How to test a GTK Merge Request patch (MR 7909) on Fedora?

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1

Hi everyone,

I’m currently trying to solve an issue with my Wacom CTH-470 tablet on Fedora 42 using Wayland. Specifically, when I use the pen, the cursor disappears and doesn’t come back when I lift the stylus off the tablet surface. I’ve been troubleshooting this issue by following this GTK issue thread (#6312), and I eventually found Merge Request 7909, which seems to propose a fix.

From what I understand, the problem seems related to the cursor hiding logic not updating properly with stylus movement events. The patch modifies gtk_text_view_unobscure_mouse_cursor() to skip or adjust a timestamp check that might be preventing the cursor from reappearing.

The issue appeared after I switched from OpenTabletDriver back to Fedora’s default drivers, and forced the system to use the Xorg Wacom driver instead of the libinput one, since it seems to be more up-to-date and provides better options in the graphical settings panel
The issue seems to be linked to AMD GPUs using Mesa under Wayland. Mesa already gave me some headaches back on Fedora 40. When I first tried using Wayland, I ran into several issues—likely related to Mesa—so I switched to Xorg, and everything worked fine. But now that Wayland is the only supported option on Fedora 42, I don’t have another option than trying to fix the current bug. Anyways, things seem to have improved a lot, and Mesa no longer causes the problems it used to. I really appreciate the amazing work from everyone involved in fixing these kinds of bugs—I hope one day I can give back to the community that’s made such a stable and polished distro. Honestly, I’d already have thrown Windows in the trash if it weren’t for the fact that I’m still learning After Effects there. Unfortunately, this new cursor bug with the tablet stylus has popped up, just when everything else was running smoothly. I really wish I could just swap out my AMD GPU to avoid these random Mesa-related issues altogether :sweat_smile:

The thing is… I’m pretty new to this :sweat_smile: and I have no idea how to test a GTK patch locally on Fedora without messing up my system. I’ve already cloned the GTK repository, but I got stuck on what to do next, I’m not sure what the right way is to apply or build a patch from a GitLab MR.

So here are my questions:

  1. How do I apply a patch from a GitLab Merge Request like this (MR 7909)?
  2. What’s the best way to build and test it locally?
  3. Is there a recommended way to test GTK changes on Fedora specifically, or a safer workflow I should follow?

Any help or guidance would be hugely appreciated. Thanks in advance!

2

It should be already in F42:

A more generic approach for unmerged patches:

  • Clone the repo from src.fedoraproject.org.
  • Add the patch and update the specfile.
  • Build and install the RPM package.

Note that the scope for each patch is limited.
It’s often not realistic to backport the changes.
Fedora Rawhide may be necessary for testing.
You can deploy a VM or container for this task.

3

So, if it’s already merged into Fedora 42, does that mean my bug might be fixed in a different way? I’m not sure what else to try — any suggestions?

4

Make sure your system is fully upgraded:

> rpm -q gtk4 
gtk4-4.18.4-1.fc42.x86_64

If the problem persists, consider to open an issue upstream.

5

Yes, everything is up to date. I upgraded to Fedora 42 just a few days ago. Where should I report this issue upstream? I submitted it on Bugzilla, but I’m not sure if that was the right place — I’ve never had to report a bug like this before.

Right now, I only have two options: using OpenTabletDriver or the default Wacom drivers for Wayland on Fedora 42. With OpenTabletDriver, the pen works great, but touch gestures don’t work properly. On the other hand, with the Wacom drivers, touch gestures work fine, but the pen doesn’t behave correctly.

6

Your original question was about applying and testing patches, which was hopefully answered, but I’m not familiar with the software stack supporting that hardware part.
It may be worth opening a new topic focused on the hardware and driver aspects.

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7

Thank you! Yes, your response about applying and testing patches was really helpful — I appreciate it. Since the issue seems to be more related to the hardware and driver side, I’ll go ahead and open a new topic focused on that. Hopefully, someone more familiar with the Wacom stack on Fedora can give me a hand there. Thanks again for pointing me in the right direction!

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