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LibWeb: Margin bottom collapsing between parent and last child

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This commit is contained in:
Aliaksandr Kalenik 2022-12-28 21:42:46 +03:00 committed by Andreas Kling
parent 7088a87f49
commit 8259ff12bd
5 changed files with 105 additions and 65 deletions
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20
Base/res/html/misc/margin-collapse-4.html Normal file
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@ -0,0 +1,20 @@
<style>
#foo {
background-color: red;
width: 100px;
}
#bar {
background-color: green;
width: 50px;
height: 50px;
margin-top: -50px;
}
#baz {
background-color: blue;
width: 50px;
height: 50px;
margin-bottom: 100px;
}
</style>
<div id=foo><div id=baz></div></div>
<div id=bar></div>

89
Userland/Libraries/LibWeb/Layout/BlockFormattingContext.cpp
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@ -56,6 +56,16 @@ void BlockFormattingContext::run(Box const&, LayoutMode layout_mode, AvailableSp
layout_inline_children(root(), layout_mode, available_space);
else
layout_block_level_children(root(), layout_mode, available_space);
// Assign collapsed margin left after children layout of formatting context to the last child box
if (m_margin_state.current_collapsed_margin()) {
for (auto* child_box = root().last_child_of_type<Box>(); child_box; child_box = child_box->previous_sibling_of_type<Box>()) {
if (child_box->is_absolutely_positioned() || child_box->is_floating())
continue;
m_state.get_mutable(*child_box).margin_bottom = m_margin_state.current_collapsed_margin();
break;
}
}
}
void BlockFormattingContext::parent_context_did_dimension_child_root_box()
@ -358,6 +368,73 @@ static bool margins_collapse_through(Box const& box, LayoutState& state)
return state.get(box).border_box_height() == 0;
}
float BlockFormattingContext::compute_auto_height_for_block_level_element(Box const& box, AvailableSpace const& available_space)
{
if (creates_block_formatting_context(box)) {
return compute_auto_height_for_block_formatting_context_root(verify_cast<BlockContainer>(box));
}
auto const& box_state = m_state.get(box);
auto display = box.display();
if (display.is_flex_inside()) {
// https://drafts.csswg.org/css-flexbox-1/#algo-main-container
// NOTE: The automatic block size of a block-level flex container is its max-content size.
return calculate_max_content_height(box, available_space.width);
}
if (display.is_grid_inside()) {
// https://www.w3.org/TR/css-grid-2/#intrinsic-sizes
// In both inline and block formatting contexts, the grid container’s auto block size is its
// max-content size.
return calculate_max_content_height(box, available_space.width);
}
// https://www.w3.org/TR/CSS22/visudet.html#normal-block
// 10.6.3 Block-level non-replaced elements in normal flow when 'overflow' computes to 'visible'
// The element's height is the distance from its top content edge to the first applicable of the following:
// 1. the bottom edge of the last line box, if the box establishes a inline formatting context with one or more lines
if (box.children_are_inline() && !box_state.line_boxes.is_empty())
return box_state.line_boxes.last().bottom();
// 2. the bottom edge of the bottom (possibly collapsed) margin of its last in-flow child, if the child's bottom margin does not collapse with the element's bottom margin
// 3. the bottom border edge of the last in-flow child whose top margin doesn't collapse with the element's bottom margin
if (!box.children_are_inline()) {
for (auto* child_box = box.last_child_of_type<Box>(); child_box; child_box = child_box->previous_sibling_of_type<Box>()) {
if (child_box->is_absolutely_positioned() || child_box->is_floating())
continue;
// FIXME: This is hack. If the last child is a list-item marker box, we ignore it for purposes of height calculation.
// Perhaps markers should not be considered in-flow(?) Perhaps they should always be the first child of the list-item
// box instead of the last child.
if (child_box->is_list_item_marker_box())
continue;
auto const& child_box_state = m_state.get(*child_box);
// Ignore anonymous block containers with no lines. These don't count as in-flow block boxes.
if (child_box->is_anonymous() && child_box->is_block_container() && child_box_state.line_boxes.is_empty())
continue;
if (margins_collapse_through(*child_box, m_state)) {
continue;
}
float margin_bottom = m_margin_state.current_collapsed_margin();
if (box_state.padding_bottom == 0 && box_state.border_bottom == 0) {
m_margin_state.box_last_in_flow_child_margin_bottom_collapsed = true;
margin_bottom = 0;
}
return max(0.0f, child_box_state.offset.y() + child_box_state.content_height() + child_box_state.border_box_bottom() + margin_bottom);
}
}
// 4. zero, otherwise
return 0;
}
void BlockFormattingContext::layout_block_level_box(Box const& box, BlockContainer const& block_container, LayoutMode layout_mode, float& bottom_of_lowest_margin_box, AvailableSpace const& available_space, float& current_y)
{
auto& box_state = m_state.get_mutable(box);
@ -430,9 +507,12 @@ void BlockFormattingContext::layout_block_level_box(Box const& box, BlockContain
compute_height(box, available_space);
if (!margins_collapse_through(box, m_state)) {
m_margin_state.reset();
if (!m_margin_state.box_last_in_flow_child_margin_bottom_collapsed) {
m_margin_state.reset();
}
current_y = box_state.offset.y() + box_state.content_height() + box_state.border_box_bottom();
}
m_margin_state.box_last_in_flow_child_margin_bottom_collapsed = false;
m_margin_state.add_margin(box_state.margin_bottom);
m_margin_state.update_block_waiting_for_final_y_position();
@ -461,12 +541,7 @@ void BlockFormattingContext::layout_block_level_children(BlockContainer const& b
return IterationDecision::Continue;
});
// FIXME: The bottom margin of an in-flow block box with a 'height' of 'auto' collapses with its last in-flow block-level child's bottom margin, if:
// the box has no bottom padding, and
// the box has no bottom border, and
// the child's bottom margin neither collapses with a top margin that has clearance, nor (if the box's min-height is non-zero) with the box's top margin.
// https://www.w3.org/TR/CSS22/box.html#collapsing-margins
m_margin_state.reset();
m_margin_state.block_container_y_position_update_callback = {};
if (layout_mode == LayoutMode::IntrinsicSizing) {
auto& block_container_state = m_state.get_mutable(block_container);

3
Userland/Libraries/LibWeb/Layout/BlockFormattingContext.h
View file

@ -55,6 +55,8 @@ public:
private:
virtual bool is_block_formatting_context() const final { return true; }
float compute_auto_height_for_block_level_element(Box const&, AvailableSpace const&);
void compute_width_for_floating_box(Box const&, AvailableSpace const&);
void compute_width_for_block_level_replaced_element_in_normal_flow(ReplacedBox const&, AvailableSpace const&);
@ -114,6 +116,7 @@ private:
struct BlockMarginState {
Vector<float> current_collapsible_margins;
Function<void(float)> block_container_y_position_update_callback;
bool box_last_in_flow_child_margin_bottom_collapsed { false };
void add_margin(float margin)
{

57
Userland/Libraries/LibWeb/Layout/FormattingContext.cpp
View file

@ -274,63 +274,6 @@ static Gfx::FloatSize solve_replaced_size_constraint(LayoutState const& state, f
return { w, h };
}
float FormattingContext::compute_auto_height_for_block_level_element(Box const& box, AvailableSpace const& available_space) const
{
if (creates_block_formatting_context(box))
return compute_auto_height_for_block_formatting_context_root(verify_cast<BlockContainer>(box));
auto const& box_state = m_state.get(box);
auto display = box.display();
if (display.is_flex_inside()) {
// https://drafts.csswg.org/css-flexbox-1/#algo-main-container
// NOTE: The automatic block size of a block-level flex container is its max-content size.
return calculate_max_content_height(box, available_space.width);
}
if (display.is_grid_inside()) {
// https://www.w3.org/TR/css-grid-2/#intrinsic-sizes
// In both inline and block formatting contexts, the grid container’s auto block size is its
// max-content size.
return calculate_max_content_height(box, available_space.width);
}
// https://www.w3.org/TR/CSS22/visudet.html#normal-block
// 10.6.3 Block-level non-replaced elements in normal flow when 'overflow' computes to 'visible'
// The element's height is the distance from its top content edge to the first applicable of the following:
// 1. the bottom edge of the last line box, if the box establishes a inline formatting context with one or more lines
if (box.children_are_inline() && !box_state.line_boxes.is_empty())
return box_state.line_boxes.last().bottom();
// 2. the bottom edge of the bottom (possibly collapsed) margin of its last in-flow child, if the child's bottom margin does not collapse with the element's bottom margin
// FIXME: 3. the bottom border edge of the last in-flow child whose top margin doesn't collapse with the element's bottom margin
if (!box.children_are_inline()) {
for (auto* child_box = box.last_child_of_type<Box>(); child_box; child_box = child_box->previous_sibling_of_type<Box>()) {
if (child_box->is_absolutely_positioned() || child_box->is_floating())
continue;
// FIXME: This is hack. If the last child is a list-item marker box, we ignore it for purposes of height calculation.
// Perhaps markers should not be considered in-flow(?) Perhaps they should always be the first child of the list-item
// box instead of the last child.
if (child_box->is_list_item_marker_box())
continue;
auto const& child_box_state = m_state.get(*child_box);
// Ignore anonymous block containers with no lines. These don't count as in-flow block boxes.
if (child_box->is_anonymous() && child_box->is_block_container() && child_box_state.line_boxes.is_empty())
continue;
// FIXME: Handle margin collapsing.
return max(0.0f, child_box_state.offset.y() + child_box_state.content_height() + child_box_state.margin_box_bottom());
}
}
// 4. zero, otherwise
return 0;
}
// https://www.w3.org/TR/CSS22/visudet.html#root-height
float FormattingContext::compute_auto_height_for_block_formatting_context_root(BlockContainer const& root) const
{

1
Userland/Libraries/LibWeb/Layout/FormattingContext.h
View file

@ -105,7 +105,6 @@ protected:
static float tentative_width_for_replaced_element(LayoutState const&, ReplacedBox const&, CSS::Size const& computed_width, AvailableSpace const&);
static float tentative_height_for_replaced_element(LayoutState const&, ReplacedBox const&, CSS::Size const& computed_height, AvailableSpace const&);
float compute_auto_height_for_block_formatting_context_root(BlockContainer const&) const;
float compute_auto_height_for_block_level_element(Box const&, AvailableSpace const&) const;
ShrinkToFitResult calculate_shrink_to_fit_widths(Box const&);