idea to install the driver on a non System76 computer. I'd prefer to, in some way, only run the hidpi deamon.

More information from their blog:

Our engineer, David has been working on improving HiDPI. While others in the desktop community are focused on Wayland, David has been working on improving HiDPI experience on X, especially if you have an Nvidia video card. When completed, you’ll be able to have a uniform experience when connecting low DPI monitors into HiDPI enabled laptops in the X session. What does that mean? It means that when you plug in your monitor the right thing will happen. We are planning a rolling implementation, meaning that we would introduce these features over time. We hope to show progress on this feature over the next few weeks. So watch this space.

http://blog.system76.com/post/167099907368/popos-development-re-org-upstream-cooperation

Last week, I talked about HiDPI multimonitor work that was in progress. I’m happy to report that, we have made progress. Both NVIDIA and Intel laptops with HiDPI screens can now automatically configure mixed-dpi multi-monitor setups within Pop!_OS. The work needs further testing and refinement before it’s ready to distribute to customers. Going forward, we plan to deliver a seamless multi-monitor HiDPI experience tailored to the different capabilities of Intel and NVIDIA graphics in Pop!_OS.

http://blog.system76.com/post/167349126968/hidpi-extravaganza-putting-the-lid-on-hardware

The work on HiDPI nears completion. The HiDPI work is a seminal project that we are extremely proud of as a company. When this work is complete, you will be able to have smooth experience with multiple monitors of different resolutions and have it do the right thing. Right now, a lot of work is in testing, handling corner cases, and focusing on the little details that build together into a great experience that just works!

http://blog.system76.com/post/168094703848/ux-updates-and-hidpi-aww-yeah

My post on this on Reddit: https://www.reddit.com/r/elementaryos/comments/7c7x8x/pop_os_mixeddpi_multimonitor_setup_on_elementaryos/

Update:

We are currently working on adding GSettings and a DBus API to allow other distros to create their own graphical interfaces to the daemon. The HiDPI daemon, which is currently part of the System76 driver, will become its own package and move into Pop!_OS proper. That means anyone who runs Pop!_OS will be able to use the HiDPI daemon as opposed to just System76 customers.

http://blog.system76.com/post/171934557903/popos-1804-testing-iso-coming-soon-updates-on

Answer 2

maybe you can save your config as shell script with arand I would try this first because it should work with the Nouveau driver.

I normally use the nvidia-binary drivers and configure my screen with th nvidia-settings tool look here for infos about the drivers:

ubuntu nvidia-binary-drivers

Theres an official PPA for binary nvidia drivers xou can install it with:

sudo apt-get install software-properties-common
sudo add-apt-repository ppa:graphics-drivers/ppa
sudo apt-get update

After you switched to the proprietary drivers you can install the nvidia-settings tool with:

sudo apt-get install nvidia-settings

With this tool you can manage all monitor settings and save them.