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ladybird/Userland/Libraries/LibWeb/Layout/FormattingContext.cpp

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/*
* Copyright (c) 2020-2022, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibWeb/Dump.h>
#include <LibWeb/Layout/BlockFormattingContext.h>
#include <LibWeb/Layout/Box.h>
#include <LibWeb/Layout/FlexFormattingContext.h>
#include <LibWeb/Layout/FormattingContext.h>
#include <LibWeb/Layout/GridFormattingContext.h>
#include <LibWeb/Layout/ReplacedBox.h>
#include <LibWeb/Layout/SVGFormattingContext.h>
#include <LibWeb/Layout/SVGSVGBox.h>
#include <LibWeb/Layout/TableFormattingContext.h>
#include <LibWeb/Layout/Viewport.h>
namespace Web::Layout {
FormattingContext::FormattingContext(Type type, LayoutState& state, Box const& context_box, FormattingContext* parent)
: m_type(type)
, m_parent(parent)
, m_context_box(context_box)
, m_state(state)
{
}
FormattingContext::~FormattingContext() = default;
// https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Block_formatting_context
bool FormattingContext::creates_block_formatting_context(Box const& box)
{
// NOTE: Replaced elements never create a BFC.
if (box.is_replaced_box())
return false;
// display: table
if (box.display().is_table_inside()) {
return false;
}
// display: flex
if (box.display().is_flex_inside()) {
return false;
}
// display: grid
if (box.display().is_grid_inside()) {
return false;
}
// NOTE: This function uses MDN as a reference, not because it's authoritative,
// but because they've gathered all the conditions in one convenient location.
// The root element of the document (<html>).
if (box.is_root_element())
return true;
// Floats (elements where float isn't none).
if (box.is_floating())
return true;
// Absolutely positioned elements (elements where position is absolute or fixed).
if (box.is_absolutely_positioned())
return true;
// Inline-blocks (elements with display: inline-block).
if (box.display().is_inline_block())
return true;
// Table cells (elements with display: table-cell, which is the default for HTML table cells).
if (box.display().is_table_cell())
return true;
// Table captions (elements with display: table-caption, which is the default for HTML table captions).
if (box.display().is_table_caption())
return true;
// FIXME: Anonymous table cells implicitly created by the elements with display: table, table-row, table-row-group, table-header-group, table-footer-group
// (which is the default for HTML tables, table rows, table bodies, table headers, and table footers, respectively), or inline-table.
// Block elements where overflow has a value other than visible and clip.
CSS::Overflow overflow_x = box.computed_values().overflow_x();
if ((overflow_x != CSS::Overflow::Visible) && (overflow_x != CSS::Overflow::Clip))
return true;
CSS::Overflow overflow_y = box.computed_values().overflow_y();
if ((overflow_y != CSS::Overflow::Visible) && (overflow_y != CSS::Overflow::Clip))
return true;
// display: flow-root.
if (box.display().is_flow_root_inside())
return true;
// FIXME: Elements with contain: layout, content, or paint.
if (box.parent()) {
auto parent_display = box.parent()->display();
// Flex items (direct children of the element with display: flex or inline-flex) if they are neither flex nor grid nor table containers themselves.
if (parent_display.is_flex_inside())
return true;
// Grid items (direct children of the element with display: grid or inline-grid) if they are neither flex nor grid nor table containers themselves.
if (parent_display.is_grid_inside())
return true;
}
// FIXME: Multicol containers (elements where column-count or column-width isn't auto, including elements with column-count: 1).
// FIXME: column-span: all should always create a new formatting context, even when the column-span: all element isn't contained by a multicol container (Spec change, Chrome bug).
return false;
}
Optional<FormattingContext::Type> FormattingContext::formatting_context_type_created_by_box(Box const& box)
{
if (box.is_replaced_box() && !box.can_have_children()) {
return Type::InternalReplaced;
}
if (!box.can_have_children())
return {};
if (is<SVGSVGBox>(box))
return Type::SVG;
auto display = box.display();
if (display.is_flex_inside())
return Type::Flex;
if (display.is_table_inside())
return Type::Table;
if (display.is_grid_inside())
return Type::Grid;
if (creates_block_formatting_context(box))
return Type::Block;
if (box.children_are_inline())
return {};
// The box is a block container that doesn't create its own BFC.
// It will be formatted by the containing BFC.
if (!display.is_flow_inside()) {
// HACK: Instead of crashing, create a dummy formatting context that does nothing.
// FIXME: Remove this once it's no longer needed. It currently swallows problem with standalone
// table-related boxes that don't get fixed up by CSS anonymous table box generation.
return Type::InternalDummy;
}
return {};
}
// FIXME: This is a hack. Get rid of it.
struct ReplacedFormattingContext : public FormattingContext {
ReplacedFormattingContext(LayoutState& state, Box const& box)
: FormattingContext(Type::Block, state, box)
{
}
virtual CSSPixels automatic_content_width() const override { return 0; }
virtual CSSPixels automatic_content_height() const override { return 0; }
virtual void run(Box const&, LayoutMode, AvailableSpace const&) override { }
};
// FIXME: This is a hack. Get rid of it.
struct DummyFormattingContext : public FormattingContext {
DummyFormattingContext(LayoutState& state, Box const& box)
: FormattingContext(Type::Block, state, box)
{
}
virtual CSSPixels automatic_content_width() const override { return 0; }
virtual CSSPixels automatic_content_height() const override { return 0; }
virtual void run(Box const&, LayoutMode, AvailableSpace const&) override { }
};
OwnPtr<FormattingContext> FormattingContext::create_independent_formatting_context_if_needed(LayoutState& state, Box const& child_box)
{
auto type = formatting_context_type_created_by_box(child_box);
if (!type.has_value())
return nullptr;
switch (type.value()) {
case Type::Block:
return make<BlockFormattingContext>(state, verify_cast<BlockContainer>(child_box), this);
case Type::SVG:
return make<SVGFormattingContext>(state, child_box, this);
case Type::Flex:
return make<FlexFormattingContext>(state, child_box, this);
case Type::Grid:
return make<GridFormattingContext>(state, child_box, this);
case Type::Table:
return make<TableFormattingContext>(state, child_box, this);
case Type::InternalReplaced:
return make<ReplacedFormattingContext>(state, child_box);
case Type::InternalDummy:
return make<DummyFormattingContext>(state, child_box);
case Type::Inline:
// IFC should always be created by a parent BFC directly.
VERIFY_NOT_REACHED();
break;
default:
VERIFY_NOT_REACHED();
}
}
OwnPtr<FormattingContext> FormattingContext::layout_inside(Box const& child_box, LayoutMode layout_mode, AvailableSpace const& available_space)
{
{
// OPTIMIZATION: If we're doing intrinsic sizing and `child_box` has definite size in both axes,
// we don't need to layout its insides. The size is resolvable without learning
// the metrics of whatever's inside the box.
auto const& used_values = m_state.get(child_box);
if (layout_mode == LayoutMode::IntrinsicSizing
&& used_values.width_constraint == SizeConstraint::None
&& used_values.height_constraint == SizeConstraint::None
&& used_values.has_definite_width()
&& used_values.has_definite_height()) {
return nullptr;
}
}
if (!child_box.can_have_children())
return {};
auto independent_formatting_context = create_independent_formatting_context_if_needed(m_state, child_box);
if (independent_formatting_context)
independent_formatting_context->run(child_box, layout_mode, available_space);
else
run(child_box, layout_mode, available_space);
return independent_formatting_context;
}
CSSPixels FormattingContext::greatest_child_width(Box const& box) const
{
CSSPixels max_width = 0;
if (box.children_are_inline()) {
for (auto& line_box : m_state.get(box).line_boxes) {
max_width = max(max_width, line_box.width());
}
} else {
box.for_each_child_of_type<Box>([&](Box const& child) {
if (!child.is_absolutely_positioned())
max_width = max(max_width, m_state.get(child).margin_box_width());
});
}
return max_width;
}
FormattingContext::ShrinkToFitResult FormattingContext::calculate_shrink_to_fit_widths(Box const& box)
{
return {
.preferred_width = calculate_max_content_width(box),
.preferred_minimum_width = calculate_min_content_width(box),
};
}
CSSPixelSize FormattingContext::solve_replaced_size_constraint(CSSPixels input_width, CSSPixels input_height, Box const& box, AvailableSpace const& available_space) const
{
// 10.4 Minimum and maximum widths: 'min-width' and 'max-width'
// https://www.w3.org/TR/CSS22/visudet.html#min-max-widths
auto const& containing_block = *box.non_anonymous_containing_block();
auto const& containing_block_state = m_state.get(containing_block);
auto width_of_containing_block = containing_block_state.content_width();
auto height_of_containing_block = containing_block_state.content_height();
auto min_width = box.computed_values().min_width().is_auto() ? 0 : box.computed_values().min_width().to_px(box, width_of_containing_block);
auto specified_max_width = should_treat_max_width_as_none(box, available_space.width) ? input_width : box.computed_values().max_width().to_px(box, width_of_containing_block);
auto max_width = max(min_width, specified_max_width);
auto min_height = box.computed_values().min_height().is_auto() ? 0 : box.computed_values().min_height().to_px(box, height_of_containing_block);
auto specified_max_height = should_treat_max_height_as_none(box, available_space.height) ? input_height : box.computed_values().max_height().to_px(box, height_of_containing_block);
auto max_height = max(min_height, specified_max_height);
CSSPixelFraction aspect_ratio = *box.preferred_aspect_ratio();
// These are from the "Constraint Violation" table in spec, but reordered so that each condition is
// interpreted as mutually exclusive to any other.
if (input_width < min_width && input_height > max_height)
return { min_width, max_height };
if (input_width > max_width && input_height < min_height)
return { max_width, min_height };
if (input_width > max_width && input_height > max_height && max_width / input_width <= max_height / input_height)
return { max_width, max(min_height, max_width / aspect_ratio) };
if (input_width > max_width && input_height > max_height && max_width / input_width > max_height / input_height)
return { max(min_width, max_height * aspect_ratio), max_height };
if (input_width < min_width && input_height < min_height && min_width / input_width <= min_height / input_height)
return { min(max_width, min_height * aspect_ratio), min_height };
if (input_width < min_width && input_height < min_height && min_width / input_width > min_height / input_height)
return { min_width, min(max_height, min_width / aspect_ratio) };
if (input_width > max_width)
return { max_width, max(max_width / aspect_ratio, min_height) };
if (input_width < min_width)
return { min_width, min(min_width / aspect_ratio, max_height) };
if (input_height > max_height)
return { max(max_height * aspect_ratio, min_width), max_height };
if (input_height < min_height)
return { min(min_height * aspect_ratio, max_width), min_height };
return { input_width, input_height };
}
Optional<CSSPixels> FormattingContext::compute_auto_height_for_absolutely_positioned_element(Box const& box, AvailableSpace const& available_space, BeforeOrAfterInsideLayout before_or_after_inside_layout) const
{
// NOTE: CSS 2.2 tells us to use the "auto height for block formatting context roots" here.
// That's fine as long as the box is a BFC root.
if (creates_block_formatting_context(box)) {
if (before_or_after_inside_layout == BeforeOrAfterInsideLayout::Before)
return {};
return compute_auto_height_for_block_formatting_context_root(box);
}
// NOTE: For anything else, we use the fit-content height.
// This should eventually be replaced by the new absolute positioning model:
// https://www.w3.org/TR/css-position-3/#abspos-layout
return calculate_fit_content_height(box, m_state.get(box).available_inner_space_or_constraints_from(available_space));
}
// https://www.w3.org/TR/CSS22/visudet.html#root-height
CSSPixels FormattingContext::compute_auto_height_for_block_formatting_context_root(Box const& root) const
{
// 10.6.7 'Auto' heights for block formatting context roots
Optional<CSSPixels> top;
Optional<CSSPixels> bottom;
if (root.children_are_inline()) {
// If it only has inline-level children, the height is the distance between
// the top content edge and the bottom of the bottommost line box.
auto const& line_boxes = m_state.get(root).line_boxes;
top = 0;
if (!line_boxes.is_empty())
bottom = line_boxes.last().bottom();
} else {
// If it has block-level children, the height is the distance between
// the top margin-edge of the topmost block-level child box
// and the bottom margin-edge of the bottommost block-level child box.
root.for_each_child_of_type<Box>([&](Layout::Box& child_box) {
// Absolutely positioned children are ignored,
// and relatively positioned boxes are considered without their offset.
// Note that the child box may be an anonymous block box.
if (child_box.is_absolutely_positioned())
return IterationDecision::Continue;
// FIXME: This doesn't look right.
if ((root.computed_values().overflow_y() == CSS::Overflow::Visible) && child_box.is_floating())
return IterationDecision::Continue;
auto const& child_box_state = m_state.get(child_box);
CSSPixels child_box_top = child_box_state.offset.y() - child_box_state.margin_box_top();
CSSPixels child_box_bottom = child_box_state.offset.y() + child_box_state.content_height() + child_box_state.margin_box_bottom();
if (!top.has_value() || child_box_top < top.value())
top = child_box_top;
if (!bottom.has_value() || child_box_bottom > bottom.value())
bottom = child_box_bottom;
return IterationDecision::Continue;
});
}
// In addition, if the element has any floating descendants
// whose bottom margin edge is below the element's bottom content edge,
// then the height is increased to include those edges.
for (auto floating_box : m_state.get(root).floating_descendants()) {
// NOTE: Floating box coordinates are relative to their own containing block,
// which may or may not be the BFC root.
auto margin_box = margin_box_rect_in_ancestor_coordinate_space(*floating_box, root);
CSSPixels floating_box_bottom_margin_edge = margin_box.bottom();
if (!bottom.has_value() || floating_box_bottom_margin_edge > bottom.value())
bottom = floating_box_bottom_margin_edge;
}
return max(CSSPixels(0.0f), bottom.value_or(0) - top.value_or(0));
}
// 10.3.2 Inline, replaced elements, https://www.w3.org/TR/CSS22/visudet.html#inline-replaced-width
CSSPixels FormattingContext::tentative_width_for_replaced_element(Box const& box, CSS::Size const& computed_width, AvailableSpace const& available_space) const
{
// Treat percentages of indefinite containing block widths as 0 (the initial width).
if (computed_width.is_percentage() && !m_state.get(*box.containing_block()).has_definite_width())
return 0;
auto computed_height = should_treat_height_as_auto(box, available_space) ? CSS::Size::make_auto() : box.computed_values().height();
CSSPixels used_width = 0;
if (computed_width.is_auto()) {
used_width = computed_width.to_px(box, available_space.width.to_px_or_zero());
} else {
used_width = calculate_inner_width(box, available_space.width, computed_width);
}
// If 'height' and 'width' both have computed values of 'auto' and the element also has an intrinsic width,
// then that intrinsic width is the used value of 'width'.
if (computed_height.is_auto() && computed_width.is_auto() && box.has_natural_width())
return box.natural_width().value();
// If 'height' and 'width' both have computed values of 'auto' and the element has no intrinsic width,
// but does have an intrinsic height and intrinsic ratio;
// or if 'width' has a computed value of 'auto',
// 'height' has some other computed value, and the element does have an intrinsic ratio; then the used value of 'width' is:
//
// (used height) * (intrinsic ratio)
if ((computed_height.is_auto() && computed_width.is_auto() && !box.has_natural_width() && box.has_natural_height() && box.has_preferred_aspect_ratio())
|| (computed_width.is_auto() && !computed_height.is_auto() && box.has_preferred_aspect_ratio())) {
return compute_height_for_replaced_element(box, available_space) * box.preferred_aspect_ratio().value();
}
// If 'height' and 'width' both have computed values of 'auto' and the element has an intrinsic ratio but no intrinsic height or width,
// then the used value of 'width' is undefined in CSS 2.2. However, it is suggested that, if the containing block's width does not itself
// depend on the replaced element's width, then the used value of 'width' is calculated from the constraint equation used for block-level,
// non-replaced elements in normal flow.
if (computed_height.is_auto() && computed_width.is_auto() && !box.has_natural_width() && !box.has_natural_height() && box.has_preferred_aspect_ratio()) {
return calculate_stretch_fit_width(box, available_space.width);
}
// Otherwise, if 'width' has a computed value of 'auto', and the element has an intrinsic width, then that intrinsic width is the used value of 'width'.
if (computed_width.is_auto() && box.has_natural_width())
return box.natural_width().value();
// Otherwise, if 'width' has a computed value of 'auto', but none of the conditions above are met, then the used value of 'width' becomes 300px.
// If 300px is too wide to fit the device, UAs should use the width of the largest rectangle that has a 2:1 ratio and fits the device instead.
if (computed_width.is_auto())
return 300;
return used_width;
}
void FormattingContext::compute_width_for_absolutely_positioned_element(Box const& box, AvailableSpace const& available_space)
{
if (box_is_sized_as_replaced_element(box))
compute_width_for_absolutely_positioned_replaced_element(box, available_space);
else
compute_width_for_absolutely_positioned_non_replaced_element(box, available_space);
}
void FormattingContext::compute_height_for_absolutely_positioned_element(Box const& box, AvailableSpace const& available_space, BeforeOrAfterInsideLayout before_or_after_inside_layout)
{
if (box_is_sized_as_replaced_element(box))
compute_height_for_absolutely_positioned_replaced_element(box, available_space, before_or_after_inside_layout);
else
compute_height_for_absolutely_positioned_non_replaced_element(box, available_space, before_or_after_inside_layout);
}
CSSPixels FormattingContext::compute_width_for_replaced_element(Box const& box, AvailableSpace const& available_space) const
{
// 10.3.4 Block-level, replaced elements in normal flow...
// 10.3.2 Inline, replaced elements
auto zero_value = CSS::Length::make_px(0);
auto width_of_containing_block = available_space.width.to_px_or_zero();
auto computed_width = should_treat_width_as_auto(box, available_space) ? CSS::Size::make_auto() : box.computed_values().width();
auto computed_height = should_treat_height_as_auto(box, available_space) ? CSS::Size::make_auto() : box.computed_values().height();
// 1. The tentative used width is calculated (without 'min-width' and 'max-width')
auto used_width = tentative_width_for_replaced_element(box, computed_width, available_space);
if (computed_width.is_auto() && computed_height.is_auto() && box.has_preferred_aspect_ratio()) {
CSSPixels w = used_width;
CSSPixels h = tentative_height_for_replaced_element(box, computed_height, available_space);
used_width = solve_replaced_size_constraint(w, h, box, available_space).width();
return used_width;
}
// 2. The tentative used width is greater than 'max-width', the rules above are applied again,
// but this time using the computed value of 'max-width' as the computed value for 'width'.
if (!should_treat_max_width_as_none(box, available_space.width)) {
auto const& computed_max_width = box.computed_values().max_width();
if (used_width > computed_max_width.to_px(box, width_of_containing_block)) {
used_width = tentative_width_for_replaced_element(box, computed_max_width, available_space);
}
}
// 3. If the resulting width is smaller than 'min-width', the rules above are applied again,
// but this time using the value of 'min-width' as the computed value for 'width'.
auto computed_min_width = box.computed_values().min_width();
if (!computed_min_width.is_auto()) {
if (used_width < computed_min_width.to_px(box, width_of_containing_block)) {
used_width = tentative_width_for_replaced_element(box, computed_min_width, available_space);
}
}
return used_width;
}
// 10.6.2 Inline replaced elements, block-level replaced elements in normal flow, 'inline-block' replaced elements in normal flow and floating replaced elements
// https://www.w3.org/TR/CSS22/visudet.html#inline-replaced-height
CSSPixels FormattingContext::tentative_height_for_replaced_element(Box const& box, CSS::Size const& computed_height, AvailableSpace const& available_space) const
{
// If 'height' and 'width' both have computed values of 'auto' and the element also has
// an intrinsic height, then that intrinsic height is the used value of 'height'.
if (should_treat_width_as_auto(box, available_space) && should_treat_height_as_auto(box, available_space) && box.has_natural_height())
return box.natural_height().value();
// Otherwise, if 'height' has a computed value of 'auto', and the element has an intrinsic ratio then the used value of 'height' is:
//
// (used width) / (intrinsic ratio)
if (computed_height.is_auto() && box.has_preferred_aspect_ratio())
return m_state.get(box).content_width() / box.preferred_aspect_ratio().value();
// Otherwise, if 'height' has a computed value of 'auto', and the element has an intrinsic height, then that intrinsic height is the used value of 'height'.
if (computed_height.is_auto() && box.has_natural_height())
return box.natural_height().value();
// Otherwise, if 'height' has a computed value of 'auto', but none of the conditions above are met,
// then the used value of 'height' must be set to the height of the largest rectangle that has a 2:1 ratio, has a height not greater than 150px,
// and has a width not greater than the device width.
if (computed_height.is_auto())
return 150;
// FIXME: Handle cases when available_space is not definite.
return calculate_inner_height(box, available_space.height, computed_height);
}
CSSPixels FormattingContext::compute_height_for_replaced_element(Box const& box, AvailableSpace const& available_space) const
{
// 10.6.2 Inline replaced elements
// 10.6.4 Block-level replaced elements in normal flow
// 10.6.6 Floating replaced elements
// 10.6.10 'inline-block' replaced elements in normal flow
auto height_of_containing_block = m_state.get(*box.non_anonymous_containing_block()).content_height();
auto computed_width = should_treat_width_as_auto(box, available_space) ? CSS::Size::make_auto() : box.computed_values().width();
auto computed_height = should_treat_height_as_auto(box, available_space) ? CSS::Size::make_auto() : box.computed_values().height();
// 1. The tentative used height is calculated (without 'min-height' and 'max-height')
CSSPixels used_height = tentative_height_for_replaced_element(box, computed_height, available_space);
// However, for replaced elements with both 'width' and 'height' computed as 'auto',
// use the algorithm under 'Minimum and maximum widths'
// https://www.w3.org/TR/CSS22/visudet.html#min-max-widths
// to find the used width and height.
if (computed_width.is_auto() && computed_height.is_auto() && box.has_preferred_aspect_ratio()) {
CSSPixels w = tentative_width_for_replaced_element(box, computed_width, available_space);
CSSPixels h = used_height;
used_height = solve_replaced_size_constraint(w, h, box, available_space).height();
return used_height;
}
// 2. If this tentative height is greater than 'max-height', the rules above are applied again,
// but this time using the value of 'max-height' as the computed value for 'height'.
if (!should_treat_max_height_as_none(box, available_space.height)) {
auto const& computed_max_height = box.computed_values().max_height();
if (used_height > computed_max_height.to_px(box, height_of_containing_block)) {
used_height = tentative_height_for_replaced_element(box, computed_max_height, available_space);
}
}
// 3. If the resulting height is smaller than 'min-height', the rules above are applied again,
// but this time using the value of 'min-height' as the computed value for 'height'.
auto computed_min_height = box.computed_values().min_height();
if (!computed_min_height.is_auto()) {
if (used_height < computed_min_height.to_px(box, height_of_containing_block)) {
used_height = tentative_height_for_replaced_element(box, computed_min_height, available_space);
}
}
return used_height;
}
void FormattingContext::compute_width_for_absolutely_positioned_non_replaced_element(Box const& box, AvailableSpace const& available_space)
{
auto width_of_containing_block = available_space.width.to_px_or_zero();
auto& computed_values = box.computed_values();
auto zero_value = CSS::Length::make_px(0);
auto margin_left = CSS::Length::make_auto();
auto margin_right = CSS::Length::make_auto();
auto const border_left = computed_values.border_left().width;
auto const border_right = computed_values.border_right().width;
auto const padding_left = computed_values.padding().left().to_px(box, width_of_containing_block);
auto const padding_right = computed_values.padding().right().to_px(box, width_of_containing_block);
auto computed_left = computed_values.inset().left();
auto computed_right = computed_values.inset().right();
auto left = computed_values.inset().left().to_px(box, width_of_containing_block);
auto right = computed_values.inset().right().to_px(box, width_of_containing_block);
auto try_compute_width = [&](CSS::Length const& a_width) {
margin_left = computed_values.margin().left().resolved(box, width_of_containing_block);
margin_right = computed_values.margin().right().resolved(box, width_of_containing_block);
auto width = a_width;
auto solve_for_left = [&] {
return width_of_containing_block - margin_left.to_px(box) - border_left - padding_left - width.to_px(box) - padding_right - border_right - margin_right.to_px(box) - right;
};
auto solve_for_width = [&] {
return CSS::Length::make_px(max(CSSPixels(0), width_of_containing_block - left - margin_left.to_px(box) - border_left - padding_left - padding_right - border_right - margin_right.to_px(box) - right));
};
auto solve_for_right = [&] {
return width_of_containing_block - left - margin_left.to_px(box) - border_left - padding_left - width.to_px(box) - padding_right - border_right - margin_right.to_px(box);
};
// If all three of 'left', 'width', and 'right' are 'auto':
if (computed_left.is_auto() && width.is_auto() && computed_right.is_auto()) {
// First set any 'auto' values for 'margin-left' and 'margin-right' to 0.
if (margin_left.is_auto())
margin_left = CSS::Length::make_px(0);
if (margin_right.is_auto())
margin_right = CSS::Length::make_px(0);
// Then, if the 'direction' property of the element establishing the static-position containing block
// is 'ltr' set 'left' to the static position and apply rule number three below;
// otherwise, set 'right' to the static position and apply rule number one below.
// FIXME: This is very hackish.
auto static_position = calculate_static_position(box);
left = static_position.x();
goto Rule3;
}
// If none of the three is auto:
if (!computed_left.is_auto() && !width.is_auto() && !computed_right.is_auto()) {
// If both margin-left and margin-right are auto,
// solve the equation under the extra constraint that the two margins get equal values
// FIXME: unless this would make them negative, in which case when direction of the containing block is ltr (rtl), set margin-left (margin-right) to 0 and solve for margin-right (margin-left).
auto size_available_for_margins = width_of_containing_block - border_left - padding_left - width.to_px(box) - padding_right - border_right - right;
if (margin_left.is_auto() && margin_right.is_auto()) {
margin_left = CSS::Length::make_px(size_available_for_margins / 2);
margin_right = CSS::Length::make_px(size_available_for_margins / 2);
return width;
}
// If one of margin-left or margin-right is auto, solve the equation for that value.
if (margin_left.is_auto()) {
margin_left = CSS::Length::make_px(size_available_for_margins);
return width;
}
if (margin_right.is_auto()) {
margin_right = CSS::Length::make_px(size_available_for_margins);
return width;
}
// If the values are over-constrained, ignore the value for left
// (in case the direction property of the containing block is rtl)
// or right (in case direction is ltr) and solve for that value.
// NOTE: At this point we *are* over-constrained since none of margin-left, left, width, right, or margin-right are auto.
// FIXME: Check direction.
right = solve_for_right();
return width;
}
if (margin_left.is_auto())
margin_left = CSS::Length::make_px(0);
if (margin_right.is_auto())
margin_right = CSS::Length::make_px(0);
// 1. 'left' and 'width' are 'auto' and 'right' is not 'auto',
// then the width is shrink-to-fit. Then solve for 'left'
if (computed_left.is_auto() && width.is_auto() && !computed_right.is_auto()) {
auto result = calculate_shrink_to_fit_widths(box);
auto available_width = solve_for_width();
width = CSS::Length::make_px(min(max(result.preferred_minimum_width, available_width.to_px(box)), result.preferred_width));
left = solve_for_left();
}
// 2. 'left' and 'right' are 'auto' and 'width' is not 'auto',
// then if the 'direction' property of the element establishing
// the static-position containing block is 'ltr' set 'left'
// to the static position, otherwise set 'right' to the static position.
// Then solve for 'left' (if 'direction is 'rtl') or 'right' (if 'direction' is 'ltr').
else if (computed_left.is_auto() && computed_right.is_auto() && !width.is_auto()) {
// FIXME: Check direction
auto static_position = calculate_static_position(box);
left = static_position.x();
right = solve_for_right();
}
// 3. 'width' and 'right' are 'auto' and 'left' is not 'auto',
// then the width is shrink-to-fit. Then solve for 'right'
else if (width.is_auto() && computed_right.is_auto() && !computed_left.is_auto()) {
Rule3:
auto result = calculate_shrink_to_fit_widths(box);
auto available_width = solve_for_width();
width = CSS::Length::make_px(min(max(result.preferred_minimum_width, available_width.to_px(box)), result.preferred_width));
right = solve_for_right();
}
// 4. 'left' is 'auto', 'width' and 'right' are not 'auto', then solve for 'left'
else if (computed_left.is_auto() && !width.is_auto() && !computed_right.is_auto()) {
left = solve_for_left();
}
// 5. 'width' is 'auto', 'left' and 'right' are not 'auto', then solve for 'width'
else if (width.is_auto() && !computed_left.is_auto() && !computed_right.is_auto()) {
width = solve_for_width();
}
// 6. 'right' is 'auto', 'left' and 'width' are not 'auto', then solve for 'right'
else if (computed_right.is_auto() && !computed_left.is_auto() && !width.is_auto()) {
right = solve_for_right();
}
return width;
};
// 1. The tentative used width is calculated (without 'min-width' and 'max-width')
auto used_width = try_compute_width([&] {
if (computed_values.width().is_auto())
return CSS::Length::make_auto();
return CSS::Length::make_px(calculate_inner_width(box, available_space.width, computed_values.width()));
}());
// 2. The tentative used width is greater than 'max-width', the rules above are applied again,
// but this time using the computed value of 'max-width' as the computed value for 'width'.
if (!should_treat_max_width_as_none(box, available_space.width)) {
auto max_width = calculate_inner_width(box, available_space.width, computed_values.max_width());
if (used_width.to_px(box) > max_width) {
used_width = try_compute_width(CSS::Length::make_px(max_width));
}
}
// 3. If the resulting width is smaller than 'min-width', the rules above are applied again,
// but this time using the value of 'min-width' as the computed value for 'width'.
if (!computed_values.min_width().is_auto()) {
auto min_width = calculate_inner_width(box, available_space.width, computed_values.min_width());
if (used_width.to_px(box) < min_width) {
used_width = try_compute_width(CSS::Length::make_px(min_width));
}
}
auto& box_state = m_state.get_mutable(box);
box_state.set_content_width(used_width.to_px(box));
box_state.inset_left = left;
box_state.inset_right = right;
box_state.margin_left = margin_left.to_px(box);
box_state.margin_right = margin_right.to_px(box);
box_state.padding_left = padding_left;
box_state.padding_right = padding_right;
}
void FormattingContext::compute_width_for_absolutely_positioned_replaced_element(Box const& box, AvailableSpace const& available_space)
{
// 10.3.8 Absolutely positioned, replaced elements
// In this case, section 10.3.7 applies up through and including the constraint equation,
// but the rest of section 10.3.7 is replaced by the following rules:
// 1. The used value of 'width' is determined as for inline replaced elements.
if (is<ReplacedBox>(box)) {
// FIXME: This const_cast is gross.
static_cast<ReplacedBox&>(const_cast<Box&>(box)).prepare_for_replaced_layout();
}
auto width = compute_width_for_replaced_element(box, available_space);
auto width_of_containing_block = available_space.width.to_px_or_zero();
auto available = width_of_containing_block - width;
auto const& computed_values = box.computed_values();
auto left = computed_values.inset().left();
auto margin_left = computed_values.margin().left();
auto right = computed_values.inset().right();
auto margin_right = computed_values.margin().right();
auto static_position = calculate_static_position(box);
auto to_px = [&](const CSS::LengthPercentage& l) {
return l.to_px(box, width_of_containing_block);
};
// If 'margin-left' or 'margin-right' is specified as 'auto' its used value is determined by the rules below.
// 2. If both 'left' and 'right' have the value 'auto', then if the 'direction' property of the
// element establishing the static-position containing block is 'ltr', set 'left' to the static
// position; else if 'direction' is 'rtl', set 'right' to the static position.
if (left.is_auto() && right.is_auto()) {
left = CSS::Length::make_px(static_position.x());
}
// 3. If 'left' or 'right' are 'auto', replace any 'auto' on 'margin-left' or 'margin-right' with '0'.
if (left.is_auto() || right.is_auto()) {
if (margin_left.is_auto())
margin_left = CSS::Length::make_px(0);
if (margin_right.is_auto())
margin_right = CSS::Length::make_px(0);
}
// 4. If at this point both 'margin-left' and 'margin-right' are still 'auto', solve the equation
// under the extra constraint that the two margins must get equal values, unless this would make
// them negative, in which case when the direction of the containing block is 'ltr' ('rtl'),
// set 'margin-left' ('margin-right') to zero and solve for 'margin-right' ('margin-left').
if (margin_left.is_auto() && margin_right.is_auto()) {
auto remainder = available - to_px(left) - to_px(right);
if (remainder < 0) {
margin_left = CSS::Length::make_px(0);
margin_right = CSS::Length::make_px(0);
} else {
margin_left = CSS::Length::make_px(remainder / 2);
margin_right = CSS::Length::make_px(remainder / 2);
}
}
// 5. If at this point there is an 'auto' left, solve the equation for that value.
if (left.is_auto()) {
left = CSS::Length::make_px(available - to_px(right) - to_px(margin_left) - to_px(margin_right));
} else if (right.is_auto()) {
right = CSS::Length::make_px(available - to_px(left) - to_px(margin_left) - to_px(margin_right));
} else if (margin_left.is_auto()) {
margin_left = CSS::Length::make_px(available - to_px(left) - to_px(right) - to_px(margin_right));
} else if (margin_right.is_auto()) {
margin_right = CSS::Length::make_px(available - to_px(left) - to_px(margin_left) - to_px(right));
}
// 6. If at this point the values are over-constrained, ignore the value for either 'left'
// (in case the 'direction' property of the containing block is 'rtl') or 'right'
// (in case 'direction' is 'ltr') and solve for that value.
if (0 != available - to_px(left) - to_px(right) - to_px(margin_left) - to_px(margin_right)) {
right = CSS::Length::make_px(available - to_px(left) - to_px(margin_left) - to_px(margin_right));
}
auto& box_state = m_state.get_mutable(box);
box_state.inset_left = to_px(left);
box_state.inset_right = to_px(right);
box_state.margin_left = to_px(margin_left);
box_state.margin_right = to_px(margin_right);
box_state.set_content_width(width);
}
// https://drafts.csswg.org/css-position-3/#abs-non-replaced-height
void FormattingContext::compute_height_for_absolutely_positioned_non_replaced_element(Box const& box, AvailableSpace const& available_space, BeforeOrAfterInsideLayout before_or_after_inside_layout)
{
// 5.3. The Height Of Absolutely Positioned, Non-Replaced Elements
// For absolutely positioned elements, the used values of the vertical dimensions must satisfy this constraint:
// top + margin-top + border-top-width + padding-top + height + padding-bottom + border-bottom-width + margin-bottom + bottom = height of containing block
// NOTE: This function is called twice: both before and after inside layout.
// In the before pass, if it turns out we need the automatic height of the box, we abort these steps.
// This allows the box to retain an indefinite height from the perspective of inside layout.
auto apply_min_max_height_constraints = [this, &box, &available_space](CSSPixels unconstrained_height) -> CSSPixels {
auto const& computed_min_height = box.computed_values().min_height();
auto const& computed_max_height = box.computed_values().max_height();
auto constrained_height = unconstrained_height;
if (!computed_max_height.is_none()) {
auto inner_max_height = calculate_inner_height(box, available_space.height, computed_max_height);
constrained_height = min(constrained_height, inner_max_height);
}
if (!computed_min_height.is_auto()) {
auto inner_min_height = calculate_inner_height(box, available_space.height, computed_min_height);
constrained_height = max(constrained_height, inner_min_height);
}
return constrained_height;
};
auto margin_top = box.computed_values().margin().top();
auto margin_bottom = box.computed_values().margin().bottom();
auto top = box.computed_values().inset().top();
auto bottom = box.computed_values().inset().bottom();
auto height = box.computed_values().height();
auto width_of_containing_block = containing_block_width_for(box);
auto height_of_containing_block = available_space.height.to_px_or_zero();
enum class ClampToZero {
No,
Yes,
};
auto solve_for = [&](CSS::Length length, ClampToZero clamp_to_zero = ClampToZero::No) {
auto unclamped_value = height_of_containing_block
- top.to_px(box, height_of_containing_block)
- margin_top.to_px(box, width_of_containing_block)
- box.computed_values().border_top().width
- box.computed_values().padding().top().to_px(box, width_of_containing_block)
- height.to_px(box, height_of_containing_block)
- box.computed_values().padding().bottom().to_px(box, width_of_containing_block)
- box.computed_values().border_bottom().width
- margin_bottom.to_px(box, width_of_containing_block)
- bottom.to_px(box, height_of_containing_block)
+ length.to_px(box);
if (clamp_to_zero == ClampToZero::Yes)
return CSS::Length::make_px(max(CSSPixels(0), unclamped_value));
return CSS::Length::make_px(unclamped_value);
};
auto solve_for_top = [&] {
top = solve_for(top.resolved(box, height_of_containing_block));
};
auto solve_for_bottom = [&] {
bottom = solve_for(bottom.resolved(box, height_of_containing_block));
};
auto solve_for_height = [&] {
height = CSS::Size::make_length(solve_for(height.resolved(box, height_of_containing_block), ClampToZero::Yes));
};
auto solve_for_margin_top = [&] {
margin_top = solve_for(margin_top.resolved(box, width_of_containing_block));
};
auto solve_for_margin_bottom = [&] {
margin_bottom = solve_for(margin_bottom.resolved(box, width_of_containing_block));
};
auto solve_for_margin_top_and_margin_bottom = [&] {
auto remainder = solve_for(CSS::Length::make_px(margin_top.to_px(box, width_of_containing_block) + margin_bottom.to_px(box, width_of_containing_block))).to_px(box);
margin_top = CSS::Length::make_px(remainder / 2);
margin_bottom = CSS::Length::make_px(remainder / 2);
};
// If all three of top, height, and bottom are auto:
if (top.is_auto() && should_treat_height_as_auto(box, available_space) && bottom.is_auto()) {
// First set any auto values for margin-top and margin-bottom to 0,
if (margin_top.is_auto())
margin_top = CSS::Length::make_px(0);
if (margin_bottom.is_auto())
margin_bottom = CSS::Length::make_px(0);
// then set top to the static position,
// and finally apply rule number three below.
// NOTE: We actually perform these two steps in the opposite order,
// because the static position may depend on the height of the box (due to alignment properties).
auto maybe_height = compute_auto_height_for_absolutely_positioned_element(box, available_space, before_or_after_inside_layout);
if (!maybe_height.has_value())
return;
height = CSS::Size::make_px(maybe_height.value());
auto constrained_height = apply_min_max_height_constraints(maybe_height.value());
m_state.get_mutable(box).set_content_height(constrained_height);
auto static_position = calculate_static_position(box);
top = CSS::Length::make_px(static_position.y());
solve_for_bottom();
}
// If none of the three are auto:
else if (!top.is_auto() && !should_treat_height_as_auto(box, available_space) && !bottom.is_auto()) {
// If both margin-top and margin-bottom are auto,
if (margin_top.is_auto() && margin_bottom.is_auto()) {
// solve the equation under the extra constraint that the two margins get equal values.
solve_for_margin_top_and_margin_bottom();
}
// If one of margin-top or margin-bottom is auto,
else if (margin_top.is_auto() || margin_bottom.is_auto()) {
// solve the equation for that value.
if (margin_top.is_auto())
solve_for_margin_top();
else
solve_for_margin_bottom();
}
// If the values are over-constrained,
else {
// ignore the value for bottom and solve for that value.
solve_for_bottom();
}
}
// Otherwise,
else {
// set auto values for margin-top and margin-bottom to 0,
if (margin_top.is_auto())
margin_top = CSS::Length::make_px(0);
if (margin_bottom.is_auto())
margin_bottom = CSS::Length::make_px(0);
// and pick one of the following six rules that apply.
// 1. If top and height are auto and bottom is not auto,
if (top.is_auto() && should_treat_height_as_auto(box, available_space) && !bottom.is_auto()) {
// then the height is based on the Auto heights for block formatting context roots,
auto maybe_height = compute_auto_height_for_absolutely_positioned_element(box, available_space, before_or_after_inside_layout);
if (!maybe_height.has_value())
return;
height = CSS::Size::make_px(maybe_height.value());
// and solve for top.
solve_for_top();
}
// 2. If top and bottom are auto and height is not auto,
else if (top.is_auto() && bottom.is_auto() && !should_treat_height_as_auto(box, available_space)) {
// then set top to the static position,
top = CSS::Length::make_px(calculate_static_position(box).y());
// then solve for bottom.
solve_for_bottom();
}
// 3. If height and bottom are auto and top is not auto,
else if (should_treat_height_as_auto(box, available_space) && bottom.is_auto() && !top.is_auto()) {
// then the height is based on the Auto heights for block formatting context roots,
auto maybe_height = compute_auto_height_for_absolutely_positioned_element(box, available_space, before_or_after_inside_layout);
if (!maybe_height.has_value())
return;
height = CSS::Size::make_px(maybe_height.value());
// and solve for bottom.
solve_for_bottom();
}
// 4. If top is auto, height and bottom are not auto,
else if (top.is_auto() && !should_treat_height_as_auto(box, available_space) && !bottom.is_auto()) {
// then solve for top.
solve_for_top();
}
// 5. If height is auto, top and bottom are not auto,
else if (should_treat_height_as_auto(box, available_space) && !top.is_auto() && !bottom.is_auto()) {
// then solve for height.
solve_for_height();
}
// 6. If bottom is auto, top and height are not auto,
else if (bottom.is_auto() && !top.is_auto() && !should_treat_height_as_auto(box, available_space)) {
// then solve for bottom.
solve_for_bottom();
}
}
// Compute the height based on box type and CSS properties:
// https://www.w3.org/TR/css-sizing-3/#box-sizing
CSSPixels used_height = 0;
if (should_treat_height_as_auto(box, available_space)) {
used_height = height.to_px(box, height_of_containing_block);
} else {
used_height = calculate_inner_height(box, available_space.height, height);
}
used_height = apply_min_max_height_constraints(used_height);
// NOTE: The following is not directly part of any spec, but this is where we resolve
// the final used values for vertical margin/border/padding.
auto& box_state = m_state.get_mutable(box);
box_state.set_content_height(used_height);
// do not set calculated insets or margins on the first pass, there will be a second pass
if (before_or_after_inside_layout == BeforeOrAfterInsideLayout::Before)
return;
box_state.inset_top = top.to_px(box, height_of_containing_block);
box_state.inset_bottom = bottom.to_px(box, height_of_containing_block);
box_state.margin_top = margin_top.to_px(box, width_of_containing_block);
box_state.margin_bottom = margin_bottom.to_px(box, width_of_containing_block);
box_state.padding_top = box.computed_values().padding().top().to_px(box, width_of_containing_block);
box_state.padding_bottom = box.computed_values().padding().bottom().to_px(box, width_of_containing_block);
}
// NOTE: This is different from content_box_rect_in_ancestor_coordinate_space() as this does *not* follow the containing block chain up, but rather the parent() chain.
CSSPixelRect FormattingContext::content_box_rect_in_static_position_ancestor_coordinate_space(Box const& box, Box const& ancestor_box) const
{
auto rect = content_box_rect(box);
if (&box == &ancestor_box)
return rect;
for (auto const* current = box.parent(); current; current = current->parent()) {
if (current == &ancestor_box)
return rect;
auto const& current_state = m_state.get(*current);
rect.translate_by(current_state.offset);
}
// If we get here, ancestor_box was not an ancestor of `box`!
VERIFY_NOT_REACHED();
}
// https://www.w3.org/TR/css-position-3/#staticpos-rect
CSSPixelPoint FormattingContext::calculate_static_position(Box const& box) const
{
// NOTE: This is very ad-hoc.
// The purpose of this function is to calculate the approximate position that `box`
// would have had if it were position:static.
CSSPixels x = 0;
CSSPixels y = 0;
VERIFY(box.parent());
if (box.parent()->children_are_inline()) {
// We're an abspos box with inline siblings. This is gonna get messy!
if (auto* sibling = box.previous_sibling()) {
// Hard case: there's a previous sibling. This means there's already inline content
// preceding the hypothetical static position of `box` within its containing block.
// If we had been position:static, that inline content would have been wrapped in
// anonymous block box, so now we get to imagine what the world might have looked like
// in that scenario..
// Basically, we find its last associated line box fragment and place `box` under it.
// FIXME: I'm 100% sure this can be smarter, better and faster.
LineBoxFragment const* last_fragment = nullptr;
auto& cb_state = m_state.get(*sibling->containing_block());
for (auto& line_box : cb_state.line_boxes) {
for (auto& fragment : line_box.fragments()) {
if (&fragment.layout_node() == sibling)
last_fragment = &fragment;
}
}
if (last_fragment) {
y = last_fragment->offset().y() + last_fragment->height();
}
} else {
// Easy case: no previous sibling, we're at the top of the containing block.
}
} else {
x = m_state.get(box).margin_left;
// We're among block siblings, Y can be calculated easily.
y = m_state.get(box).margin_top;
}
auto offset_to_static_parent = content_box_rect_in_static_position_ancestor_coordinate_space(box, *box.containing_block());
return offset_to_static_parent.location().translated(x, y);
}
void FormattingContext::layout_absolutely_positioned_element(Box const& box, AvailableSpace const& available_space)
{
auto& containing_block_state = m_state.get_mutable(*box.containing_block());
auto& box_state = m_state.get_mutable(box);
// The border computed values are not changed by the compute_height & width calculations below.
// The spec only adjusts and computes sizes, insets and margins.
box_state.border_left = box.computed_values().border_left().width;
box_state.border_right = box.computed_values().border_right().width;
box_state.border_top = box.computed_values().border_top().width;
box_state.border_bottom = box.computed_values().border_bottom().width;
compute_width_for_absolutely_positioned_element(box, available_space);
// NOTE: We compute height before *and* after doing inside layout.
// This is done so that inside layout can resolve percentage heights.
// In some situations, e.g with non-auto top & bottom values, the height can be determined early.
compute_height_for_absolutely_positioned_element(box, available_space, BeforeOrAfterInsideLayout::Before);
auto independent_formatting_context = layout_inside(box, LayoutMode::Normal, box_state.available_inner_space_or_constraints_from(available_space));
compute_height_for_absolutely_positioned_element(box, available_space, BeforeOrAfterInsideLayout::After);
CSSPixelPoint used_offset;
used_offset.set_x(box_state.inset_left + box_state.margin_box_left());
used_offset.set_y(box_state.inset_top + box_state.margin_box_top());
// NOTE: Absolutely positioned boxes are relative to the *padding edge* of the containing block.
// Padding offset only need to be compensated when top/left/bottom/right is not auto because otherwise
// the box is positioned at the static position of the containing block.
if (!box.computed_values().inset().top().is_auto() || !box.computed_values().inset().bottom().is_auto())
used_offset.translate_by(0, -containing_block_state.padding_top);
if (!box.computed_values().inset().left().is_auto() || !box.computed_values().inset().right().is_auto())
used_offset.translate_by(-containing_block_state.padding_left, 0);
box_state.set_content_offset(used_offset);
if (independent_formatting_context)
independent_formatting_context->parent_context_did_dimension_child_root_box();
}
void FormattingContext::compute_height_for_absolutely_positioned_replaced_element(Box const& box, AvailableSpace const& available_space, BeforeOrAfterInsideLayout before_or_after_inside_layout)
{
// 10.6.5 Absolutely positioned, replaced elements
// This situation is similar to 10.6.4, except that the element has an intrinsic height.
// The used value of 'height' is determined as for inline replaced elements.
auto height = compute_height_for_replaced_element(box, available_space);
auto height_of_containing_block = available_space.height.to_px_or_zero();
auto available = height_of_containing_block - height;
auto const& computed_values = box.computed_values();
auto top = computed_values.inset().top();
auto margin_top = computed_values.margin().top();
auto bottom = computed_values.inset().bottom();
auto margin_bottom = computed_values.margin().bottom();
auto static_position = calculate_static_position(box);
auto to_px = [&](const CSS::LengthPercentage& l) {
return l.to_px(box, height_of_containing_block);
};
// If 'margin-top' or 'margin-bottom' is specified as 'auto' its used value is determined by the rules below.
// 2. If both 'top' and 'bottom' have the value 'auto', replace 'top' with the element's static position.
if (top.is_auto() && bottom.is_auto()) {
top = CSS::Length::make_px(static_position.x());
}
// 3. If 'bottom' is 'auto', replace any 'auto' on 'margin-top' or 'margin-bottom' with '0'.
if (bottom.is_auto()) {
if (margin_top.is_auto())
margin_top = CSS::Length::make_px(0);
if (margin_bottom.is_auto())
margin_bottom = CSS::Length::make_px(0);
}
// 4. If at this point both 'margin-top' and 'margin-bottom' are still 'auto',
// solve the equation under the extra constraint that the two margins must get equal values.
if (margin_top.is_auto() && margin_bottom.is_auto()) {
auto remainder = available - to_px(top) - to_px(bottom);
margin_top = CSS::Length::make_px(remainder / 2);
margin_bottom = CSS::Length::make_px(remainder / 2);
}
// 5. If at this point there is an 'auto' left, solve the equation for that value.
if (top.is_auto()) {
top = CSS::Length::make_px(available - to_px(bottom) - to_px(margin_top) - to_px(margin_bottom));
} else if (bottom.is_auto()) {
bottom = CSS::Length::make_px(available - to_px(top) - to_px(margin_top) - to_px(margin_bottom));
} else if (margin_top.is_auto()) {
margin_top = CSS::Length::make_px(available - to_px(top) - to_px(bottom) - to_px(margin_bottom));
} else if (margin_bottom.is_auto()) {
margin_bottom = CSS::Length::make_px(available - to_px(top) - to_px(margin_top) - to_px(bottom));
}
// 6. If at this point the values are over-constrained, ignore the value for 'bottom' and solve for that value.
if (0 != available - to_px(top) - to_px(bottom) - to_px(margin_top) - to_px(margin_bottom)) {
bottom = CSS::Length::make_px(available - to_px(top) - to_px(margin_top) - to_px(margin_bottom));
}
auto& box_state = m_state.get_mutable(box);
box_state.set_content_height(height);
// do not set calculated insets or margins on the first pass, there will be a second pass
if (before_or_after_inside_layout == BeforeOrAfterInsideLayout::Before)
return;
box_state.inset_top = to_px(top);
box_state.inset_bottom = to_px(bottom);
box_state.margin_top = to_px(margin_top);
box_state.margin_bottom = to_px(margin_bottom);
}
// https://www.w3.org/TR/css-position-3/#relpos-insets
void FormattingContext::compute_inset(NodeWithStyleAndBoxModelMetrics const& box)
{
if (box.computed_values().position() != CSS::Positioning::Relative)
return;
auto resolve_two_opposing_insets = [&](CSS::LengthPercentage const& computed_first, CSS::LengthPercentage const& computed_second, CSSPixels& used_start, CSSPixels& used_end, CSSPixels reference_for_percentage) {
auto resolved_first = computed_first.to_px(box, reference_for_percentage);
auto resolved_second = computed_second.to_px(box, reference_for_percentage);
if (computed_first.is_auto() && computed_second.is_auto()) {
// If opposing inset properties in an axis both compute to auto (their initial values),
// their used values are zero (i.e., the boxes stay in their original position in that axis).
used_start = 0;
used_end = 0;
} else if (computed_first.is_auto() || computed_second.is_auto()) {
// If only one is auto, its used value becomes the negation of the other, and the box is shifted by the specified amount.
if (computed_first.is_auto()) {
used_end = resolved_second;
used_start = -used_end;
} else {
used_start = resolved_first;
used_end = -used_start;
}
} else {
// If neither is auto, the position is over-constrained; (with respect to the writing mode of its containing block)
// the computed end side value is ignored, and its used value becomes the negation of the start side.
used_start = resolved_first;
used_end = -used_start;
}
};
auto& box_state = m_state.get_mutable(box);
auto const& computed_values = box.computed_values();
// FIXME: Respect the containing block's writing-mode.
resolve_two_opposing_insets(computed_values.inset().left(), computed_values.inset().right(), box_state.inset_left, box_state.inset_right, containing_block_width_for(box));
resolve_two_opposing_insets(computed_values.inset().top(), computed_values.inset().bottom(), box_state.inset_top, box_state.inset_bottom, containing_block_height_for(box));
}
// https://drafts.csswg.org/css-sizing-3/#fit-content-size
CSSPixels FormattingContext::calculate_fit_content_width(Layout::Box const& box, AvailableSpace const& available_space) const
{
// If the available space in a given axis is definite,
// equal to clamp(min-content size, stretch-fit size, max-content size)
// (i.e. max(min-content size, min(max-content size, stretch-fit size))).
if (available_space.width.is_definite()) {
return max(calculate_min_content_width(box),
min(calculate_stretch_fit_width(box, available_space.width),
calculate_max_content_width(box)));
}
// When sizing under a min-content constraint, equal to the min-content size.
if (available_space.width.is_min_content())
return calculate_min_content_width(box);
// Otherwise, equal to the max-content size in that axis.
return calculate_max_content_width(box);
}
// https://drafts.csswg.org/css-sizing-3/#fit-content-size
CSSPixels FormattingContext::calculate_fit_content_height(Layout::Box const& box, AvailableSpace const& available_space) const
{
// If the available space in a given axis is definite,
// equal to clamp(min-content size, stretch-fit size, max-content size)
// (i.e. max(min-content size, min(max-content size, stretch-fit size))).
if (available_space.height.is_definite()) {
return max(calculate_min_content_height(box, available_space.width.to_px_or_zero()),
min(calculate_stretch_fit_height(box, available_space.height),
calculate_max_content_height(box, available_space.width.to_px_or_zero())));
}
// When sizing under a min-content constraint, equal to the min-content size.
if (available_space.height.is_min_content())
return calculate_min_content_height(box, available_space.width.to_px_or_zero());
// Otherwise, equal to the max-content size in that axis.
return calculate_max_content_height(box, available_space.width.to_px_or_zero());
}
CSSPixels FormattingContext::calculate_min_content_width(Layout::Box const& box) const
{
if (box.has_natural_width())
return *box.natural_width();
auto& root_state = m_state.m_root;
auto& cache = *root_state.intrinsic_sizes.ensure(&box, [] { return adopt_own(*new LayoutState::IntrinsicSizes); });
if (cache.min_content_width.has_value())
return *cache.min_content_width;
LayoutState throwaway_state(&m_state);
auto& box_state = throwaway_state.get_mutable(box);
box_state.width_constraint = SizeConstraint::MinContent;
box_state.set_indefinite_content_width();
box_state.set_indefinite_content_height();
auto context = const_cast<FormattingContext*>(this)->create_independent_formatting_context_if_needed(throwaway_state, box);
if (!context) {
context = make<BlockFormattingContext>(throwaway_state, verify_cast<BlockContainer>(box), nullptr);
}
auto available_width = AvailableSize::make_min_content();
auto available_height = AvailableSize::make_indefinite();
context->run(box, LayoutMode::IntrinsicSizing, AvailableSpace(available_width, available_height));
cache.min_content_width = context->automatic_content_width();
if (cache.min_content_width->might_be_saturated()) {
// HACK: If layout calculates a non-finite result, something went wrong. Force it to zero and log a little whine.
dbgln("FIXME: Calculated non-finite min-content width for {}", box.debug_description());
cache.min_content_width = 0;
}
return *cache.min_content_width;
}
CSSPixels FormattingContext::calculate_max_content_width(Layout::Box const& box) const
{
if (box.has_natural_width())
return *box.natural_width();
auto& root_state = m_state.m_root;
auto& cache = *root_state.intrinsic_sizes.ensure(&box, [] { return adopt_own(*new LayoutState::IntrinsicSizes); });
if (cache.max_content_width.has_value())
return *cache.max_content_width;
LayoutState throwaway_state(&m_state);
auto& box_state = throwaway_state.get_mutable(box);
box_state.width_constraint = SizeConstraint::MaxContent;
box_state.set_indefinite_content_width();
box_state.set_indefinite_content_height();
auto context = const_cast<FormattingContext*>(this)->create_independent_formatting_context_if_needed(throwaway_state, box);
if (!context) {
context = make<BlockFormattingContext>(throwaway_state, verify_cast<BlockContainer>(box), nullptr);
}
auto available_width = AvailableSize::make_max_content();
auto available_height = AvailableSize::make_indefinite();
context->run(box, LayoutMode::IntrinsicSizing, AvailableSpace(available_width, available_height));
cache.max_content_width = context->automatic_content_width();
if (cache.max_content_width->might_be_saturated()) {
// HACK: If layout calculates a non-finite result, something went wrong. Force it to zero and log a little whine.
dbgln("FIXME: Calculated non-finite max-content width for {}", box.debug_description());
cache.max_content_width = 0;
}
return *cache.max_content_width;
}
// https://www.w3.org/TR/css-sizing-3/#min-content-block-size
CSSPixels FormattingContext::calculate_min_content_height(Layout::Box const& box, CSSPixels width) const
{
// For block containers, tables, and inline boxes, this is equivalent to the max-content block size.
if (box.is_block_container() || box.display().is_table_inside())
return calculate_max_content_height(box, width);
if (box.has_natural_height())
return *box.natural_height();
auto get_cache_slot = [&]() -> Optional<CSSPixels>* {
auto& root_state = m_state.m_root;
auto& cache = *root_state.intrinsic_sizes.ensure(&box, [] { return adopt_own(*new LayoutState::IntrinsicSizes); });
return &cache.min_content_height.ensure(width);
};
if (auto* cache_slot = get_cache_slot(); cache_slot && cache_slot->has_value())
return cache_slot->value();
LayoutState throwaway_state(&m_state);
auto& box_state = throwaway_state.get_mutable(box);
box_state.height_constraint = SizeConstraint::MinContent;
box_state.set_indefinite_content_height();
box_state.set_content_width(width);
auto context = const_cast<FormattingContext*>(this)->create_independent_formatting_context_if_needed(throwaway_state, box);
if (!context) {
context = make<BlockFormattingContext>(throwaway_state, verify_cast<BlockContainer>(box), nullptr);
}
context->run(box, LayoutMode::IntrinsicSizing, AvailableSpace(AvailableSize::make_definite(width), AvailableSize::make_min_content()));
auto min_content_height = context->automatic_content_height();
if (min_content_height.might_be_saturated()) {
// HACK: If layout calculates a non-finite result, something went wrong. Force it to zero and log a little whine.
dbgln("FIXME: Calculated non-finite min-content height for {}", box.debug_description());
min_content_height = 0;
}
if (auto* cache_slot = get_cache_slot()) {
*cache_slot = min_content_height;
}
return min_content_height;
}
CSSPixels FormattingContext::calculate_max_content_height(Layout::Box const& box, CSSPixels width) const
{
if (box.has_preferred_aspect_ratio())
return width / *box.preferred_aspect_ratio();
if (box.has_natural_height())
return *box.natural_height();
auto get_cache_slot = [&]() -> Optional<CSSPixels>* {
auto& root_state = m_state.m_root;
auto& cache = *root_state.intrinsic_sizes.ensure(&box, [] { return adopt_own(*new LayoutState::IntrinsicSizes); });
return &cache.max_content_height.ensure(width);
};
if (auto* cache_slot = get_cache_slot(); cache_slot && cache_slot->has_value())
return cache_slot->value();
LayoutState throwaway_state(&m_state);
auto& box_state = throwaway_state.get_mutable(box);
box_state.height_constraint = SizeConstraint::MaxContent;
box_state.set_indefinite_content_height();
box_state.set_content_width(width);
auto context = const_cast<FormattingContext*>(this)->create_independent_formatting_context_if_needed(throwaway_state, box);
if (!context) {
context = make<BlockFormattingContext>(throwaway_state, verify_cast<BlockContainer>(box), nullptr);
}
context->run(box, LayoutMode::IntrinsicSizing, AvailableSpace(AvailableSize::make_definite(width), AvailableSize::make_max_content()));
auto max_content_height = context->automatic_content_height();
if (max_content_height.might_be_saturated()) {
// HACK: If layout calculates a non-finite result, something went wrong. Force it to zero and log a little whine.
dbgln("FIXME: Calculated non-finite max-content height for {}", box.debug_description());
max_content_height = 0;
}
if (auto* cache_slot = get_cache_slot()) {
*cache_slot = max_content_height;
}
return max_content_height;
}
CSSPixels FormattingContext::calculate_inner_width(Layout::Box const& box, AvailableSize const& available_width, CSS::Size const& width) const
{
VERIFY(!width.is_auto());
auto width_of_containing_block = available_width.to_px_or_zero();
if (width.is_fit_content()) {
return calculate_fit_content_width(box, AvailableSpace { available_width, AvailableSize::make_indefinite() });
}
if (width.is_max_content()) {
return calculate_max_content_width(box);
}
if (width.is_min_content()) {
return calculate_min_content_width(box);
}
auto& computed_values = box.computed_values();
if (computed_values.box_sizing() == CSS::BoxSizing::BorderBox) {
auto const padding_left = computed_values.padding().left().resolved(box, width_of_containing_block);
auto const padding_right = computed_values.padding().right().resolved(box, width_of_containing_block);
auto inner_width = width.to_px(box, width_of_containing_block)
- computed_values.border_left().width
- padding_left.to_px(box)
- computed_values.border_right().width
- padding_right.to_px(box);
return max(inner_width, 0);
}
return width.resolved(box, width_of_containing_block).to_px(box);
}
CSSPixels FormattingContext::calculate_inner_height(Layout::Box const& box, AvailableSize const&, CSS::Size const& height) const
{
VERIFY(!height.is_auto());
auto const* containing_block = box.non_anonymous_containing_block();
auto const& containing_block_state = m_state.get(*containing_block);
auto height_of_containing_block = containing_block_state.content_height();
if (box.computed_values().position() == CSS::Positioning::Absolute) {
// https://www.w3.org/TR/css-position-3/#def-cb
// If the box has position: absolute, then the containing block is formed by the padding edge of the ancestor
height_of_containing_block += containing_block_state.padding_top + containing_block_state.padding_bottom;
}
auto& computed_values = box.computed_values();
if (computed_values.box_sizing() == CSS::BoxSizing::BorderBox) {
auto width_of_containing_block = containing_block_width_for(box);
auto const padding_top = computed_values.padding().top().resolved(box, width_of_containing_block);
auto const padding_bottom = computed_values.padding().bottom().resolved(box, width_of_containing_block);
auto inner_height = height.to_px(box, height_of_containing_block)
- computed_values.border_top().width
- padding_top.to_px(box)
- computed_values.border_bottom().width
- padding_bottom.to_px(box);
return max(inner_height, 0);
}
return height.resolved(box, height_of_containing_block).to_px(box);
}
CSSPixels FormattingContext::containing_block_width_for(NodeWithStyleAndBoxModelMetrics const& node) const
{
auto const& containing_block_state = m_state.get(*node.containing_block());
auto const& node_state = m_state.get(node);
switch (node_state.width_constraint) {
case SizeConstraint::MinContent:
return 0;
case SizeConstraint::MaxContent:
return CSSPixels::max();
case SizeConstraint::None:
return containing_block_state.content_width();
}
VERIFY_NOT_REACHED();
}
CSSPixels FormattingContext::containing_block_height_for(NodeWithStyleAndBoxModelMetrics const& node) const
{
auto const& containing_block_state = m_state.get(*node.containing_block());
auto const& node_state = m_state.get(node);
switch (node_state.height_constraint) {
case SizeConstraint::MinContent:
return 0;
case SizeConstraint::MaxContent:
return CSSPixels::max();
case SizeConstraint::None:
return containing_block_state.content_height();
}
VERIFY_NOT_REACHED();
}
AvailableSize FormattingContext::containing_block_width_as_available_size(NodeWithStyleAndBoxModelMetrics const& node) const
{
auto const& containing_block_state = m_state.get(*node.containing_block());
auto const& node_state = m_state.get(node);
switch (node_state.width_constraint) {
case SizeConstraint::MinContent:
return AvailableSize::make_min_content();
case SizeConstraint::MaxContent:
return AvailableSize::make_max_content();
case SizeConstraint::None:
return AvailableSize::make_definite(containing_block_state.content_width());
}
VERIFY_NOT_REACHED();
}
AvailableSize FormattingContext::containing_block_height_as_available_size(NodeWithStyleAndBoxModelMetrics const& node) const
{
auto const& containing_block_state = m_state.get(*node.containing_block());
auto const& node_state = m_state.get(node);
switch (node_state.height_constraint) {
case SizeConstraint::MinContent:
return AvailableSize::make_min_content();
case SizeConstraint::MaxContent:
return AvailableSize::make_max_content();
case SizeConstraint::None:
return AvailableSize::make_definite(containing_block_state.content_height());
}
VERIFY_NOT_REACHED();
}
// https://drafts.csswg.org/css-sizing-3/#stretch-fit-size
CSSPixels FormattingContext::calculate_stretch_fit_width(Box const& box, AvailableSize const& available_width) const
{
// The size a box would take if its outer size filled the available space in the given axis;
// in other words, the stretch fit into the available space, if that is definite.
// Undefined if the available space is indefinite.
if (!available_width.is_definite())
return 0;
auto const& box_state = m_state.get(box);
return available_width.to_px_or_zero()
- box_state.margin_left
- box_state.margin_right
- box_state.padding_left
- box_state.padding_right
- box_state.border_left
- box_state.border_right;
}
// https://drafts.csswg.org/css-sizing-3/#stretch-fit-size
CSSPixels FormattingContext::calculate_stretch_fit_height(Box const& box, AvailableSize const& available_height) const
{
// The size a box would take if its outer size filled the available space in the given axis;
// in other words, the stretch fit into the available space, if that is definite.
// Undefined if the available space is indefinite.
auto const& box_state = m_state.get(box);
return available_height.to_px_or_zero()
- box_state.margin_top
- box_state.margin_bottom
- box_state.padding_top
- box_state.padding_bottom
- box_state.border_top
- box_state.border_bottom;
}
bool FormattingContext::should_treat_width_as_auto(Box const& box, AvailableSpace const& available_space)
{
if (box.computed_values().width().is_auto())
return true;
if (box.computed_values().width().contains_percentage()) {
if (available_space.width.is_max_content())
return true;
if (available_space.width.is_indefinite())
return true;
}
return false;
}
bool FormattingContext::should_treat_height_as_auto(Box const& box, AvailableSpace const& available_space)
{
auto computed_height = box.computed_values().height();
if (computed_height.is_auto())
return true;
// https://www.w3.org/TR/css-sizing-3/#valdef-width-min-content
// https://www.w3.org/TR/css-sizing-3/#valdef-width-max-content
// https://www.w3.org/TR/css-sizing-3/#valdef-width-fit-content
// For a box’s block size, unless otherwise specified, this is equivalent to its automatic size.
// FIXME: If height is not the block axis size, then we should be concerned with the width instead.
if (computed_height.is_min_content() || computed_height.is_max_content() || computed_height.is_fit_content())
return true;
if (box.computed_values().height().contains_percentage()) {
if (available_space.height.is_max_content())
return true;
if (available_space.height.is_indefinite())
return true;
}
return false;
}
bool FormattingContext::can_skip_is_anonymous_text_run(Box& box)
{
if (box.is_anonymous() && !box.is_generated() && !box.first_child_of_type<BlockContainer>()) {
bool contains_only_white_space = true;
box.for_each_in_subtree([&](auto const& node) {
if (!is<TextNode>(node) || !static_cast<TextNode const&>(node).dom_node().data().bytes_as_string_view().is_whitespace()) {
contains_only_white_space = false;
return IterationDecision::Break;
}
return IterationDecision::Continue;
});
if (contains_only_white_space)
return true;
}
return false;
}
CSSPixelRect FormattingContext::absolute_content_rect(Box const& box) const
{
auto const& box_state = m_state.get(box);
CSSPixelRect rect { box_state.offset, { box_state.content_width(), box_state.content_height() } };
for (auto* block = box_state.containing_block_used_values(); block; block = block->containing_block_used_values())
rect.translate_by(block->offset);
return rect;
}
Box const* FormattingContext::box_child_to_derive_baseline_from(Box const& box) const
{
if (!box.has_children() || box.children_are_inline())
return nullptr;
// To find the baseline of a box, we first look for the last in-flow child with at least one line box.
auto const* last_box_child = box.last_child_of_type<Box>();
for (Node const* child = last_box_child; child; child = child->previous_sibling()) {
if (!child->is_box())
continue;
auto& child_box = static_cast<Box const&>(*child);
if (!child_box.is_out_of_flow(*this) && !m_state.get(child_box).line_boxes.is_empty()) {
return &child_box;
}
auto box_child_to_derive_baseline_from_candidate = box_child_to_derive_baseline_from(child_box);
if (box_child_to_derive_baseline_from_candidate)
return box_child_to_derive_baseline_from_candidate;
}
// None of the children has a line box.
return nullptr;
}
CSSPixels FormattingContext::box_baseline(Box const& box) const
{
auto const& box_state = m_state.get(box);
// https://www.w3.org/TR/CSS2/visudet.html#propdef-vertical-align
auto const& vertical_align = box.computed_values().vertical_align();
if (vertical_align.has<CSS::VerticalAlign>()) {
switch (vertical_align.get<CSS::VerticalAlign>()) {
case CSS::VerticalAlign::Top:
// Top: Align the top of the aligned subtree with the top of the line box.
return box_state.border_box_top();
case CSS::VerticalAlign::Bottom:
// Bottom: Align the bottom of the aligned subtree with the bottom of the line box.
return box_state.content_height() + box_state.margin_box_top();
case CSS::VerticalAlign::TextTop:
// TextTop: Align the top of the box with the top of the parent's content area (see 10.6.1).
return box.computed_values().font_size();
case CSS::VerticalAlign::TextBottom:
// TextTop: Align the bottom of the box with the bottom of the parent's content area (see 10.6.1).
return box_state.content_height() - CSSPixels::nearest_value_for(box.containing_block()->first_available_font().pixel_metrics().descent * 2);
default:
break;
}
}
if (!box_state.line_boxes.is_empty())
return box_state.margin_box_top() + box_state.offset.y() + box_state.line_boxes.last().baseline();
if (auto const* child_box = box_child_to_derive_baseline_from(box)) {
return box_baseline(*child_box);
}
// If none of the children have a baseline set, the bottom margin edge of the box is used.
return box_state.margin_box_height();
}
CSSPixelRect FormattingContext::margin_box_rect(LayoutState::UsedValues const& used_values) const
{
return {
used_values.offset.translated(-used_values.margin_box_left(), -used_values.margin_box_top()),
{
used_values.margin_box_left() + used_values.content_width() + used_values.margin_box_right(),
used_values.margin_box_top() + used_values.content_height() + used_values.margin_box_bottom(),
},
};
}
CSSPixelRect FormattingContext::margin_box_rect(Box const& box) const
{
return margin_box_rect(m_state.get(box));
}
CSSPixelRect FormattingContext::border_box_rect(LayoutState::UsedValues const& used_values) const
{
return {
used_values.offset.translated(-used_values.border_box_left(), -used_values.border_box_top()),
{
used_values.border_box_left() + used_values.content_width() + used_values.border_box_right(),
used_values.border_box_top() + used_values.content_height() + used_values.border_box_bottom(),
},
};
}
CSSPixelRect FormattingContext::border_box_rect(Box const& box) const
{
return border_box_rect(m_state.get(box));
}
CSSPixelRect FormattingContext::border_box_rect_in_ancestor_coordinate_space(LayoutState::UsedValues const& used_values, Box const& ancestor_box) const
{
auto rect = border_box_rect(used_values);
if (&used_values.node() == &ancestor_box)
return rect;
for (auto const* current = used_values.containing_block_used_values(); current; current = current->containing_block_used_values()) {
if (&current->node() == &ancestor_box)
return rect;
rect.translate_by(current->offset);
}
// If we get here, ancestor_box was not a containing block ancestor of `box`!
VERIFY_NOT_REACHED();
}
CSSPixelRect FormattingContext::border_box_rect_in_ancestor_coordinate_space(Box const& box, Box const& ancestor_box) const
{
return border_box_rect_in_ancestor_coordinate_space(m_state.get(box), ancestor_box);
}
CSSPixelRect FormattingContext::content_box_rect(Box const& box) const
{
return content_box_rect(m_state.get(box));
}
CSSPixelRect FormattingContext::content_box_rect(LayoutState::UsedValues const& used_values) const
{
return CSSPixelRect { used_values.offset, { used_values.content_width(), used_values.content_height() } };
}
CSSPixelRect FormattingContext::content_box_rect_in_ancestor_coordinate_space(LayoutState::UsedValues const& used_values, Box const& ancestor_box) const
{
auto rect = content_box_rect(used_values);
if (&used_values.node() == &ancestor_box)
return rect;
for (auto const* current = used_values.containing_block_used_values(); current; current = current->containing_block_used_values()) {
if (&current->node() == &ancestor_box)
return rect;
rect.translate_by(current->offset);
}
// If we get here, ancestor_box was not a containing block ancestor of `box`!
VERIFY_NOT_REACHED();
}
CSSPixelRect FormattingContext::content_box_rect_in_ancestor_coordinate_space(Box const& box, Box const& ancestor_box) const
{
return content_box_rect_in_ancestor_coordinate_space(m_state.get(box), ancestor_box);
}
CSSPixelRect FormattingContext::margin_box_rect_in_ancestor_coordinate_space(LayoutState::UsedValues const& used_values, Box const& ancestor_box) const
{
auto rect = margin_box_rect(used_values);
if (&used_values.node() == &ancestor_box)
return rect;
for (auto const* current = used_values.containing_block_used_values(); current; current = current->containing_block_used_values()) {
if (&current->node() == &ancestor_box)
return rect;
rect.translate_by(current->offset);
}
// If we get here, ancestor_box was not a containing block ancestor of `box`!
VERIFY_NOT_REACHED();
}
CSSPixelRect FormattingContext::margin_box_rect_in_ancestor_coordinate_space(Box const& box, Box const& ancestor_box) const
{
return margin_box_rect_in_ancestor_coordinate_space(m_state.get(box), ancestor_box);
}
bool box_is_sized_as_replaced_element(Box const& box)
{
// When a box has a preferred aspect ratio, its automatic sizes are calculated the same as for a
// replaced element with a natural aspect ratio and no natural size in that axis, see e.g. CSS2 §10
// and CSS Flexible Box Model Level 1 §9.2.
// https://www.w3.org/TR/css-sizing-4/#aspect-ratio-automatic
return is<ReplacedBox>(box) || box.has_preferred_aspect_ratio();
}
bool FormattingContext::should_treat_max_width_as_none(Box const& box, AvailableSize const& available_width) const
{
auto const& max_width = box.computed_values().max_width();
if (max_width.is_none())
return true;
if (box.is_absolutely_positioned())
return false;
if (max_width.contains_percentage()) {
if (available_width.is_max_content())
return true;
if (available_width.is_min_content())
return false;
if (!m_state.get(*box.non_anonymous_containing_block()).has_definite_width())
return true;
}
if (box.children_are_inline()) {
if (max_width.is_fit_content() && available_width.is_intrinsic_sizing_constraint())
return true;
if (max_width.is_max_content() && available_width.is_max_content())
return true;
if (max_width.is_min_content() && available_width.is_min_content())
return true;
}
return false;
}
bool FormattingContext::should_treat_max_height_as_none(Box const& box, AvailableSize const& available_height) const
{
// https://www.w3.org/TR/CSS22/visudet.html#min-max-heights
// If the height of the containing block is not specified explicitly (i.e., it depends on content height),
// and this element is not absolutely positioned, the percentage value is treated as '0' (for 'min-height')
// or 'none' (for 'max-height').
auto const& max_height = box.computed_values().max_height();
if (max_height.is_none())
return true;
if (box.is_absolutely_positioned())
return false;
if (max_height.contains_percentage()) {
if (available_height.is_min_content())
return false;
if (!m_state.get(*box.non_anonymous_containing_block()).has_definite_height())
return true;
}
return false;
}
}
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