Bug 271714 – [GTK] Blurriness with fractional scaling

• Status: NEW
• Component: WebKitGTK

Created attachment 470608 [details]
The GUI and sidebar headlines should be crisp, while the article content is blurry.

Content text (and maybe images) is blurry in GNOME Web and Newsflash, no matter the font setting, and using my trackpad gestures to zoom out after zooming in causes a freeze and "WebKitWebProcess" crash. The RedHat crash reporting app does not manage to properly record and report the crash. This is a fairly new development; WebKitGTK has worked until recently, but I couldn't tell you how recently. I will attach a screenshot with the blurry text, but my screen has an odd aspect ratio and resolution, you might have trouble noticing it. In the screenshot, the GUI and sidebar headlines should be crisp, while the article content is blurry.

I am using Fedora 39 Workstation (GNOME 45.5) with Wayland.

# System Details Report
---

## Report details
- **Date generated:**                              2024-03-26 12:50:23

## Hardware Information:
- **Hardware Model:**                              Framework Laptop _12th Gen Intel Core_
- **Memory:**                                      16.0 GiB
- **Processor:**                                   12th Gen Intel® Core™ i5-1240P × 16
- **Graphics:**                                    Intel® Graphics (ADL GT2)
- **Disk Capacity:**                               250.1 GB

## Software Information:
- **Firmware Version:**                            03.04
- **OS Name:**                                     Fedora Linux 39 (Workstation Edition)
- **OS Build:**                                    (null)
- **OS Type:**                                     64-bit
- **GNOME Version:**                               45.5
- **Windowing System:**                            Wayland
- **Kernel Version:**                              Linux 6.7.9-200.fc39.x86_64

I am using 125% Fractional Scaling.

I might be wrong about the blurriness only affecting content views. I think it also affects the interfaces of NewsFlash and GNOME Web, even though other GTK4 apps are not blurry.

[Michael Catanzaro]

That Newsflash screenshot looks perfectly fine to me, so I'm guessing it is indeed related to your screen. You'll want to edit the title of this bug to describe the problem; nobody is likely to look at the bug if it doesn't have a title.

Then the crash is surely bug #266875.

(In reply to Michael Catanzaro from comment #3)
> That Newsflash screenshot looks perfectly fine to me, so I'm guessing it is
> indeed related to your screen. You'll want to edit the title of this bug to
> describe the problem; nobody is likely to look at the bug if it doesn't have
> a title.
> 
> Then the crash is surely bug #266875.

(In reply to Michael Catanzaro from comment #3)
> That Newsflash screenshot looks perfectly fine to me, so I'm guessing it is
> indeed related to your screen. You'll want to edit the title of this bug to
> describe the problem; nobody is likely to look at the bug if it doesn't have
> a title.
> 
> Then the crash is surely bug #266875.

First comment was a mistake; couldn't find edit button. As for the title, thanks for catching it!

Finally, when I said it was related to my screen, I meant it was related to the hidpi fractional scaling, not a phyisical default or driver issue with my screen. As I said, it occurs in no non WebKitGTK apps (except with unrelated issues like xwayland), so I am pretty confident there is a bug with WebKitGTK. I might be able to attach a comparison screenshot so the relative fuzziness is visible.

[Michael Catanzaro]

Only one problem per bug please. Let's use bug #266875 to track the problem with touchpad zooming.

Understood. With this update, I realize these are unlinked.
The culprit is the GNOME 46 Flatpak runtime. GNOME Web and Newsflash are affected, but installing Foliate from my distro's repo and Wike from Flatpak, which have not been updated, the issue does not occur.

The Matrix chat informs me that GNOME 46 updated to GTK 4.14, which introduces native fractional scaling (as opposed to the previous upscaling solution). This blurriness only affects webkitgtk apps, however, which suggests the problem lies in the way it deals with the new fractional scaling method.

Quote from user kepstin: "(either epiphany or webkitgtk have to apply some workarounds to figure out how the widget is misaligned from the pixel grid, and then compensate for that when rendering the contents to bring things back into alignment)"

They also linked to this: https://gitlab.gnome.org/GNOME/gtk/-/issues/6381

I am also attaching another screenshot to provide a better comparison, but due to my screen's resolution, you may need to a good image viewer and zoom in to notice the difference.

Created attachment 470642 [details]
Comparison of Wikipedia page for Lorem Ipsum running in Firefox vs Epiphany. Both text and images in the main window are blurrier.

[Patrick Griffis]

I tested passing the correct scaling all the way through it still comes out blurry.

The Tuba Mastodon client does not, to my knowledge, use webkitGTK, but it seems to have had a similar issue. This commit fixed it: https://github.com/GeopJr/Tuba/commit/594dc605484a4f0266b3d2618ef0f6e9a6d69459

Trying GDK_DEBUG=gl-no-fractional flatpak run org.gnome.Epiphany, the result seemed less blurry than flatpak run org.gnome.Epiphany, but I can't compare with pre-regression 45 until I can run it in a VM, if ever.

I think this bug may be misreported. There seems to be some blurriness not just with my WebkitGTK apps but other, if not all, Flatpaks running the GNOME 46 runtime. Crispness is restored with GDK_DEBUG=gl-no-fractional. But don't remove this bug yet unless it can be confirmed; the fact I noticed this much earlier with webkitgtk may indicate this is a separate issue.

[Michael Catanzaro]

*** Bug 276418 has been marked as a duplicate of this bug. ***

[David Keller]

Pull request: https://github.com/WebKit/WebKit/pull/34556