Mentioned in SAL (#wikimedia-operations) [2019-09-04T11:24:30Z] <Lucas_WMDE> lucaswerkmeister-wmde@mwmaint1002:~$ printf '%s\n' 'https://en.wikipedia.org/static/images/project-logos/wikidatawiki-1.5x.png' | mwscript purgeList.php wikidatawiki # T230120
What about my comment above? The logo noticeably shrinks when going from 140% to 150% zoom (and grows again when going back), I don’t think that should happen. (Tested in Firefox – in Chromium, the closest zoom points are 125% and 150%, which is far enough apart that it’s not as noticeable.)
The logo files themselves seem to be correct – the 1x logo at 200%, the 1.5x logo at 133% (200%/150%) and the 2x logo at 100% look pretty much the same, except that the higher-res versions are less blurry of course. But the stylesheet adds the following rule only to the 1.5x and 2x versions of the logo:
background-size: 135px auto;
I don’t know why that rule is there, but it seems to be the cause for the difference in appearance. If I add it to the 1x logo rule in dev tools, the transition between 140% and 150% looks smooth, at the cost of the logo being smaller than before at 100%.
I think the problem is simply that the Wikidata logo is wider than usual? The 1x PNG is 156px wide, whereas most other logos are 135px. Changing the background-size for the high-res logos to 156px auto also results in consistent scaling, with no change to the 1x logo.
However, the 135px in the CSS are hard-coded in ResourceLoaderSkinModule :/
Edit: kbdwiki, for example, has the opposite problem – their 1x logo is only 113px wide, so the logo appears to grow much larger when going from 140% to 150% zoom.
I did some more digging, and Wikidata is far from the only wiki with this problem – see T232012: Logos that aren’t 135px wide don’t scale correctly at 1.5x and 2x resolutions. Not sure if it makes sense to keep this issue open in that case – what do you think, Lydia?