Remove `overrides_transform_style()` and `get_used_transform_style()` by mrobinson · Pull Request #388 · servo/stylo

mrobinson · 2026-06-12T21:18:04Z

It's not possible to properly calculate these only looking at style,
because the results depends on the used overflow value.

Servo PR: servo/servo#45629

Loirooriol · 2026-06-12T21:36:55Z

+        !matches!(self.get_box().clone_overflow_x(), Overflow::Visible | Overflow::Clip) ||
+            !matches!(self.get_box().clone_overflow_y(), Overflow::Visible | Overflow::Clip) ||


Should this check the used overflow? E.g. a table row is a transformable element so transform-style applies, but overflow doesn't. Or propagation of overflow to the viewport.

If so, this should move to Servo. May make sense to move it regardless.

Good point. I've modified this PR to simply remove this functionality, have moved it to servo/servo#45629, and ensured that there the used overflow is considered when determining the used TransformStyle.

Seems you didn't push the removal?

This was the typical situation where I had this in my working directory, but uncommitted. I've pushed it now.

Stylo was using a very incomplete method for calculating the used `TransformStyle` for boxes, which didn't incorporate all of the grouping properties from the specification. This change moves the functionality into Servo (as cannot properly compute this value without `FragmentFlags`) and makes it more complete. We still do not process the value of `contain`, `mask-iamge`, and `mask-boarder-source` as we do not support those values yet. Incidentally, this also fixes a panic that we were causing in WebRender, probably by going down a path that Gecko does not exercise. Stylo PR: servo/stylo#388 Signed-off-by: Martin Robinson <martin@abandonedwig.info>

nicoburns · 2026-06-14T16:04:21Z

One thing I've thought about for these kind of values is that it could be useful to pre-compute the bits that can be computed purely from style information and store them on the ComputedValues/ComputedValuesInner in a bitset (I am imagining that this would be a bit of Servo-only code that runs during the style pass as/just after the computed values for a node are computed). That would make it much cheaper to check rather than doing comparisons on several style properties each time (some of which like the transforms can be quite large).

Not sure how much different it would make to performance, but it'd be an easy optimization to implement, and might also be quite nice in terms of "making the code structure reflect the spec"?

mrobinson · 2026-06-14T16:15:11Z

Not sure how much different it would make to performance, but it'd be an easy optimization to implement, and might also be quite nice in terms of "making the code structure reflect the spec"?

That's an interesting idea. I think our plan in Servo is to cache these kinds of things on the Fragment, but maybe there is room for multiple layers of caching.

It's not possible to properly calculate these only looking at style, because the results depends on the used `overflow` value. Signed-off-by: Martin Robinson <martin@abandonedwig.info>

Stylo was using a very incomplete method for calculating the used `TransformStyle` for boxes, which didn't incorporate all of the grouping properties from the specification. This change moves the functionality into Servo (as cannot properly compute this value without `FragmentFlags`) and makes it more complete. We still do not process the value of `contain`, `mask-iamge`, and `mask-boarder-source` as we do not support those values yet. Incidentally, this also fixes a panic that we were causing in WebRender, probably by going down a path that Gecko does not exercise. Stylo PR: servo/stylo#388 Signed-off-by: Martin Robinson <martin@abandonedwig.info>

servo#45629) Stylo was using a very incomplete method for calculating the used `TransformStyle` for boxes, which didn't incorporate all of the grouping properties from the specification. This change moves the functionality into Servo (as cannot properly compute this value without `FragmentFlags`) and makes it more complete. We still do not process the value of `contain`, `mask-image`, and `mask-border-source` as we do not support those values yet. Incidentally, this also fixes a panic that we were causing in WebRender, probably by going down a path that Gecko does not exercise. Stylo PR: servo/stylo#388 Testing: This adds a new crashtest. Three other WPT tests start to pass. Fixes: servo#42476. Signed-off-by: Martin Robinson <martin@abandonedwig.info>

…`TransformStyle` more complete, a=testonly Automatic update from web-platform-tests layout: Make the implementation of used `TransformStyle` more complete Stylo was using a very incomplete method for calculating the used `TransformStyle` for boxes, which didn't incorporate all of the grouping properties from the specification. This change moves the functionality into Servo (as cannot properly compute this value without `FragmentFlags`) and makes it more complete. We still do not process the value of `contain`, `mask-iamge`, and `mask-boarder-source` as we do not support those values yet. Incidentally, this also fixes a panic that we were causing in WebRender, probably by going down a path that Gecko does not exercise. Stylo PR: servo/stylo#388 Signed-off-by: Martin Robinson <martin@abandonedwig.info> -- wpt-commits: 3b5dbefa6117860e83e16416778955a035962e05 wpt-pr: 60593

Fixes a compile warning from servo#388. Signed-off-by: Oriol Brufau <obrufau@igalia.com>

…#388) It's not possible to properly calculate these only looking at style, because the results depends on the used `overflow` value. Servo PR: servo/servo#45629 Signed-off-by: Martin Robinson <martin@abandonedwig.info>

Fixes a compile warning from #388. Signed-off-by: Oriol Brufau <obrufau@igalia.com>

…sform_style()`. r=firefox-style-system-reviewers,emilio It's not possible to properly calculate these only looking at style, because the results depends on the used `overflow` value. Imports servo/stylo#388 Imports servo/stylo#398 Differential Revision: https://phabricator.services.mozilla.com/D310917

…sform_style()`. r=firefox-style-system-reviewers,emilio It's not possible to properly calculate these only looking at style, because the results depends on the used `overflow` value. Imports servo#388 Imports servo#398 Differential Revision: https://phabricator.services.mozilla.com/D310917

mrobinson mentioned this pull request Jun 12, 2026

layout: Make the implementation of used TransformStyle more complete servo/servo#45629

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Loirooriol reviewed Jun 12, 2026

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servo-wpt-sync mentioned this pull request Jun 12, 2026

layout: Make the implementation of used TransformStyle more complete web-platform-tests/wpt#60593

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mrobinson force-pushed the complete-overrides_transform_style branch from 88ea543 to 033af4f Compare June 13, 2026 06:04

mrobinson changed the title ~~Make the implementation of overrides_transform_style() more complete~~ Remove overrides_transform_style() and get_used_transform_style() Jun 13, 2026

Remove overrides_transform_style() and get_used_transform_style()

33eb615

It's not possible to properly calculate these only looking at style, because the results depends on the used `overflow` value. Signed-off-by: Martin Robinson <martin@abandonedwig.info>

mrobinson force-pushed the complete-overrides_transform_style branch from 033af4f to 33eb615 Compare June 14, 2026 18:26

Loirooriol approved these changes Jun 16, 2026

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mrobinson added this pull request to the merge queue Jun 16, 2026

Merged via the queue into servo:main with commit 85b34b0 Jun 16, 2026
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mrobinson deleted the complete-overrides_transform_style branch June 16, 2026 11:40

Loirooriol mentioned this pull request Jun 18, 2026

Remove unused import: crate::computed_values #398

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mu-mostafa98 pushed a commit to mu-mostafa98/stylo that referenced this pull request Jun 22, 2026

Remove unused import: crate::computed_values (servo#398)

f59f742

Fixes a compile warning from servo#388. Signed-off-by: Oriol Brufau <obrufau@igalia.com>

Loirooriol added a commit that referenced this pull request Jul 1, 2026

Remove unused import: crate::computed_values (#398)

13e5568

Fixes a compile warning from #388. Signed-off-by: Oriol Brufau <obrufau@igalia.com>

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Remove `overrides_transform_style()` and `get_used_transform_style()` - #388

Remove `overrides_transform_style()` and `get_used_transform_style()`#388
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		!matches!(self.get_box().clone_overflow_x(), Overflow::Visible \| Overflow::Clip) \|\|
		!matches!(self.get_box().clone_overflow_y(), Overflow::Visible \| Overflow::Clip) \|\|

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