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LibWeb: Factor out compute_y_position

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Factor out the code that computes the vertical position of a Box with
respect to its siblings so that it can be used when computing the
absolutely positioned divs as well.
This commit is contained in:
martinfalisse 2022-08-10 19:19:44 +02:00 committed by Andreas Kling
parent 99ae4fa161
commit 65e7126c48
Notes: sideshowbarker 2024-07-17 08:18:18 +09:00 
Author: https://github.com/martinfalisse
Commit: https://github.com/SerenityOS/serenity/commit/65e7126c48
Pull-request: https://github.com/SerenityOS/serenity/pull/14822
Reviewed-by: https://github.com/MacDue ✅
3 changed files with 58 additions and 51 deletions
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52
Userland/Libraries/LibWeb/Layout/BlockFormattingContext.cpp
View File

@ -505,57 +505,7 @@ void BlockFormattingContext::place_block_level_element_in_normal_flow_vertically
compute_vertical_box_model_metrics(child_box, containing_block);
float y = box_state.border_box_top();
Vector<float> collapsible_margins;
auto* relevant_sibling = child_box.previous_sibling_of_type<Layout::BlockContainer>();
while (relevant_sibling != nullptr) {
if (!relevant_sibling->is_absolutely_positioned() && !relevant_sibling->is_floating()) {
auto const& relevant_sibling_state = m_state.get(*relevant_sibling);
collapsible_margins.append(relevant_sibling_state.margin_bottom);
// NOTE: Empty (0-height) preceding siblings have their margins collapsed with *their* preceding sibling, etc.
if (relevant_sibling_state.border_box_height() > 0)
break;
collapsible_margins.append(relevant_sibling_state.margin_top);
}
relevant_sibling = relevant_sibling->previous_sibling_of_type<Layout::BlockContainer>();
}
if (relevant_sibling) {
// Collapse top margin with the collapsed margin(s) of preceding siblings.
collapsible_margins.append(box_state.margin_top);
float smallest_margin = 0;
float largest_margin = 0;
size_t negative_margin_count = 0;
for (auto margin : collapsible_margins) {
if (margin < 0)
++negative_margin_count;
largest_margin = max(largest_margin, margin);
smallest_margin = min(smallest_margin, margin);
}
float collapsed_margin = 0;
if (negative_margin_count == collapsible_margins.size()) {
// When all margins are negative, the size of the collapsed margin is the smallest (most negative) margin.
collapsed_margin = smallest_margin;
} else if (negative_margin_count > 0) {
// When negative margins are involved, the size of the collapsed margin is the sum of the largest positive margin and the smallest (most negative) negative margin.
collapsed_margin = largest_margin + smallest_margin;
} else {
// Otherwise, collapse all the adjacent margins by using only the largest one.
collapsed_margin = largest_margin;
}
auto const& relevant_sibling_state = m_state.get(*relevant_sibling);
y += relevant_sibling_state.offset.y()
+ relevant_sibling_state.content_height()
+ relevant_sibling_state.border_box_bottom()
+ collapsed_margin;
} else {
y += box_state.margin_top;
}
auto y = FormattingContext::compute_box_y_position_with_respect_to_siblings(child_box, box_state);
auto clear_floating_boxes = [&](FloatSideData& float_side) {
if (!float_side.current_boxes.is_empty()) {

55
Userland/Libraries/LibWeb/Layout/FormattingContext.cpp
View File

@ -1089,4 +1089,59 @@ float FormattingContext::containing_block_height_for(Box const& box, LayoutState
VERIFY_NOT_REACHED();
}
float FormattingContext::compute_box_y_position_with_respect_to_siblings(Box const& child_box, LayoutState::UsedValues const& box_state)
{
float y = box_state.border_box_top();
Vector<float> collapsible_margins;
auto* relevant_sibling = child_box.previous_sibling_of_type<Layout::BlockContainer>();
while (relevant_sibling != nullptr) {
if (!relevant_sibling->is_absolutely_positioned() && !relevant_sibling->is_floating()) {
auto const& relevant_sibling_state = m_state.get(*relevant_sibling);
collapsible_margins.append(relevant_sibling_state.margin_bottom);
// NOTE: Empty (0-height) preceding siblings have their margins collapsed with *their* preceding sibling, etc.
if (relevant_sibling_state.border_box_height() > 0)
break;
collapsible_margins.append(relevant_sibling_state.margin_top);
}
relevant_sibling = relevant_sibling->previous_sibling_of_type<Layout::BlockContainer>();
}
if (relevant_sibling) {
// Collapse top margin with the collapsed margin(s) of preceding siblings.
collapsible_margins.append(box_state.margin_top);
float smallest_margin = 0;
float largest_margin = 0;
size_t negative_margin_count = 0;
for (auto margin : collapsible_margins) {
if (margin < 0)
++negative_margin_count;
largest_margin = max(largest_margin, margin);
smallest_margin = min(smallest_margin, margin);
}
float collapsed_margin = 0;
if (negative_margin_count == collapsible_margins.size()) {
// When all margins are negative, the size of the collapsed margin is the smallest (most negative) margin.
collapsed_margin = smallest_margin;
} else if (negative_margin_count > 0) {
// When negative margins are involved, the size of the collapsed margin is the sum of the largest positive margin and the smallest (most negative) negative margin.
collapsed_margin = largest_margin + smallest_margin;
} else {
// Otherwise, collapse all the adjacent margins by using only the largest one.
collapsed_margin = largest_margin;
}
auto const& relevant_sibling_state = m_state.get(*relevant_sibling);
return y + relevant_sibling_state.offset.y()
+ relevant_sibling_state.content_height()
+ relevant_sibling_state.border_box_bottom()
+ collapsed_margin;
} else {
return y + box_state.margin_top;
}
}
}

2
Userland/Libraries/LibWeb/Layout/FormattingContext.h
View File

@ -63,6 +63,8 @@ public:
virtual void run_intrinsic_sizing(Box const&);
float compute_box_y_position_with_respect_to_siblings(Box const&, LayoutState::UsedValues const&);
protected:
FormattingContext(Type, LayoutState&, Box const&, FormattingContext* parent = nullptr);