1561283 - [css-grid] Grandchild of grid container doesn't immediately become grid item when its parent gets "display:contents"

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, defect, P3)

Description

[Oriol Brufau [:Oriol]]

Attachment: grid-display-contents.htm

What steps will reproduce the problem?

1. Create a grid container with a child and a grandchild
2. Set display: inline to the grandchild
3. Force a style change event
4. Set display: contents to the child

What is the expected result?
The grandchild becomes a grid item and is blockified

What happens instead?
The grandchild doesn't immediately become a grid item

In the attached testcase, the console should say

#test should be inline: inline
#wrapper should be contents: contents
#test should be blockified (immediately): block
#test should be blockified (after a while): block

The penultimate check fails in Firefox. This seems against https://drafts.csswg.org/css-transitions-1/#style-change-event

implementations must not use, present, or display something resulting from the CSS cascading, value computation, and inheritance process [CSS3CASCADE] without updating the computed value [...]. However, when an implementation updates the computed value of a property on an element to reflect one of these changes, [...] it must update the computed value for all properties and elements to reflect all of these changes at the same time (or at least it must be undetectable that it was done at a different time).

Chromium fails the two last checks: https://bugs.chromium.org/p/chromium/issues/detail?id=978419

Comment 1

[Emilio Cobos Álvarez [:emilio]]

I see what's going wrong. Last one fails as well on a clean profile btw, do you have any extension installed that could cause a restyle on load?

Comment 2

[Emilio Cobos Álvarez [:emilio]]

Attachment: Bug 1561283 - Don't optimize out recascading of children when becoming or stopping being display: contents. r=mats

Since they can change whether descendants get blockified.

Comment 3

[Oriol Brufau [:Oriol]]

(In reply to Emilio Cobos Álvarez (:emilio) from comment #1)

I see what's going wrong. Last one fails as well on a clean profile btw, do you have any extension installed that could cause a restyle on load?

Oh, true. It's caused by uBlock Origin

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/4167fd17006c
Don't optimize out recascading of children when becoming or stopping being display: contents. r=dholbert

Comment 5

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/4167fd17006c

Comment 6

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/17705 for changes under testing/web-platform/tests

Comment 7

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Upstream PR merged