The box-shadow around the "payun-payun" header element on https://belen-albeza.github.io/scroll-demos/parallax.html isn't rendered properly. See attachment (from macOS, where it's squished into the top-left). On Windows the box shadow seems missing entirely.

Given the nested transforms it's likely a regression from https://github.com/servo/webrender/pull/3030 or such. I could take a look if nobody's looking at related issues.

Expected: Green rounded rect over red rect of the same size. Actual: Scaled green rounded rect. Forcing each picture to have a surface fixes the position of the green primitive but not of the rounded clip, so I found one of the bogus space conversions but there's more...

So, some notes for myself while I debug this and try to wrap my head around all the coordinate spaces that are at play. In the simplified test-case, all the primitives have the correct dimensions, we're just clipping out extra stuff incorrectly. The render task for the clip mask has the right size and such, and as far as I can tell the uv computation to actually do the clipping in the brush shader is performed in device space so it looks correct to me as well (as in, the bounds for the rounded rect are also right, 100x100 device pixel). The task origin also looks right to me, so my next guess is the clip mask getting incorrectly transformed in the shader, which produces a smaller unclipped area than what it should.

left: non-WR, right: WR At 100% zoom the left and right corners are cut-off. It depends on the zoom level. At 30% zoom the shadow looks crazy, but this page has in general strange bugs, also with non-WR.

Emilio are you still looking at this?

This was fixed by that WR PR, but looks like it has regressed recently again... The page over-all has regressed quite a lot recently. I'll file and take a different bug for that.