Firefox 58 and odd Imagus Rendering Issue at a Site.
With Imagus enabled, it causes weird CSS rendering delays on some sites (for example, at https://www.mysstie.com/, one I maintain).
Video showing the issue: https://www.youtube.com/watch?v=4hTw2Ubi8QE
This is an easily reproducible issue for the webpages it happens on. For some reason it only affects some pages. Here, it doesn't do it on the Main/Mysstie page but does it on the others, including the Systems Specs page which has almost nothing on it. Also happens with 59 beta. It also happens with a clean profile, just not as bad. Most notable when pressing F5 on the System Specs page: https://www.mysstie.com/systeminfo.shtml
For now, I can just exclude Imagus from being active on the site. Just curious what could be going on these specific pages that make it do that?
Thanks.
Posted Feb 4, 2018, 5:57 AM UTC
I see, however in Nightly it's not noticeable, unless you open the developer tools. So, I assume this is an issue with the browser, and it will be improved in the future. It seem to be related to messaging larger amount of data (the site rules in case of the extension). For example, my developer version currently has 374 rules, but it still uses the legacy addon system, which doesn't have this issue at all. Maybe placebo, but it seems that the pages (on your site) load faster too with it. So, there seems to be an issue with their messaging implementation for webextensions. I also don't understand why it has such an impact on rendering, when messaging happens asynchronously.
Edit: I had an incorrect guess, check out the details.
Well, I guess it's nice to know it was reproduced. For now will just exclude the problematic sites since I don't really need it active on them. Luckily, I've only seen it on a handful of places. I might play around with these webpages to see if coding them differently changes something.
Well, I managed to make it happen on most of the pages where https://www.markheadrick.com/systeminfo.shtml is at. If I simply change my footer include to not load a javascript at the bottom, then these render flashes start happening there as well. I put the script back in so it doesn't happen now.
On the Mysstie site, the pages where it doesn't happen also have Javascripts loading in the page for Twitter widgets and such. So, since most sites are loading Javascripts in them, it doesn't crop up. Bizarre.
Might be partially related to 1404468 - Various websites like GitHub load with flash of unstyled content (FOUC) as well.
https://bugzilla.mozilla.org/show_bug.cgi?id=1437644. You might be able fix this yourself by delaying the clientWidth/clientHeight lookup.
Sounds an easy workaround, will do that.