Resizing XWayland & X11 windows is extremely slow

[Alexander Koskovich]

[ Impact ]

When resizing X11 windows that use server-size-decorations on Xorg or through XWayland (Discord, Spotify, etc) the resize does not take effect until seconds after holding the resize. If you let go of the resize before it happens then window does not resize at all.

[ Test Plan A ]

1. Enable fractional scaling and set a scaling factor of 125% or 150%
2. Log into an Ubuntu Desktop Wayland session
3. Start Spotify
4. Try to resize the window
5. Verify that the window can be resized normally

[ Test Plan B ]

1. Enable fractional scaling and set a scaling factor of 125% or 150%
2. Log into an Ubuntu Desktop Xorg session
3. Start Spotify
4. Try to resize the window
5. Verify that the window can be resized normally

[ Where problems could occur ]

This update is included in the 4.18.5 bugfix release from upstream. See bug 2109964

[ Other info ]

The issue was originally reported on NVIDIA hardware:
"""
Ubuntu 25.04 Beta
NVIDIA RTX 5090 (570.133.07)
"""
but it can be reproduced on any graphics driver.

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Libera.chat.

To change the source package that this bug is filed about visit https://bugs.launchpad.net/ubuntu/+bug/2107245/+editstatus and add the package name in the text box next to the word Package.

[This is an automated message. I apologize if it reached you inappropriately; please just reply to this message indicating so.]

[Alessandro Astone (aleasto)]

I can reproduce on non-NVIDIA.
Do you use fractional scaling by any chance?

> XWayland & X11 windows
What does that mean exactly? You can reproduce by resizing any window on an Xorg session?

[Alexander Koskovich (nexusprism)]

> Do you use fractional scaling by any chance?
Yes, 150%

> You can reproduce by resizing any window on an Xorg session?
Did some further testing, and I can't reproduce the issue with apps like Chrome or Ptyxis, but I can with Discord, Telegram, and Spotify. Only when they are inside an Xorg session or running under XWayland, if I force them to run as Wayland they are fine.

I turned off fractional scaling, and resizing is fine.

[Daniel van Vugt (vanvugt)]

Can you open a Terminal window and leave 'top' running before reproducing the bug? I'm wondering if any process (like mutter-x11-frames, gnome-shell or the app itself) is requiring too much CPU.

[Daniel van Vugt (vanvugt)]

See also https://gitlab.gnome.org/GNOME/mutter/-/issues/4061

[Alexander Koskovich (nexusprism)]

Is it possible to patch the GTK package to include https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/8459 while we wait for a new GTK release to come out?

[Alessandro Astone (aleasto)]

I can confirm that https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/8459 fixes the issue for me

[zz luz (myth5)]

sorry,i make a mistake.i don't know why i can change this status.