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layout: Fix logic for transforms with non-invertible matrix (#37147)

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When the the current transformation matrix of a box isn't invertible,
the box and its content shouldn't be displayed.

However, the logic was broken:
- It was only checking the `transform` property, but not individual
transform properties like `scale`.
- It was treating matrices with m₁₁=0 or m₂₂=0 and non-invertible, even
when they can still be invertible and have a visible outcome.
- When m₁₁=0 or m₂₂=0 weren't caused by `transform`, it was replacing
the matrix with the identity.

Testing: Adding new WPT
Fixes: #37146

Signed-off-by: Oriol Brufau <obrufau@igalia.com>
This commit is contained in:
Oriol Brufau 2025-05-27 20:36:33 +02:00 • committed by GitHub
parent fef1dd9ea0
commit ac06b1cfcf
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4 changed files with 114 additions and 24 deletions
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31
components/layout/display_list/stacking_context.rs
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@ -834,16 +834,6 @@ impl Fragment {
_ => text_decorations,
};
// If this fragment has a transform applied that makes it take up no space
// then we don't need to create any stacking contexts for it.
let has_non_invertible_transform = fragment
.has_non_invertible_transform_or_zero_scale(
&containing_block.rect.to_untyped(),
);
if has_non_invertible_transform {
return;
}
fragment.build_stacking_context_tree(
fragment_clone,
stacking_context_tree,
@ -991,6 +981,13 @@ impl BoxFragment {
},
};
// <https://drafts.csswg.org/css-transforms/#transform-function-lists>
// > If a transform function causes the current transformation matrix of an object
// > to be non-invertible, the object and its content do not get displayed.
if !reference_frame_data.transform.is_invertible() {
return;
}
let new_spatial_id = stacking_context_tree.push_reference_frame(
reference_frame_data.origin.to_webrender(),
&containing_block.scroll_node_id,
@ -1622,15 +1619,6 @@ impl BoxFragment {
})
}
/// Returns true if the given style contains a transform that is not invertible.
fn has_non_invertible_transform_or_zero_scale(&self, containing_block: &Rect<Au>) -> bool {
let list = &self.style.get_box().transform;
match list.to_transform_3d_matrix(Some(&au_rect_to_length_rect(containing_block))) {
Ok(t) => !t.0.is_invertible() || t.0.m11 == 0. || t.0.m22 == 0.,
Err(_) => false,
}
}
/// Returns the 4D matrix representing this fragment's transform.
pub fn calculate_transform_matrix(&self, border_rect: &Rect<Au>) -> Option<LayoutTransform> {
let list = &self.style.get_box().transform;
@ -1660,11 +1648,6 @@ impl BoxFragment {
.then_rotate(rotate.0, rotate.1, rotate.2, angle)
.then_scale(scale.0, scale.1, scale.2)
.then(&translation);
// WebRender will end up dividing by the scale value of this transform, so we
// want to ensure we don't feed it a divisor of 0.
if transform.m11 == 0. || transform.m22 == 0. {
return Some(LayoutTransform::identity());
}
let transform_origin = &self.style.get_box().transform_origin;
let transform_origin_x = transform_origin