1291187 - getComputedStyle() of "flex-basis" should return "10%" if the style sets to "calc(0px + 10%)"

Status: RESOLVED FIXED

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

Description

[Daisuke Akatsuka (:daisuke)]

Attachment: getComputedStyle.html

I attach the test html.
For now, that returns "calc(0px + 10%)".

Comment 1

[Brian Birtles (:birtles, Feb 26~ parental leave)]

Just a few notes, the spec doesn't actually say this but this is what Chrome does and it seems sensible to spec.

At the moment we seem to do:

calc(300px + 0%) -> 300px
BUT
calc(0px + 10%) -> calc(0px + 10%)

I'm not sure what the reasoning for this is (I looked up the changeset and bug and there was no explanation) but it seems like we should either always simplify or never.

Comment 2

[Brian Birtles (:birtles, Feb 26~ parental leave)]

(In reply to Brian Birtles (:birtles) from comment #1)
> Just a few notes, the spec doesn't actually say this but this is what Chrome
> does and it seems sensible to spec.
> 
> At the moment we seem to do:
> 
> calc(300px + 0%) -> 300px
> BUT
> calc(0px + 10%) -> calc(0px + 10%)

There is actually some spec text for this[1] although it as marked as being "under discussion".

As it currently stands it would suggest we preserve zero values so that, `the calc() doesn’t suddenly "change shape" in the middle of a transition when one of the values happens to have a zero value temporarily.'

I don't really understand the concern there but in any case, Gecko's behavior doesn't match that either so something will need to change here.

[1] https://drafts.csswg.org/css-values/#calc-serialize

Comment 3

[Boris Chiou [:boris]]

This bug should have been fixed, per the spec issue. However, it'd be better to add some tests in wpt.

Comment 4

[Boris Chiou [:boris]]

Attachment: Bug 1291187 - Add tests for testing the computed values of flex-basis.

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/a5d8c96d2eb7
Add tests for testing the computed values of flex-basis. r=emilio

Comment 6

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

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/18129 for changes under testing/web-platform/tests

Comment 7

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

Upstream web-platform-tests status checks passed, PR will merge once commit reaches central.

Comment 8

[Raul Gurzau (:RaulG)]

https://hg.mozilla.org/mozilla-central/rev/a5d8c96d2eb7

Comment 9

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

Upstream PR merged