[X2Go-User] Worse image quality after upgrading Firefox to 52 ESR

[south0 at tuta.io]

Hi,

after upgrading Firefox form v45 ESR to v52 ESR, the image quality in the X2Go client dropped considerably. Using the same setup in both cases, I now see "blocks" of JPEG artifacts scattered around the window.

My setup:

- Ubuntu 16.04 LTS i686
- X2Go server from stable PPA
- X2Go Qt client in Windows (tested in 7 and 10)
- nx set to link=lan, pack=adaptive-9, the rest as default
- Firefox from Mozilla's builds (https://ftp.mozilla.org/pub/firefox/releases)

I'm untaring Firefox to a dedicated dir and pointing X2Go to execute it. The tests were made with fresh Firefox profiles in both cases, with HW acceleration disabled and rendering by cairo. A major difference is that Firefox 45 uses GTK2 while Firefox 52 uses GTK3.

The areas with artifacts seem to be placed randomly. Icons next to each other in the chrome may or may not be affected. Multiline paragraphs are sometimes divided across the upper/lower middle of the characters.

If I highlight text around quickly, or zoom in/out, I can make the artifact blocks "jump" to other areas in the viewport. After tweaking the font configs, I managed to get rid of the artifacts consistently in text-only documents by using an aliased font against a solid background. Artifacts in the chrome remain nevertheless.

If I set the nx pack to rle for instance, the artifacts disappear. I'd still like to know if

- this is a bug or expected behaviour
- I can still use adaptive-9 while getting a constant/reproducible image quality

Let me know if you need more info or sceenshots. Thanks in advance.


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