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LibWeb: Implement hit testing a bit closer to spec

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We now perform hit testing in reverse paint order as described in CSS2's
section about the z-index property.
This commit is contained in:
Andreas Kling 2022-03-04 15:02:16 +01:00
parent 0401d7da36
commit 15ed0ebdc6
4 changed files with 74 additions and 26 deletions
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86
Userland/Libraries/LibWeb/Painting/StackingContext.cpp
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@ -148,27 +148,81 @@ void StackingContext::paint(PaintContext& context)
HitTestResult StackingContext::hit_test(const Gfx::IntPoint& position, HitTestType type) const
{
// NOTE: Hit testing basically happens in reverse painting order.
// https://www.w3.org/TR/CSS22/visuren.html#z-index
// 7. the child stacking contexts with positive stack levels (least positive first).
for (ssize_t i = m_children.size() - 1; i >= 0; --i) {
auto const& child = *m_children[i];
if (child.m_box.computed_values().z_index().value_or(0) < 0)
break;
auto result = child.hit_test(position, type);
if (result.layout_node)
return result;
}
HitTestResult result;
if (!is<InitialContainingBlock>(m_box)) {
result = m_box.hit_test(position, type);
} else {
// NOTE: InitialContainingBlock::hit_test() merely calls StackingContext::hit_test()
// so we call its base class instead.
result = verify_cast<InitialContainingBlock>(m_box).BlockContainer::hit_test(position, type);
// 6. the child stacking contexts with stack level 0 and the positioned descendants with stack level 0.
m_box.for_each_in_subtree_of_type<Layout::Box>([&](Layout::Box const& box) {
if (box.is_positioned() && !box.stacking_context()) {
result = box.hit_test(position, type);
if (result.layout_node)
return IterationDecision::Break;
}
return IterationDecision::Continue;
});
if (result.layout_node)
return result;
// 5. the in-flow, inline-level, non-positioned descendants, including inline tables and inline blocks.
if (m_box.children_are_inline() && is<BlockContainer>(m_box)) {
auto result = m_box.hit_test(position, type);
if (result.layout_node)
return result;
}
int z_index = m_box.computed_values().z_index().value_or(0);
// 4. the non-positioned floats.
m_box.for_each_in_subtree_of_type<Layout::Box>([&](Layout::Box const& box) {
if (box.is_floating()) {
result = box.hit_test(position, type);
if (result.layout_node)
return IterationDecision::Break;
}
return IterationDecision::Continue;
});
for (auto* child : m_children) {
int child_z_index = child->m_box.computed_values().z_index().value_or(0);
if (result.layout_node && (child_z_index < z_index))
continue;
auto result_here = child->hit_test(position, type);
if (result_here.layout_node)
result = result_here;
// 3. the in-flow, non-inline-level, non-positioned descendants.
if (!m_box.children_are_inline()) {
m_box.for_each_in_subtree_of_type<Layout::Box>([&](Layout::Box const& box) {
if (!box.is_absolutely_positioned() && !box.is_floating()) {
result = box.hit_test(position, type);
if (result.layout_node)
return IterationDecision::Break;
}
return IterationDecision::Continue;
});
if (result.layout_node)
return result;
}
return result;
// 2. the child stacking contexts with negative stack levels (most negative first).
for (ssize_t i = m_children.size() - 1; i >= 0; --i) {
auto const& child = *m_children[i];
if (child.m_box.computed_values().z_index().value_or(0) < 0)
break;
auto result = child.hit_test(position, type);
if (result.layout_node)
return result;
}
// 1. the background and borders of the element forming the stacking context.
if (m_box.absolute_border_box_rect().contains(position.to_type<float>())) {
return HitTestResult {
.layout_node = m_box,
};
}
return {};
}
void StackingContext::dump(int indent) const