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LibWeb/Layout: Simplified margin collapsing

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Rather than accumulating margins into a vector, and then looping through
them when resolving the margin, it's much simpler to just update two
fields, and sum them when resolving.
This commit is contained in:
Jeremia Dominguez 2024-10-20 15:03:00 -05:00 • committed by Alexander Kalenik
commit eafa70331d
Notes: github-actions[bot] 2024-11-24 13:46:19 +00:00
2 changed files with 10 additions and 26 deletions
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24
Libraries/LibWeb/Layout/BlockFormattingContext.cpp
View file

@ -864,29 +864,7 @@ void BlockFormattingContext::resolve_vertical_box_model_metrics(Box const& box,
CSSPixels BlockFormattingContext::BlockMarginState::current_collapsed_margin() const CSSPixels BlockFormattingContext::BlockMarginState::current_collapsed_margin() const
{ {
CSSPixels smallest_margin = 0; return current_positive_collapsible_margin + current_negative_collapsible_margin;
CSSPixels largest_margin = 0;
size_t negative_margin_count = 0;
for (auto margin : current_collapsible_margins) {
if (margin < 0)
++negative_margin_count;
largest_margin = max(largest_margin, margin);
smallest_margin = min(smallest_margin, margin);
}
CSSPixels collapsed_margin = 0;
if (negative_margin_count == current_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;
}
return collapsed_margin;
} }
BlockFormattingContext::DidIntroduceClearance BlockFormattingContext::clear_floating_boxes(Node const& child_box, Optional<InlineFormattingContext&> inline_formatting_context) BlockFormattingContext::DidIntroduceClearance BlockFormattingContext::clear_floating_boxes(Node const& child_box, Optional<InlineFormattingContext&> inline_formatting_context)

12
Libraries/LibWeb/Layout/BlockFormattingContext.h
View file

@ -126,13 +126,18 @@ private:
}; };
struct BlockMarginState { struct BlockMarginState {
Vector<CSSPixels> current_collapsible_margins; CSSPixels current_positive_collapsible_margin;
CSSPixels current_negative_collapsible_margin;
Function<void(CSSPixels)> block_container_y_position_update_callback; Function<void(CSSPixels)> block_container_y_position_update_callback;
bool box_last_in_flow_child_margin_bottom_collapsed { false }; bool box_last_in_flow_child_margin_bottom_collapsed { false };
void add_margin(CSSPixels margin) void add_margin(CSSPixels margin)
{ {
current_collapsible_margins.append(margin); if (margin < 0) {
current_negative_collapsible_margin = min(margin, current_negative_collapsible_margin);
} else {
current_positive_collapsible_margin = max(margin, current_positive_collapsible_margin);
}
} }
void register_block_container_y_position_update_callback(ESCAPING Function<void(CSSPixels)> callback) void register_block_container_y_position_update_callback(ESCAPING Function<void(CSSPixels)> callback)
@ -158,7 +163,8 @@ private:
void reset() void reset()
{ {
block_container_y_position_update_callback = {}; block_container_y_position_update_callback = {};
current_collapsible_margins.clear(); current_negative_collapsible_margin = 0;
current_positive_collapsible_margin = 0;
} }
}; };