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LibWeb: Don't relayout when visibility changes between visible/hidden

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Layout will be identical for both of those values, so only a repaint is
necessary. If it changes to/from "collapse" however, we do need to
relayout. This means we can't simply use the "affects-layout" mechanism.
We have to write a little bit of custom code.

This makes Google Groups (and surely many other sites) significantly
more responsive by avoiding large amounts of layout work.
This commit is contained in:
Andreas Kling 2023-05-07 20:58:03 +02:00
parent 53d47c6614
commit f37f081f15
1 changed files with 10 additions and 1 deletions
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11
Userland/Libraries/LibWeb/DOM/Element.cpp
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@ -415,8 +415,17 @@ static RequiredInvalidation compute_required_invalidation(CSS::StyleProperties c
return RequiredInvalidation::Relayout;
if (*old_value == *new_value)
continue;
if (CSS::property_affects_layout(property_id))
// OPTIMIZATION: Special handling for CSS `visibility`:
if (property_id == CSS::PropertyID::Visibility) {
// We don't need to relayout if the visibility changes from visible to hidden or vice versa. Only collapse requires relayout.
if ((old_value->to_identifier() == CSS::ValueID::Collapse) != (new_value->to_identifier() == CSS::ValueID::Collapse))
return RequiredInvalidation::Relayout;
// Of course, we still have to repaint on any visibility change.
requires_repaint = true;
} else if (CSS::property_affects_layout(property_id)) {
return RequiredInvalidation::Relayout;
}
if (CSS::property_affects_stacking_context(property_id))
requires_stacking_context_tree_rebuild = true;
requires_repaint = true;