4K issues with window content

[okias]

Laptop: XPS 9350, 4K 3200x1800, Intel GPU 620.
Software: Mutter + GNOME Shell 3.36.4
Servo: 2020-08-06 tarball Linux x64
Session: Wayland

Application first run:

Resize to half-screen:

Fullscreen resize:

Reproducible all the time.

[Craig-Macomber]

Building latest master (ab5c241), I was unable to reproduce this on my Ubuntu on Wayland setup (20.04) using my 4k (3840*2160), GNOME Shell 3.36.4. I also had no issues at larger sizes (via multi monitor).

Then I tried with UI scaling (I normally run at 100% scale, despite my 4k screens), and I got rendering errors similar to described here at 200% scaling, and crashes and rendering errors when at 300%.

When at 200% scaling:

Edit: I should add that this is not strictly a rendering bug. All the links/buttons click where they appear to be, so its general UI scaling, not strictly visual issue.

Edit again:
After some more testing, this seems to manifest when the UI scaling changes, ex: dragging from a monitor with one scale setting to another with a different scale. Changing the scale factor for the monitor its on doesn't break it, but does cause dragging it onto another monitor and back to break it. Seems like maybe there are two scale factors being tracked (one for the title bad and one for the content) and one of them has an invalidation bug letting it get out of sync? This might be a different but than the one being tracked by this thread.

[paulrouget]

After some more testing, this seems to manifest when the UI scaling changes

We don't support live DPI changes. You need to restart.

For wayland specific issues, we need to figure out if it's a winit/glutin problem or a servo issue.

[Craig-Macomber]

@paulrouget I was able to produce the same issue I reported above in a an unrelated rust application which uses winit (one of my own projects), so I do not think the issue I reported is a servo issue.

[resynth1943]

Huh. This also happens to me while using searX. Perhaps it's a Rust issue?

[paulrouget]

Likely winit on wayland.