[css-masking] Add mask-repeat-x/y

[kuoe0]

Latest spec: https://www.w3.org/TR/css-masking/#the-mask-repeat

In this discussion, background-repeat-{x|y} will be added to background-4. There is also already a spec issue on csswg-drafts.

As the counterpart of background, it also makes sense to add mask-repeat-{x|y} to the spec.

[kuoe0]

@birtles How do you think for this?

[svgeesus]

Probably, but note the warning issue in the css backgrounds 4 spec:

This section is still being worked out. The tricky thing is making all the start/end keywords work sanely.

https://drafts.csswg.org/css-backgrounds-4/#background-position-longhands

[dbaron]

I wrote some tests to see if any implementations support these.

[dbaron]

We discussed these at the Seattle face-to-face as described in w3c/csswg-drafts#116 (comment)

[astleychen]

Which suggested mask-repeat-{x|y} won't be speced too ? If it's the case, what's the resolution of this bug ?

[dirkschulze]

Based on w3c/csswg-drafts#116 (comment) those properties should not get added to the spec. @astleychen @kuoe0 are ok with that? Do you think there should be a masking specific CSS WG resolution? Let me know please.

[astleychen]

Yes, it's reasonable to have a consistent design with background-repeat property. There is no need for other resolution. Thanks.