Created attachment 793 [details]
Screenshot of some graphical glitches produced by clicking in the session
Newer versions of Google Chrome on Android seems to either have a bug in canvas drawing methods or it exposes a bug in Web Access' graphics code. We get dark and ugly areas on and around updated sections of the screen. Very easily reproduced by clicking in the session.
Found using Chrome v57 on Google's Pixel C tablet (Android 7.1.2). Can also reproduce on a Galaxy S6 phone (Android 6.0.1) using the same version of Chrome.
Can reproduce with both 4.8.0 (build 5414) and 4.7.0 (eudemo).
Created attachment 794 [details]
More examples of glitches
Created attachment 795 [details]
This has something to do with Chrome applying sRGB color conversion on some operations. Doing a gamma "correction" of 1/2.2 on the data before feeding it to Chrome makes the problem go away.
However I cannot reproduce the issue with simple test cases, so it's not clear what is triggering it.
I found the trigger. Apparently small canvases are unaffected. Perhaps there's a point where it gets offloaded to the GPU, and that's where things go wrong.
This commit seems like a likely candidate for when things got screwed up:
We will mention this on social media and get a platform specific note up about this. After that we'll wait a short while and see what upstream does.
Seems to be fixed upstream now. Chrome 60 no longer shows the bug. Tested on Pixel C.
It is indeed fixed in later versions of Google Chrome.
Tested on Samsung S8 with Chrome 60 and 61.