Can't fullscreen, or windows get automatically un-fullscreened, when using fractional scaling

Please tell us what your current scaling settings are.

Please also run these commands on the affected machine:

  lspci -k > lspcik.txt
  journalctl -b0 > journal.txt

and attach the resulting text files here.

Here are the outputs

The behavior of the bug really varies between apps and boots. Now, for example, YouTube fullscreens fine without any glitching of the video or artifacts on the other screen. However Minecraft fullscreened at launch, but with half of the other screen being black. When I tried unfocusing and focusing Minecraft, it would turn both screens black for a second before appearing only maximized and not fullscreened (like experienced before with other games). It won't fullscreen again unless i quit the game and relaunch it.

Status changed to 'Confirmed' because the bug affects multiple users.

https://www.reddit.com/r/Ubuntu/comments/iesevz/fractional_scaling_full_screen_video_causes_this/?utm_source=share&utm_medium=ios_app&utm_name=iossmf

This is my video link which I posted on Reddit, same bug has affected me with i915 driver.

One little note: This isn’t a case when I added upscaled monitor resolution (for me, it is 2160x1440 150% to 2880x1920 200%) config and setting intel to modesetting driver on /etc/X11/xorg.conf.d

There are two options for setting the correct scaling:
1. Using xrandr scaling options, causes tearing and fullscreen inconsistencies
2. Adding new upscaled monitor resolution with xrandr and choosing that

Second options has always worked flawlessly for me, but want to make a warning: second option doesn’t work on between kernel 5.0 and 5.4 (that means it doesn’t work on LTS kernel). They reverted a patch after 5.5, and it works flawlessly. Here’s the trick files that I’ve created: https://github.com/nekr0z/linux-on-huawei-matebook-13-2019#display

I think Ubuntu’s X11 fractional scaling method uses the first one, and that’s indeed buggy.

I am also affected by this really weird bug.
It happens on all applications that are using a fullscreen mode, no matter if in the browser or as a standalone application.
The videos i attached shows the problem when i use youtube.
It first starts normal for about 1 sec, then resizes, makes the second screen black and continues playing in just 1 fourth of the screen.
This is not very usable and extremly annoying.

I use a 4k monitor with 125 % as primary and a FHD monitor as secondary with 100% scaling.

Here the same problem demonstration but just this time i am using gnome videos.
At least this app (native GTK) should work I think...

And the logs that were requested above.
Feel free to ask me if you need something else.
I really hope this gets fixed soon.

Just came across another case, just to keep the ball rolling I'll describe it here. I tried fullscreening HBO Nordic, and it worked for 10 seconds the first time. Then the same thing happened as shown by my gif and laurenz video. After first fullscreen though, fullscreening it again triggers the glitch right away.

Anything new about this here? This is really a big deal for me and the user users too i guess.
Try imagine using you PC without the possibility to display anything in fullscreen mode, not very nice :/

If I can help you debug this further, feel free to ask me.

For me, https://extensions.gnome.org/extension/1873/disable-unredirect-fullscreen-windows/ extension solved the issue.

Amazing, this extension really seems to be doing the trick.
At least playing fullscreen videos in Firefox and Gnome Videos seems to be working again.
But Kodi still doesn't work corrently. There is a huge dark border around the actual Kodi window, as you can see in the picture that I attached.

The Ubuntu wallpaper bottom right is my from my second Full HD monitor, if you are wondering.

Yes disabling fullscreen window "unredirection" should work, and was discussed in the previous bug too (bug 1862081).

Yeah maybe i was a bit too early with my statement.
Everything works great with this extension, except from "real" OpenGl/ Vulkan fullscreen applications.

For example any game (i tested Satisfactory and ROTTR) that i run in fullscreen mode has the problem that the screen is only filled about one quarter with the actual game, the rest is all black or sometimes just flickering stuff.
On the upside, when you really want to play a game like that, it doesn't clip over the second screen anymore like it did with the extension disabled.

I have the same problem with Kodi, that is also a OpenGL application iirc.

I mean you could turn on the extension everytime you start a game/ fullscreen application... But that is really inconvenient.

I can't imagine how so few people have this problem. Is the combination of a HiDPI and FullHD monitor with fractional scaling enabled so rare ...?

Affects me too. Extension helped, thx!

I use 125% Fractional scaling, and if I try to take a screen shot using the app `Shutter`, if the region is almost the full screen, the screen goes wonky and keeps switching resolutions, its impossible to screenshot the area I require. Also VLC can't switch to full screen. Only Chrome successfully can go full screen, all other apps glitch quite badly.

This bug is about Xorg fractional scaling AFAICS.

Starting in Ubuntu 22.04 at least, everyone should be able to use Wayland fractional scaling. If anyone here is using Wayland already then please open a new bug for that.