[Bug]: fractional scaling font blurriness on 0.7

[alexreid]

Describe the bug

When using a 125% fractional scaling factor on Gnome, Tuba 0.7.1 has rendering issues and blurry text compared to Tuba 0.6.3.

Steps To Reproduce

1. Install Tuba 0.7.1
2. Set display scale to 125% in Gnome Settings (you may need to enable this via gsettings set org.gnome.mutter experimental-features "['scale-monitor-framebuffer']" depending on distro)
3. Open Tuba
4. Note that text looks blurrier, and scrolling can produce strange graphical artefacts

Logs and/or Screenshots

0.6.3:

0.7.1:

Instance Backend

Mastodon

Operating System

Fedora Workstation 39, Gnome Shell 45.5, Wayland session

Package

Flatpak

Troubleshooting information

os: GNOME 46 (Flatpak runtime)
prefix: /app
flatpak: true
version: 0.7.1 (production)
gtk: 4.14.1 (4.14.1)
libadwaita: 1.5.0 (1.5.0)
libsoup: 3.4.4 (3.4.4)
libgtksourceview: 5.12.0 (5.12.0)

Troubleshooting info from 0.6.3, installed from Fedora Flatpak repo

``` os: Fedora Linux 39 (Thirty Nine) prefix: /app flatpak: true version: 0.6.3 (production) gtk: 4.12.5 (4.12.5) libadwaita: 1.4.3 (1.4.3) libsoup: 3.4.4 (3.4.4) libgtksourceview: 5.10.0 (5.10.0) ```

Additional Context

No response

[GeopJr]

Thanks for the report!

Could you try GSK_RENDERER=ngl flatpak run dev.geopjr.Tuba and tell me? I see some blurriness here but it's far less noticeable than on your screenshot

The GTK version shipped with GNOME 46 changed renderers and made ngl the default. Due to performance not being on par with gl, some apps including Tuba, set it back to gl until everything gets ironed out. I'm afraid this might be a regression on the GTK side of things

[alexreid]

It does seem to look slighly better with the ngl renderer:

I'd say it's not quite as good as 0.6.3, but sits perhaps somewhere in the middle. I haven't spotted any weird rendering artefacts yet with the ngl renderer, although I've only tested briefly so far.

[GeopJr]

After reading some issues on gtk's tracker, could you try GDK_DEBUG=gl-no-fractional (without setting the renderer to ngl). It looked clear to me with that on!

Otherwise, you can also give vulkan a try GSK_RENDERER=vulkan flatpak run dev.geopjr.Tuba

[alexreid]

Thanks for looking into it! With GDK_DEBUG=gl-no-fractional it looks identical to 0.6.3, to my eye, at least:

The Vulkan renderer also looks good (although performance takes a hit on my machine):

[GeopJr]

Thanks for confirming, I'll set gl-no-fractional automatically on the next patch release!