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layout2020: Don't create stacking contexts for empty fragments and boxes.

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This commit is contained in:
Josh Matthews 2020-06-02 16:59:43 -04:00
parent 08427ccee5
commit 56ff8f41e0
1 changed files with 21 additions and 0 deletions
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21
components/layout_2020/display_list/stacking_context.rs
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@ -448,6 +448,14 @@ impl Fragment {
return;
}
// If this fragment has a transform applied that makes it take up no spae
// then we don't need to create any stacking contexts for it.
let has_non_invertible_transform =
fragment.has_non_invertible_transform(&containing_block_info.rect.to_untyped());
if has_non_invertible_transform {
return;
}
fragment.build_stacking_context_tree(
fragment_ref,
builder,
@ -778,6 +786,15 @@ impl BoxFragment {
})
}
/// Returns true if the given style contains a transform that is not invertible.
fn has_non_invertible_transform(&self, containing_block: &Rect<Length>) -> bool {
let list = &self.style.get_box().transform;
match list.to_transform_3d_matrix(Some(containing_block)) {
Ok(t) => !t.0.is_invertible(),
Err(_) => false,
}
}
/// Returns the 4D matrix representing this fragment's transform.
pub fn calculate_transform_matrix(
&self,
@ -786,6 +803,10 @@ impl BoxFragment {
let list = &self.style.get_box().transform;
let transform =
LayoutTransform::from_untyped(&list.to_transform_3d_matrix(Some(&border_rect)).ok()?.0);
// 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.
assert_ne!(transform.m11, 0.);
assert_ne!(transform.m22, 0.);
let transform_origin = &self.style.get_box().transform_origin;
let transform_origin_x = transform_origin