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ladybird/Libraries/LibWeb/Layout/TreeBuilder.cpp
Jelle Raaijmakers 336684bc5c LibWeb: Support inserting non-inline elements into inline elements 
Our layout tree requires that all containers either have inline or
non-inline children. In order to support the layout of non-inline
elements inside inline elements, we need to do a bit of tree
restructuring. It effectively simulates temporarily closing all inline
nodes, appending the block element, and resumes appending to the last
open inline node.

The acid1.txt expectation needed to be updated to reflect the fact that
we now hoist its <p> elements out of the inline <form> they were in.
Visually, the before and after situations for acid1.html are identical.
2025-01-23 09:33:10 +01:00

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/*
* Copyright (c) 2018-2022, Andreas Kling <andreas@ladybird.org>
* Copyright (c) 2022-2023, Sam Atkins <atkinssj@serenityos.org>
* Copyright (c) 2022, MacDue <macdue@dueutil.tech>
* Copyright (c) 2025, Jelle Raaijmakers <jelle@ladybird.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Optional.h>
#include <AK/TemporaryChange.h>
#include <LibWeb/CSS/StyleComputer.h>
#include <LibWeb/CSS/StyleValues/DisplayStyleValue.h>
#include <LibWeb/CSS/StyleValues/PercentageStyleValue.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/DOM/Element.h>
#include <LibWeb/DOM/ParentNode.h>
#include <LibWeb/DOM/ShadowRoot.h>
#include <LibWeb/Dump.h>
#include <LibWeb/HTML/HTMLInputElement.h>
#include <LibWeb/HTML/HTMLLIElement.h>
#include <LibWeb/HTML/HTMLOListElement.h>
#include <LibWeb/HTML/HTMLSlotElement.h>
#include <LibWeb/Layout/FieldSetBox.h>
#include <LibWeb/Layout/ListItemBox.h>
#include <LibWeb/Layout/ListItemMarkerBox.h>
#include <LibWeb/Layout/Node.h>
#include <LibWeb/Layout/SVGClipBox.h>
#include <LibWeb/Layout/SVGMaskBox.h>
#include <LibWeb/Layout/TableGrid.h>
#include <LibWeb/Layout/TableWrapper.h>
#include <LibWeb/Layout/TextNode.h>
#include <LibWeb/Layout/TreeBuilder.h>
#include <LibWeb/Layout/Viewport.h>
#include <LibWeb/SVG/SVGForeignObjectElement.h>
namespace Web::Layout {
TreeBuilder::TreeBuilder() = default;
static bool has_inline_or_in_flow_block_children(Layout::Node const& layout_node)
{
for (auto child = layout_node.first_child(); child; child = child->next_sibling()) {
if (child->is_inline() || child->is_in_flow())
return true;
}
return false;
}
static bool has_in_flow_block_children(Layout::Node const& layout_node)
{
if (layout_node.children_are_inline())
return false;
for (auto child = layout_node.first_child(); child; child = child->next_sibling()) {
if (child->is_inline())
continue;
if (child->is_in_flow())
return true;
}
return false;
}
// The insertion_parent_for_*() functions maintain the invariant that the in-flow children of
// block-level boxes must be either all block-level or all inline-level.
static Layout::Node& insertion_parent_for_inline_node(Layout::NodeWithStyle& layout_parent)
{
auto last_child_creating_anonymous_wrapper_if_needed = [](auto& layout_parent) -> Layout::Node& {
if (!layout_parent.last_child()
|| !layout_parent.last_child()->is_anonymous()
|| !layout_parent.last_child()->children_are_inline()
|| layout_parent.last_child()->is_generated()) {
layout_parent.append_child(layout_parent.create_anonymous_wrapper());
}
return *layout_parent.last_child();
};
if (is<FieldSetBox>(layout_parent))
return last_child_creating_anonymous_wrapper_if_needed(layout_parent);
if (layout_parent.display().is_inline_outside() && layout_parent.display().is_flow_inside())
return layout_parent;
if (layout_parent.display().is_flex_inside() || layout_parent.display().is_grid_inside())
return last_child_creating_anonymous_wrapper_if_needed(layout_parent);
if (!has_in_flow_block_children(layout_parent) || layout_parent.children_are_inline())
return layout_parent;
// Parent has block-level children, insert into an anonymous wrapper block (and create it first if needed)
return last_child_creating_anonymous_wrapper_if_needed(layout_parent);
}
static Layout::Node& insertion_parent_for_block_node(Layout::NodeWithStyle& layout_parent, Layout::Node& layout_node)
{
// Inline is fine for in-flow block children; we'll maintain the (non-)inline invariant after insertion.
if (layout_parent.is_inline() && layout_parent.display().is_flow_inside() && !layout_node.is_out_of_flow())
return layout_parent;
if (!has_inline_or_in_flow_block_children(layout_parent)) {
// Parent block has no children, insert this block into parent.
return layout_parent;
}
if (layout_node.is_out_of_flow()
&& !layout_parent.display().is_flex_inside()
&& !layout_parent.display().is_grid_inside()
&& !layout_parent.last_child()->is_generated()
&& layout_parent.last_child()->is_anonymous()
&& layout_parent.last_child()->children_are_inline()) {
// Block is out-of-flow & previous sibling was wrapped in an anonymous block.
// Join the previous sibling inside the anonymous block.
return *layout_parent.last_child();
}
if (!layout_parent.children_are_inline()) {
// Parent block has block-level children, insert this block into parent.
return layout_parent;
}
if (layout_node.is_out_of_flow()) {
// Block is out-of-flow, it can have inline siblings if necessary.
return layout_parent;
}
// Parent block has inline-level children (our siblings); wrap these siblings into an anonymous wrapper block.
Vector<GC::Ref<Node>> children;
for (GC::Ptr<Node> child = layout_parent.first_child(); child; child = child->next_sibling()) {
// NOTE: We let out-of-flow children stay in the parent, to preserve tree structure.
if (child->is_out_of_flow())
continue;
children.append(*child);
}
auto wrapper = layout_parent.create_anonymous_wrapper();
wrapper->set_children_are_inline(true);
for (auto child : children) {
layout_parent.remove_child(child);
wrapper->append_child(child);
}
layout_parent.set_children_are_inline(false);
layout_parent.append_child(wrapper);
// Then it's safe to insert this block into parent.
return layout_parent;
}
void TreeBuilder::insert_node_into_inline_or_block_ancestor(Layout::Node& node, CSS::Display display, AppendOrPrepend mode)
{
if (node.display().is_contents())
return;
// Find the nearest ancestor that can host the node.
auto& nearest_insertion_ancestor = [&]() -> NodeWithStyle& {
for (auto& ancestor : m_ancestor_stack.in_reverse()) {
auto const& ancestor_display = ancestor->display();
// Out-of-flow nodes cannot be hosted in inline flow nodes.
if (node.is_out_of_flow() && ancestor_display.is_inline_outside() && ancestor_display.is_flow_inside())
continue;
if (!ancestor_display.is_contents())
return ancestor;
}
VERIFY_NOT_REACHED();
}();
auto& insertion_point = display.is_inline_outside() ? insertion_parent_for_inline_node(nearest_insertion_ancestor)
: insertion_parent_for_block_node(nearest_insertion_ancestor, node);
if (mode == AppendOrPrepend::Prepend)
insertion_point.prepend_child(node);
else
insertion_point.append_child(node);
if (display.is_inline_outside()) {
// After inserting an inline-level box into a parent, mark the parent as having inline children.
insertion_point.set_children_are_inline(true);
} else if (node.is_in_flow()) {
// After inserting an in-flow block-level box into a parent, mark the parent as having non-inline children.
insertion_point.set_children_are_inline(false);
}
}
void TreeBuilder::create_pseudo_element_if_needed(DOM::Element& element, CSS::Selector::PseudoElement::Type pseudo_element, AppendOrPrepend mode)
{
auto& document = element.document();
auto pseudo_element_style = element.pseudo_element_computed_properties(pseudo_element);
if (!pseudo_element_style)
return;
auto initial_quote_nesting_level = m_quote_nesting_level;
auto [pseudo_element_content, final_quote_nesting_level] = pseudo_element_style->content(element, initial_quote_nesting_level);
m_quote_nesting_level = final_quote_nesting_level;
auto pseudo_element_display = pseudo_element_style->display();
// ::before and ::after only exist if they have content. `content: normal` computes to `none` for them.
// We also don't create them if they are `display: none`.
if (pseudo_element_display.is_none()
|| pseudo_element_content.type == CSS::ContentData::Type::Normal
|| pseudo_element_content.type == CSS::ContentData::Type::None)
return;
auto pseudo_element_node = DOM::Element::create_layout_node_for_display_type(document, pseudo_element_display, *pseudo_element_style, nullptr);
if (!pseudo_element_node)
return;
auto& style_computer = document.style_computer();
// FIXME: This code actually computes style for element::marker, and shouldn't for element::pseudo::marker
if (is<ListItemBox>(*pseudo_element_node)) {
auto marker_style = style_computer.compute_style(element, CSS::Selector::PseudoElement::Type::Marker);
auto list_item_marker = document.heap().allocate<ListItemMarkerBox>(
document,
pseudo_element_node->computed_values().list_style_type(),
pseudo_element_node->computed_values().list_style_position(),
0,
marker_style);
static_cast<ListItemBox&>(*pseudo_element_node).set_marker(list_item_marker);
element.set_pseudo_element_node({}, CSS::Selector::PseudoElement::Type::Marker, list_item_marker);
pseudo_element_node->append_child(*list_item_marker);
}
auto generated_for = Node::GeneratedFor::NotGenerated;
if (pseudo_element == CSS::Selector::PseudoElement::Type::Before) {
generated_for = Node::GeneratedFor::PseudoBefore;
} else if (pseudo_element == CSS::Selector::PseudoElement::Type::After) {
generated_for = Node::GeneratedFor::PseudoAfter;
} else {
VERIFY_NOT_REACHED();
}
pseudo_element_node->set_generated_for(generated_for, element);
pseudo_element_node->set_initial_quote_nesting_level(initial_quote_nesting_level);
// FIXME: Handle images, and multiple values
if (pseudo_element_content.type == CSS::ContentData::Type::String) {
auto text = document.realm().create<DOM::Text>(document, pseudo_element_content.data);
auto text_node = document.heap().allocate<Layout::TextNode>(document, *text);
text_node->set_generated_for(generated_for, element);
push_parent(*pseudo_element_node);
insert_node_into_inline_or_block_ancestor(*text_node, text_node->display(), AppendOrPrepend::Append);
pop_parent();
} else {
TODO();
}
element.set_pseudo_element_node({}, pseudo_element, pseudo_element_node);
insert_node_into_inline_or_block_ancestor(*pseudo_element_node, pseudo_element_display, mode);
pseudo_element_node->mutable_computed_values().set_content(pseudo_element_content);
}
// Block nodes inside inline nodes are allowed, but to maintain the invariant that either all layout children are
// inline or non-inline, we need to rearrange the tree a bit. All inline ancestors up to the node we've inserted are
// wrapped in an anonymous block, which is inserted into the nearest non-inline ancestor. We then recreate the inline
// ancestors in another anonymous block inserted after the node so we can continue adding children.
//
// Effectively, we try to turn this:
//
// InlineNode 1
// TextNode 1
// InlineNode N
// TextNode N
// BlockContainer (node)
//
// Into this:
//
// BlockContainer (anonymous "before")
// InlineNode 1
// TextNode 1
// InlineNode N
// TextNode N
// BlockContainer (anonymous "middle") continuation
// BlockContainer (node)
// BlockContainer (anonymous "after")
// InlineNode 1 continuation
// InlineNode N
//
// To be able to reconstruct their relation after restructuring, layout nodes keep track of their continuation. The
// top-most inline node of the "after" wrapper points to the "middle" wrapper, which points to the top-most inline node
// of the "before" wrapper. All other inline nodes in the "after" wrapper point to their counterparts in the "before"
// wrapper, to make it easier to create the right paintables since a DOM::Node only has a single Layout::Node.
//
// Appending then continues in the "after" tree. If a new block node is then inserted, we can reuse the "middle" wrapper
// if no inline siblings exist for node or its ancestors, and leave the existing "after" wrapper alone. Otherwise, we
// create new wrappers and extend the continuation chain.
//
// Inspired by: https://webkit.org/blog/115/webcore-rendering-ii-blocks-and-inlines/
void TreeBuilder::restructure_block_node_in_inline_parent(NodeWithStyleAndBoxModelMetrics& node)
{
// Mark parent as inline again
auto& parent = *node.parent();
VERIFY(!parent.children_are_inline());
parent.set_children_are_inline(true);
// Find nearest non-inline, content supporting ancestor that is not an anonymous block.
auto& nearest_block_ancestor = [&] -> NodeWithStyle& {
for (auto* ancestor = parent.parent(); ancestor; ancestor = ancestor->parent()) {
if (!ancestor->is_inline() && !ancestor->display().is_contents() && !ancestor->is_anonymous())
return *ancestor;
}
VERIFY_NOT_REACHED();
}();
nearest_block_ancestor.set_children_are_inline(false);
// Unwind the ancestor stack to find the topmost inline ancestor.
GC::Ptr<NodeWithStyleAndBoxModelMetrics> topmost_inline_ancestor;
for (auto* ancestor = &parent; ancestor; ancestor = ancestor->parent()) {
if (ancestor == &nearest_block_ancestor)
break;
if (ancestor == m_ancestor_stack.last())
m_ancestor_stack.take_last();
if (ancestor->is_inline())
topmost_inline_ancestor = static_cast<NodeWithStyleAndBoxModelMetrics*>(ancestor);
}
VERIFY(topmost_inline_ancestor);
// We need to host the topmost inline ancestor and its previous siblings in an anonymous "before" wrapper. If an
// inline wrapper does not already exist, we create a new one and add it to the nearest block ancestor.
GC::Ptr<Node> before_wrapper;
if (auto last_child = nearest_block_ancestor.last_child(); last_child->is_anonymous() && last_child->children_are_inline()) {
before_wrapper = last_child;
} else {
before_wrapper = nearest_block_ancestor.create_anonymous_wrapper();
before_wrapper->set_children_are_inline(true);
nearest_block_ancestor.append_child(*before_wrapper);
}
if (topmost_inline_ancestor->parent() != before_wrapper.ptr()) {
GC::Ptr<Node> inline_to_move = topmost_inline_ancestor;
while (inline_to_move) {
auto* next = inline_to_move->previous_sibling();
inline_to_move->remove();
before_wrapper->insert_before(*inline_to_move, before_wrapper->first_child());
inline_to_move = next;
}
}
// If we are part of an existing continuation and all inclusive ancestors have no previous siblings, we can reuse
// the existing middle wrapper. Otherwiser, we create a new middle wrapper to contain the block node and add it to
// the nearest block ancestor.
bool needs_new_continuation = true;
GC::Ptr<NodeWithStyleAndBoxModelMetrics> middle_wrapper;
if (topmost_inline_ancestor->continuation_of_node()) {
needs_new_continuation = false;
for (GC::Ptr<Node> ancestor = node; ancestor != topmost_inline_ancestor; ancestor = ancestor->parent()) {
if (ancestor->previous_sibling()) {
needs_new_continuation = true;
break;
}
}
if (!needs_new_continuation)
middle_wrapper = topmost_inline_ancestor->continuation_of_node();
}
if (!middle_wrapper) {
middle_wrapper = static_cast<NodeWithStyleAndBoxModelMetrics&>(*nearest_block_ancestor.create_anonymous_wrapper());
nearest_block_ancestor.append_child(*middle_wrapper);
middle_wrapper->set_continuation_of_node({}, topmost_inline_ancestor);
}
// Move the block node to the middle wrapper.
node.remove();
middle_wrapper->append_child(node);
// If we need a new continuation, recreate inline ancestors in another anonymous block so we can continue adding new
// nodes. We don't need to do this if we are within an existing continuation and there were no previous siblings in
// any inclusive ancestor of node in the after wrapper.
if (needs_new_continuation) {
auto after_wrapper = nearest_block_ancestor.create_anonymous_wrapper();
GC::Ptr<Node> current_parent = after_wrapper;
for (GC::Ptr<Node> inline_node = topmost_inline_ancestor;
inline_node && is<DOM::Element>(inline_node->dom_node()); inline_node = inline_node->last_child()) {
auto& element = static_cast<DOM::Element&>(*inline_node->dom_node());
auto style = element.computed_properties();
auto& new_inline_node = static_cast<NodeWithStyleAndBoxModelMetrics&>(*element.create_layout_node(*style));
if (inline_node == topmost_inline_ancestor) {
// The topmost inline ancestor points to the middle wrapper, which in turns points to the original node.
new_inline_node.set_continuation_of_node({}, middle_wrapper);
topmost_inline_ancestor = new_inline_node;
} else {
// We need all other inline nodes to point to their original node so we can walk the continuation chain
// in LayoutState and create the right paintables.
new_inline_node.set_continuation_of_node({}, static_cast<NodeWithStyleAndBoxModelMetrics&>(*inline_node));
}
current_parent->append_child(new_inline_node);
current_parent = new_inline_node;
// Stop recreating nodes when we've reached node's parent
if (inline_node == &parent)
break;
}
after_wrapper->set_children_are_inline(true);
nearest_block_ancestor.append_child(after_wrapper);
}
// Rewind the ancestor stack
for (GC::Ptr<Node> inline_node = topmost_inline_ancestor; inline_node; inline_node = inline_node->last_child()) {
if (!is<NodeWithStyle>(*inline_node))
break;
m_ancestor_stack.append(static_cast<NodeWithStyle&>(*inline_node));
}
}
static bool is_ignorable_whitespace(Layout::Node const& node)
{
if (node.is_text_node() && static_cast<TextNode const&>(node).text_for_rendering().bytes_as_string_view().is_whitespace())
return true;
if (node.is_anonymous() && node.is_block_container() && static_cast<BlockContainer const&>(node).children_are_inline()) {
bool contains_only_white_space = true;
node.for_each_in_inclusive_subtree_of_type<TextNode>([&contains_only_white_space](auto& text_node) {
if (!text_node.text_for_rendering().bytes_as_string_view().is_whitespace()) {
contains_only_white_space = false;
return TraversalDecision::Break;
}
return TraversalDecision::Continue;
});
if (contains_only_white_space)
return true;
}
return false;
}
i32 TreeBuilder::calculate_list_item_index(DOM::Node& dom_node)
{
if (is<HTML::HTMLLIElement>(dom_node)) {
auto& li = static_cast<HTML::HTMLLIElement&>(dom_node);
if (li.value() != 0)
return li.value();
}
if (dom_node.previous_sibling() != nullptr) {
DOM::Node* current = dom_node.previous_sibling();
while (current != nullptr) {
if (is<HTML::HTMLLIElement>(*current))
return calculate_list_item_index(*current) + 1;
current = current->previous_sibling();
}
}
if (is<HTML::HTMLOListElement>(*dom_node.parent())) {
auto& ol = static_cast<HTML::HTMLOListElement&>(*dom_node.parent());
return ol.start();
}
return 1;
}
void TreeBuilder::update_layout_tree(DOM::Node& dom_node, TreeBuilder::Context& context, MustCreateSubtree must_create_subtree)
{
bool should_create_layout_node = must_create_subtree == MustCreateSubtree::Yes
|| dom_node.needs_layout_tree_update()
|| dom_node.document().needs_full_layout_tree_update()
|| (dom_node.is_document() && !dom_node.layout_node());
if (dom_node.is_element()) {
auto& element = static_cast<DOM::Element&>(dom_node);
if (element.in_top_layer() && !context.layout_top_layer)
return;
}
if (dom_node.is_element())
dom_node.document().style_computer().push_ancestor(static_cast<DOM::Element const&>(dom_node));
ScopeGuard pop_ancestor_guard = [&] {
if (dom_node.is_element())
dom_node.document().style_computer().pop_ancestor(static_cast<DOM::Element const&>(dom_node));
};
GC::Ptr<Layout::Node> old_layout_node = dom_node.layout_node();
GC::Ptr<Layout::Node> layout_node;
Optional<TemporaryChange<bool>> has_svg_root_change;
ScopeGuard remove_stale_layout_node_guard = [&] {
// If we didn't create a layout node for this DOM node,
// go through the DOM tree and remove any old layout & paint nodes since they are now all stale.
if (!layout_node) {
dom_node.for_each_in_inclusive_subtree([&](auto& node) {
node.set_needs_layout_tree_update(false);
node.set_child_needs_layout_tree_update(false);
node.detach_layout_node({});
node.clear_paintable();
if (is<DOM::Element>(node))
static_cast<DOM::Element&>(node).clear_pseudo_element_nodes({});
return TraversalDecision::Continue;
});
}
};
if (dom_node.is_svg_container()) {
has_svg_root_change.emplace(context.has_svg_root, true);
} else if (dom_node.requires_svg_container() && !context.has_svg_root) {
return;
}
auto& document = dom_node.document();
auto& style_computer = document.style_computer();
GC::Ptr<CSS::ComputedProperties> style;
CSS::Display display;
if (!should_create_layout_node) {
if (is<DOM::Element>(dom_node)) {
auto& element = static_cast<DOM::Element&>(dom_node);
style = element.computed_properties();
display = style->display();
}
layout_node = dom_node.layout_node();
} else {
if (is<DOM::Element>(dom_node)) {
auto& element = static_cast<DOM::Element&>(dom_node);
element.clear_pseudo_element_nodes({});
VERIFY(!element.needs_style_update());
style = element.computed_properties();
element.resolve_counters(*style);
display = style->display();
if (display.is_none())
return;
// TODO: Implement changing element contents with the `content` property.
if (context.layout_svg_mask_or_clip_path) {
if (is<SVG::SVGMaskElement>(dom_node))
layout_node = document.heap().allocate<Layout::SVGMaskBox>(document, static_cast<SVG::SVGMaskElement&>(dom_node), *style);
else if (is<SVG::SVGClipPathElement>(dom_node))
layout_node = document.heap().allocate<Layout::SVGClipBox>(document, static_cast<SVG::SVGClipPathElement&>(dom_node), *style);
else
VERIFY_NOT_REACHED();
// Only layout direct uses of SVG masks/clipPaths.
context.layout_svg_mask_or_clip_path = false;
} else {
layout_node = element.create_layout_node(*style);
}
} else if (is<DOM::Document>(dom_node)) {
style = style_computer.create_document_style();
display = style->display();
layout_node = document.heap().allocate<Layout::Viewport>(static_cast<DOM::Document&>(dom_node), *style);
} else if (is<DOM::Text>(dom_node)) {
layout_node = document.heap().allocate<Layout::TextNode>(document, static_cast<DOM::Text&>(dom_node));
display = CSS::Display(CSS::DisplayOutside::Inline, CSS::DisplayInside::Flow);
}
}
if (!layout_node)
return;
if (dom_node.is_document()) {
m_layout_root = layout_node;
} else if (should_create_layout_node) {
// Decide whether to replace an existing node (partial tree update) or insert a new one appropriately.
bool const may_replace_existing_layout_node = must_create_subtree == MustCreateSubtree::No
&& old_layout_node
&& old_layout_node->parent()
&& old_layout_node != layout_node;
if (may_replace_existing_layout_node) {
old_layout_node->parent()->replace_child(*layout_node, *old_layout_node);
} else {
if (layout_node->is_svg_box()) {
m_ancestor_stack.last()->append_child(*layout_node);
} else {
insert_node_into_inline_or_block_ancestor(*layout_node, display, AppendOrPrepend::Append);
}
}
}
auto shadow_root = is<DOM::Element>(dom_node) ? as<DOM::Element>(dom_node).shadow_root() : nullptr;
auto element_has_content_visibility_hidden = [&dom_node]() {
if (is<DOM::Element>(dom_node)) {
auto& element = static_cast<DOM::Element&>(dom_node);
return element.computed_properties()->content_visibility() == CSS::ContentVisibility::Hidden;
}
return false;
}();
if (should_create_layout_node)
update_layout_tree_before_children(dom_node, *layout_node, context, element_has_content_visibility_hidden);
if (should_create_layout_node || dom_node.child_needs_layout_tree_update()) {
if ((dom_node.has_children() || shadow_root) && layout_node->can_have_children() && !element_has_content_visibility_hidden) {
push_parent(as<NodeWithStyle>(*layout_node));
if (shadow_root) {
for (auto* node = shadow_root->first_child(); node; node = node->next_sibling()) {
update_layout_tree(*node, context, should_create_layout_node ? MustCreateSubtree::Yes : MustCreateSubtree::No);
}
shadow_root->set_child_needs_layout_tree_update(false);
shadow_root->set_needs_layout_tree_update(false);
} else {
// This is the same as as<DOM::ParentNode>(dom_node).for_each_child
for (auto* node = as<DOM::ParentNode>(dom_node).first_child(); node; node = node->next_sibling())
update_layout_tree(*node, context, should_create_layout_node ? MustCreateSubtree::Yes : MustCreateSubtree::No);
}
if (dom_node.is_document()) {
// Elements in the top layer do not lay out normally based on their position in the document; instead they
// generate boxes as if they were siblings of the root element.
TemporaryChange<bool> layout_mask(context.layout_top_layer, true);
for (auto const& top_layer_element : document.top_layer_elements())
update_layout_tree(top_layer_element, context, should_create_layout_node ? MustCreateSubtree::Yes : MustCreateSubtree::No);
}
pop_parent();
}
}
if (should_create_layout_node)
update_layout_tree_after_children(dom_node, *layout_node, context, element_has_content_visibility_hidden);
dom_node.set_needs_layout_tree_update(false);
dom_node.set_child_needs_layout_tree_update(false);
}
void TreeBuilder::update_layout_tree_before_children(DOM::Node& dom_node, GC::Ref<Layout::Node> layout_node, TreeBuilder::Context&, bool element_has_content_visibility_hidden)
{
// Add node for the ::before pseudo-element.
if (is<DOM::Element>(dom_node) && layout_node->can_have_children() && !element_has_content_visibility_hidden) {
auto& element = static_cast<DOM::Element&>(dom_node);
push_parent(as<NodeWithStyle>(*layout_node));
create_pseudo_element_if_needed(element, CSS::Selector::PseudoElement::Type::Before, AppendOrPrepend::Prepend);
pop_parent();
}
}
void TreeBuilder::update_layout_tree_after_children(DOM::Node& dom_node, GC::Ref<Layout::Node> layout_node, TreeBuilder::Context& context, bool element_has_content_visibility_hidden)
{
auto& document = dom_node.document();
auto& style_computer = document.style_computer();
auto display = layout_node->display();
if (is<ListItemBox>(*layout_node)) {
auto& element = static_cast<DOM::Element&>(dom_node);
auto marker_style = style_computer.compute_style(element, CSS::Selector::PseudoElement::Type::Marker);
auto list_item_marker = document.heap().allocate<ListItemMarkerBox>(document, layout_node->computed_values().list_style_type(), layout_node->computed_values().list_style_position(), calculate_list_item_index(dom_node), marker_style);
static_cast<ListItemBox&>(*layout_node).set_marker(list_item_marker);
element.set_pseudo_element_node({}, CSS::Selector::PseudoElement::Type::Marker, list_item_marker);
layout_node->append_child(*list_item_marker);
}
if (is<HTML::HTMLSlotElement>(dom_node)) {
auto& slot_element = static_cast<HTML::HTMLSlotElement&>(dom_node);
if (slot_element.computed_properties()->content_visibility() == CSS::ContentVisibility::Hidden)
return;
auto slottables = slot_element.assigned_nodes_internal();
push_parent(as<NodeWithStyle>(*layout_node));
for (auto const& slottable : slottables)
slottable.visit([&](auto& node) { update_layout_tree(node, context, MustCreateSubtree::Yes); });
pop_parent();
}
if (is<SVG::SVGGraphicsElement>(dom_node)) {
auto& graphics_element = static_cast<SVG::SVGGraphicsElement&>(dom_node);
// Create the layout tree for the SVG mask/clip paths as a child of the masked element.
// Note: This will create a new subtree for each use of the mask (so there's not a 1-to-1 mapping
// from DOM node to mask layout node). Each use of a mask may be laid out differently so this
// duplication is necessary.
auto layout_mask_or_clip_path = [&](GC::Ptr<SVG::SVGElement const> mask_or_clip_path) {
TemporaryChange<bool> layout_mask(context.layout_svg_mask_or_clip_path, true);
push_parent(as<NodeWithStyle>(*layout_node));
update_layout_tree(const_cast<SVG::SVGElement&>(*mask_or_clip_path), context, MustCreateSubtree::Yes);
pop_parent();
};
if (auto mask = graphics_element.mask())
layout_mask_or_clip_path(mask);
if (auto clip_path = graphics_element.clip_path())
layout_mask_or_clip_path(clip_path);
}
auto is_button_layout = [&] {
if (dom_node.is_html_button_element())
return true;
if (!dom_node.is_html_input_element())
return false;
// https://html.spec.whatwg.org/multipage/rendering.html#the-input-element-as-a-button
// An input element whose type attribute is in the Submit Button, Reset Button, or Button state, when it generates a CSS box, is expected to depict a button and use button layout
auto const& input_element = static_cast<HTML::HTMLInputElement const&>(dom_node);
if (input_element.is_button())
return true;
return false;
}();
// https://html.spec.whatwg.org/multipage/rendering.html#button-layout
// If the computed value of 'inline-size' is 'auto', then the used value is the fit-content inline size.
if (is_button_layout && dom_node.layout_node()->computed_values().width().is_auto()) {
auto& computed_values = as<NodeWithStyle>(*dom_node.layout_node()).mutable_computed_values();
computed_values.set_width(CSS::Size::make_fit_content());
}
// https://html.spec.whatwg.org/multipage/rendering.html#button-layout
// If the element is an input element, or if it is a button element and its computed value for
// 'display' is not 'inline-grid', 'grid', 'inline-flex', or 'flex', then the element's box has
// a child anonymous button content box with the following behaviors:
if (is_button_layout && !display.is_grid_inside() && !display.is_flex_inside()) {
auto& parent = *dom_node.layout_node();
// If the box does not overflow in the vertical axis, then it is centered vertically.
// FIXME: Only apply alignment when box overflows
auto flex_computed_values = parent.computed_values().clone_inherited_values();
auto& mutable_flex_computed_values = static_cast<CSS::MutableComputedValues&>(*flex_computed_values);
mutable_flex_computed_values.set_display(CSS::Display { CSS::DisplayOutside::Block, CSS::DisplayInside::Flex });
mutable_flex_computed_values.set_justify_content(CSS::JustifyContent::Center);
mutable_flex_computed_values.set_flex_direction(CSS::FlexDirection::Column);
mutable_flex_computed_values.set_height(CSS::Size::make_percentage(CSS::Percentage(100)));
mutable_flex_computed_values.set_min_height(parent.computed_values().min_height());
auto flex_wrapper = parent.heap().template allocate<BlockContainer>(parent.document(), nullptr, move(flex_computed_values));
auto content_box_computed_values = parent.computed_values().clone_inherited_values();
auto content_box_wrapper = parent.heap().template allocate<BlockContainer>(parent.document(), nullptr, move(content_box_computed_values));
content_box_wrapper->set_children_are_inline(parent.children_are_inline());
Vector<GC::Root<Node>> sequence;
for (auto child = parent.first_child(); child; child = child->next_sibling()) {
if (child->is_generated_for_before_pseudo_element())
continue;
sequence.append(*child);
}
for (auto& node : sequence) {
parent.remove_child(*node);
content_box_wrapper->append_child(*node);
}
flex_wrapper->append_child(*content_box_wrapper);
parent.append_child(*flex_wrapper);
parent.set_children_are_inline(false);
}
// Add nodes for the ::after pseudo-element.
if (is<DOM::Element>(dom_node) && layout_node->can_have_children() && !element_has_content_visibility_hidden) {
auto& element = static_cast<DOM::Element&>(dom_node);
push_parent(as<NodeWithStyle>(*layout_node));
create_pseudo_element_if_needed(element, CSS::Selector::PseudoElement::Type::After, AppendOrPrepend::Append);
pop_parent();
}
// If we completely finished inserting a block level element into an inline parent, we need to fix up the tree so
// that we can maintain the invariant that all children are either inline or non-inline. We can't do this earlier,
// because the restructuring adds new children after this node that become part of the ancestor stack.
auto* layout_parent = layout_node->parent();
if (layout_parent && layout_parent->display().is_inline_outside() && !display.is_contents()
&& !display.is_inline_outside() && layout_parent->display().is_flow_inside() && !layout_node->is_out_of_flow())
restructure_block_node_in_inline_parent(static_cast<NodeWithStyleAndBoxModelMetrics&>(*layout_node));
}
GC::Ptr<Layout::Node> TreeBuilder::build(DOM::Node& dom_node)
{
VERIFY(dom_node.is_document());
dom_node.document().style_computer().reset_ancestor_filter();
Context context;
m_quote_nesting_level = 0;
update_layout_tree(dom_node, context, MustCreateSubtree::No);
if (auto* root = dom_node.document().layout_node())
fixup_tables(*root);
return m_layout_root;
}
template<CSS::DisplayInternal internal, typename Callback>
void TreeBuilder::for_each_in_tree_with_internal_display(NodeWithStyle& root, Callback callback)
{
root.for_each_in_inclusive_subtree_of_type<Box>([&](auto& box) {
auto const display = box.display();
if (display.is_internal() && display.internal() == internal)
callback(box);
return TraversalDecision::Continue;
});
}
template<CSS::DisplayInside inside, typename Callback>
void TreeBuilder::for_each_in_tree_with_inside_display(NodeWithStyle& root, Callback callback)
{
root.for_each_in_inclusive_subtree_of_type<Box>([&](auto& box) {
auto const display = box.display();
if (display.is_outside_and_inside() && display.inside() == inside)
callback(box);
return TraversalDecision::Continue;
});
}
void TreeBuilder::fixup_tables(NodeWithStyle& root)
{
remove_irrelevant_boxes(root);
generate_missing_child_wrappers(root);
auto table_root_boxes = generate_missing_parents(root);
missing_cells_fixup(table_root_boxes);
}
void TreeBuilder::remove_irrelevant_boxes(NodeWithStyle& root)
{
// The following boxes are discarded as if they were display:none:
Vector<GC::Root<Node>> to_remove;
// Children of a table-column.
for_each_in_tree_with_internal_display<CSS::DisplayInternal::TableColumn>(root, [&](Box& table_column) {
table_column.for_each_child([&](auto& child) {
to_remove.append(child);
return IterationDecision::Continue;
});
});
// Children of a table-column-group which are not a table-column.
for_each_in_tree_with_internal_display<CSS::DisplayInternal::TableColumnGroup>(root, [&](Box& table_column_group) {
table_column_group.for_each_child([&](auto& child) {
if (!child.display().is_table_column())
to_remove.append(child);
return IterationDecision::Continue;
});
});
// FIXME:
// Anonymous inline boxes which contain only white space and are between two immediate siblings each of which is a table-non-root box.
// Anonymous inline boxes which meet all of the following criteria:
// - they contain only white space
// - they are the first and/or last child of a tabular container
// - whose immediate sibling, if any, is a table-non-root box
for (auto& box : to_remove)
box->parent()->remove_child(*box);
}
static bool is_table_track(CSS::Display display)
{
return display.is_table_row() || display.is_table_column();
}
static bool is_table_track_group(CSS::Display display)
{
// Unless explicitly mentioned otherwise, mentions of table-row-groups in this spec also encompass the specialized
// table-header-groups and table-footer-groups.
return display.is_table_row_group()
|| display.is_table_header_group()
|| display.is_table_footer_group()
|| display.is_table_column_group();
}
static bool is_proper_table_child(Node const& node)
{
auto const display = node.display();
return is_table_track_group(display) || is_table_track(display) || display.is_table_caption();
}
static bool is_not_proper_table_child(Node const& node)
{
if (!node.has_style())
return true;
return !is_proper_table_child(node);
}
static bool is_table_row(Node const& node)
{
return node.display().is_table_row();
}
static bool is_not_table_row(Node const& node)
{
if (!node.has_style())
return true;
return !is_table_row(node);
}
static bool is_table_cell(Node const& node)
{
return node.display().is_table_cell();
}
static bool is_not_table_cell(Node const& node)
{
if (!node.has_style())
return true;
return !is_table_cell(node);
}
template<typename Matcher, typename Callback>
static void for_each_sequence_of_consecutive_children_matching(NodeWithStyle& parent, Matcher matcher, Callback callback)
{
Vector<GC::Root<Node>> sequence;
auto sequence_is_all_ignorable_whitespace = [&]() -> bool {
for (auto& node : sequence) {
if (!is_ignorable_whitespace(*node))
return false;
}
return true;
};
for (auto child = parent.first_child(); child; child = child->next_sibling()) {
if (matcher(*child) || (!sequence.is_empty() && is_ignorable_whitespace(*child))) {
sequence.append(*child);
} else {
if (!sequence.is_empty()) {
if (!sequence_is_all_ignorable_whitespace())
callback(sequence, child);
sequence.clear();
}
}
}
if (!sequence.is_empty() && !sequence_is_all_ignorable_whitespace())
callback(sequence, nullptr);
}
template<typename WrapperBoxType>
static void wrap_in_anonymous(Vector<GC::Root<Node>>& sequence, Node* nearest_sibling, CSS::Display display)
{
VERIFY(!sequence.is_empty());
auto& parent = *sequence.first()->parent();
auto computed_values = parent.computed_values().clone_inherited_values();
static_cast<CSS::MutableComputedValues&>(*computed_values).set_display(display);
auto wrapper = parent.heap().template allocate<WrapperBoxType>(parent.document(), nullptr, move(computed_values));
for (auto& child : sequence) {
parent.remove_child(*child);
wrapper->append_child(*child);
}
wrapper->set_children_are_inline(parent.children_are_inline());
if (nearest_sibling)
parent.insert_before(*wrapper, *nearest_sibling);
else
parent.append_child(*wrapper);
}
void TreeBuilder::generate_missing_child_wrappers(NodeWithStyle& root)
{
// An anonymous table-row box must be generated around each sequence of consecutive children of a table-root box which are not proper table child boxes.
for_each_in_tree_with_inside_display<CSS::DisplayInside::Table>(root, [&](auto& parent) {
for_each_sequence_of_consecutive_children_matching(parent, is_not_proper_table_child, [&](auto sequence, auto nearest_sibling) {
wrap_in_anonymous<Box>(sequence, nearest_sibling, CSS::Display { CSS::DisplayInternal::TableRow });
});
});
// An anonymous table-row box must be generated around each sequence of consecutive children of a table-row-group box which are not table-row boxes.
for_each_in_tree_with_internal_display<CSS::DisplayInternal::TableRowGroup>(root, [&](auto& parent) {
for_each_sequence_of_consecutive_children_matching(parent, is_not_table_row, [&](auto& sequence, auto nearest_sibling) {
wrap_in_anonymous<Box>(sequence, nearest_sibling, CSS::Display { CSS::DisplayInternal::TableRow });
});
});
// Unless explicitly mentioned otherwise, mentions of table-row-groups in this spec also encompass the specialized
// table-header-groups and table-footer-groups.
for_each_in_tree_with_internal_display<CSS::DisplayInternal::TableHeaderGroup>(root, [&](auto& parent) {
for_each_sequence_of_consecutive_children_matching(parent, is_not_table_row, [&](auto& sequence, auto nearest_sibling) {
wrap_in_anonymous<Box>(sequence, nearest_sibling, CSS::Display { CSS::DisplayInternal::TableRow });
});
});
for_each_in_tree_with_internal_display<CSS::DisplayInternal::TableFooterGroup>(root, [&](auto& parent) {
for_each_sequence_of_consecutive_children_matching(parent, is_not_table_row, [&](auto& sequence, auto nearest_sibling) {
wrap_in_anonymous<Box>(sequence, nearest_sibling, CSS::Display { CSS::DisplayInternal::TableRow });
});
});
// An anonymous table-cell box must be generated around each sequence of consecutive children of a table-row box which are not table-cell boxes. !Testcase
for_each_in_tree_with_internal_display<CSS::DisplayInternal::TableRow>(root, [&](auto& parent) {
for_each_sequence_of_consecutive_children_matching(parent, is_not_table_cell, [&](auto& sequence, auto nearest_sibling) {
wrap_in_anonymous<BlockContainer>(sequence, nearest_sibling, CSS::Display { CSS::DisplayInternal::TableCell });
});
});
}
Vector<GC::Root<Box>> TreeBuilder::generate_missing_parents(NodeWithStyle& root)
{
Vector<GC::Root<Box>> table_roots_to_wrap;
root.for_each_in_inclusive_subtree_of_type<Box>([&](auto& parent) {
// An anonymous table-row box must be generated around each sequence of consecutive table-cell boxes whose parent is not a table-row.
if (is_not_table_row(parent)) {
for_each_sequence_of_consecutive_children_matching(parent, is_table_cell, [&](auto& sequence, auto nearest_sibling) {
wrap_in_anonymous<Box>(sequence, nearest_sibling, CSS::Display { CSS::DisplayInternal::TableRow });
});
}
// A table-row is misparented if its parent is neither a table-row-group nor a table-root box.
if (!parent.display().is_table_inside() && !is_proper_table_child(parent)) {
for_each_sequence_of_consecutive_children_matching(parent, is_table_row, [&](auto& sequence, auto nearest_sibling) {
wrap_in_anonymous<Box>(sequence, nearest_sibling, CSS::Display::from_short(parent.display().is_inline_outside() ? CSS::Display::Short::InlineTable : CSS::Display::Short::Table));
});
}
// A table-row-group, table-column-group, or table-caption box is misparented if its parent is not a table-root box.
if (!parent.display().is_table_inside() && !is_proper_table_child(parent)) {
for_each_sequence_of_consecutive_children_matching(parent, is_proper_table_child, [&](auto& sequence, auto nearest_sibling) {
wrap_in_anonymous<Box>(sequence, nearest_sibling, CSS::Display::from_short(parent.display().is_inline_outside() ? CSS::Display::Short::InlineTable : CSS::Display::Short::Table));
});
}
// An anonymous table-wrapper box must be generated around each table-root.
if (parent.display().is_table_inside()) {
if (parent.has_been_wrapped_in_table_wrapper()) {
VERIFY(parent.parent());
VERIFY(parent.parent()->is_table_wrapper());
return TraversalDecision::Continue;
}
table_roots_to_wrap.append(parent);
}
return TraversalDecision::Continue;
});
for (auto& table_box : table_roots_to_wrap) {
auto* nearest_sibling = table_box->next_sibling();
auto& parent = *table_box->parent();
auto wrapper_computed_values = table_box->computed_values().clone_inherited_values();
table_box->transfer_table_box_computed_values_to_wrapper_computed_values(*wrapper_computed_values);
if (parent.is_table_wrapper()) {
auto& existing_wrapper = static_cast<TableWrapper&>(parent);
existing_wrapper.set_computed_values(move(wrapper_computed_values));
continue;
}
auto wrapper = parent.heap().allocate<TableWrapper>(parent.document(), nullptr, move(wrapper_computed_values));
parent.remove_child(*table_box);
wrapper->append_child(*table_box);
if (nearest_sibling)
parent.insert_before(*wrapper, *nearest_sibling);
else
parent.append_child(*wrapper);
table_box->set_has_been_wrapped_in_table_wrapper(true);
}
return table_roots_to_wrap;
}
template<typename Matcher, typename Callback>
static void for_each_child_box_matching(Box& parent, Matcher matcher, Callback callback)
{
parent.for_each_child_of_type<Box>([&](Box& child_box) {
if (matcher(child_box))
callback(child_box);
return IterationDecision::Continue;
});
}
static void fixup_row(Box& row_box, TableGrid const& table_grid, size_t row_index)
{
for (size_t column_index = 0; column_index < table_grid.column_count(); ++column_index) {
if (table_grid.occupancy_grid().contains({ column_index, row_index }))
continue;
auto computed_values = row_box.computed_values().clone_inherited_values();
auto& mutable_computed_values = static_cast<CSS::MutableComputedValues&>(*computed_values);
mutable_computed_values.set_display(Web::CSS::Display { CSS::DisplayInternal::TableCell });
// Ensure that the cell (with zero content height) will have the same height as the row by setting vertical-align to middle.
mutable_computed_values.set_vertical_align(CSS::VerticalAlign::Middle);
auto cell_box = row_box.heap().template allocate<BlockContainer>(row_box.document(), nullptr, move(computed_values));
row_box.append_child(cell_box);
}
}
void TreeBuilder::missing_cells_fixup(Vector<GC::Root<Box>> const& table_root_boxes)
{
// Implements https://www.w3.org/TR/css-tables-3/#missing-cells-fixup.
for (auto& table_box : table_root_boxes) {
auto table_grid = TableGrid::calculate_row_column_grid(*table_box);
size_t row_index = 0;
for_each_child_box_matching(*table_box, TableGrid::is_table_row_group, [&](auto& row_group_box) {
for_each_child_box_matching(row_group_box, is_table_row, [&](auto& row_box) {
fixup_row(row_box, table_grid, row_index);
++row_index;
return IterationDecision::Continue;
});
});
for_each_child_box_matching(*table_box, is_table_row, [&](auto& row_box) {
fixup_row(row_box, table_grid, row_index);
++row_index;
return IterationDecision::Continue;
});
}
}
}
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