ladybird/Userland/Libraries/LibWeb/Layout/InlineLevelIterator.cpp
Andreas Kling c9700e100e LibWeb: Start making our layout system "transactional"
This patch adds a map of Layout::Node to FormattingState::NodeState.
Instead of updating layout nodes incrementally as layout progresses
through the formatting contexts, all updates are now written to the
corresponding NodeState instead.

At the end of layout, FormattingState::commit() is called, which
transfers all the values from the NodeState objects to the Node.

This will soon allow us to perform completely non-destructive layouts
which don't affect the tree.

Note that there are many imperfections here, and still many places
where we assign to the NodeState, but later read directly from the Node
instead. I'm just committing at this stage to make subsequent diffs
easier to understand.
2022-02-21 18:35:12 +01:00

256 lines
9.7 KiB
C++

/*
* Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibWeb/Layout/BreakNode.h>
#include <LibWeb/Layout/InlineFormattingContext.h>
#include <LibWeb/Layout/InlineLevelIterator.h>
#include <LibWeb/Layout/InlineNode.h>
#include <LibWeb/Layout/ListItemMarkerBox.h>
#include <LibWeb/Layout/ReplacedBox.h>
namespace Web::Layout {
InlineLevelIterator::InlineLevelIterator(Layout::InlineFormattingContext& inline_formatting_context, Layout::FormattingState& formatting_state, Layout::BlockContainer const& container, LayoutMode layout_mode)
: m_inline_formatting_context(inline_formatting_context)
, m_formatting_state(formatting_state)
, m_container(container)
, m_next_node(container.first_child())
, m_layout_mode(layout_mode)
{
skip_to_next();
}
void InlineLevelIterator::enter_node_with_box_model_metrics(Layout::NodeWithStyleAndBoxModelMetrics const& node)
{
if (!m_extra_leading_metrics.has_value())
m_extra_leading_metrics = ExtraBoxMetrics {};
// FIXME: It's really weird that *this* is where we assign box model metrics for these layout nodes..
auto& node_state = m_formatting_state.ensure(node);
auto const& container_state = m_formatting_state.get(m_container);
auto const& computed_values = node.computed_values();
node_state.margin_left = computed_values.margin().left.resolved(node, CSS::Length::make_px(container_state.content_width)).to_px(node);
node_state.border_left = computed_values.border_left().width;
node_state.padding_left = computed_values.padding().left.resolved(node, CSS::Length::make_px(container_state.content_width)).to_px(node);
m_extra_leading_metrics->margin += node_state.margin_left;
m_extra_leading_metrics->border += node_state.border_left;
m_extra_leading_metrics->padding += node_state.padding_left;
m_box_model_node_stack.append(node);
}
void InlineLevelIterator::exit_node_with_box_model_metrics()
{
if (!m_extra_trailing_metrics.has_value())
m_extra_trailing_metrics = ExtraBoxMetrics {};
auto& node = m_box_model_node_stack.last();
auto& node_state = m_formatting_state.ensure(node);
auto const& container_state = m_formatting_state.get(m_container);
auto const& computed_values = node.computed_values();
node_state.margin_right = computed_values.margin().right.resolved(node, CSS::Length::make_px(container_state.content_width)).to_px(node);
node_state.border_right = computed_values.border_right().width;
node_state.padding_right = computed_values.padding().right.resolved(node, CSS::Length::make_px(container_state.content_width)).to_px(node);
m_extra_trailing_metrics->margin += node_state.margin_right;
m_extra_trailing_metrics->border += node_state.border_right;
m_extra_trailing_metrics->padding += node_state.padding_right;
m_box_model_node_stack.take_last();
}
// This is similar to Layout::Node::next_in_pre_order() but will not descend into inline-block nodes.
Layout::Node const* InlineLevelIterator::next_inline_node_in_pre_order(Layout::Node const& current, Layout::Node const* stay_within)
{
if (current.first_child() && current.first_child()->is_inline() && !current.is_inline_block())
return current.first_child();
Layout::Node const* node = &current;
Layout::Node const* next = nullptr;
while (!(next = node->next_sibling())) {
node = node->parent();
// If node is the last node on the "box model node stack", pop it off.
if (!m_box_model_node_stack.is_empty()
&& &m_box_model_node_stack.last() == node) {
exit_node_with_box_model_metrics();
}
if (!node || node == stay_within)
return nullptr;
}
return next;
}
void InlineLevelIterator::compute_next()
{
if (m_next_node == nullptr)
return;
do {
m_next_node = next_inline_node_in_pre_order(*m_next_node, &m_container);
} while (m_next_node && !m_next_node->is_inline());
}
void InlineLevelIterator::skip_to_next()
{
if (m_next_node && is<Layout::NodeWithStyleAndBoxModelMetrics>(*m_next_node))
enter_node_with_box_model_metrics(static_cast<Layout::NodeWithStyleAndBoxModelMetrics const&>(*m_next_node));
m_current_node = m_next_node;
compute_next();
}
Optional<InlineLevelIterator::Item> InlineLevelIterator::next(float available_width)
{
if (!m_current_node)
return {};
if (is<Layout::TextNode>(*m_current_node)) {
auto& text_node = static_cast<Layout::TextNode const&>(*m_current_node);
if (!m_text_node_context.has_value()) {
auto& line_boxes = m_formatting_state.get(m_container).line_boxes;
bool previous_is_empty_or_ends_in_whitespace = line_boxes.is_empty() || line_boxes.last().is_empty_or_ends_in_whitespace();
enter_text_node(text_node, previous_is_empty_or_ends_in_whitespace);
}
auto chunk_opt = m_text_node_context->next_chunk;
if (!chunk_opt.has_value()) {
m_text_node_context = {};
skip_to_next();
return next(available_width);
}
m_text_node_context->next_chunk = m_text_node_context->chunk_iterator.next();
if (!m_text_node_context->next_chunk.has_value())
m_text_node_context->is_last_chunk = true;
auto& chunk = chunk_opt.value();
float chunk_width = text_node.font().width(chunk.view) + text_node.font().glyph_spacing();
Item item {
.type = Item::Type::Text,
.node = &text_node,
.offset_in_node = chunk.start,
.length_in_node = chunk.length,
.width = chunk_width,
.should_force_break = m_text_node_context->do_respect_linebreaks && chunk.has_breaking_newline,
.is_collapsible_whitespace = m_text_node_context->do_collapse && chunk.is_all_whitespace,
};
add_extra_box_model_metrics_to_item(item, m_text_node_context->is_first_chunk, m_text_node_context->is_last_chunk);
return item;
}
if (m_current_node->is_positioned()) {
skip_to_next();
return next(available_width);
}
if (is<Layout::BreakNode>(*m_current_node)) {
skip_to_next();
return Item {
.type = Item::Type::ForcedBreak,
};
}
if (is<Layout::ListItemMarkerBox>(*m_current_node)) {
skip_to_next();
return next(available_width);
}
if (!is<Layout::Box>(*m_current_node)) {
skip_to_next();
return next(available_width);
}
if (is<Layout::ReplacedBox>(*m_current_node)) {
auto& replaced_box = static_cast<Layout::ReplacedBox const&>(*m_current_node);
// FIXME: This const_cast is gross.
const_cast<Layout::ReplacedBox&>(replaced_box).prepare_for_replaced_layout();
}
auto& box = verify_cast<Layout::Box>(*m_current_node);
auto& box_state = m_formatting_state.get(box);
m_inline_formatting_context.dimension_box_on_line(box, m_layout_mode);
skip_to_next();
auto item = Item {
.type = Item::Type::Element,
.node = &box,
.offset_in_node = 0,
.length_in_node = 0,
.width = box_state.content_width,
.padding_start = box_state.padding_left,
.padding_end = box_state.padding_right,
.border_start = box_state.border_left,
.border_end = box_state.border_right,
.margin_start = box_state.margin_left,
.margin_end = box_state.margin_right,
};
add_extra_box_model_metrics_to_item(item, true, true);
return item;
}
void InlineLevelIterator::enter_text_node(Layout::TextNode const& text_node, bool previous_is_empty_or_ends_in_whitespace)
{
bool do_collapse = true;
bool do_wrap_lines = true;
bool do_respect_linebreaks = false;
if (text_node.computed_values().white_space() == CSS::WhiteSpace::Nowrap) {
do_collapse = true;
do_wrap_lines = false;
do_respect_linebreaks = false;
} else if (text_node.computed_values().white_space() == CSS::WhiteSpace::Pre) {
do_collapse = false;
do_wrap_lines = false;
do_respect_linebreaks = true;
} else if (text_node.computed_values().white_space() == CSS::WhiteSpace::PreLine) {
do_collapse = true;
do_wrap_lines = true;
do_respect_linebreaks = true;
} else if (text_node.computed_values().white_space() == CSS::WhiteSpace::PreWrap) {
do_collapse = false;
do_wrap_lines = true;
do_respect_linebreaks = true;
}
// FIXME: The const_cast here is gross.
const_cast<TextNode&>(text_node).compute_text_for_rendering(do_collapse, previous_is_empty_or_ends_in_whitespace);
m_text_node_context = TextNodeContext {
.do_collapse = do_collapse,
.do_wrap_lines = do_wrap_lines,
.do_respect_linebreaks = do_respect_linebreaks,
.is_first_chunk = true,
.is_last_chunk = false,
.chunk_iterator = TextNode::ChunkIterator { text_node.text_for_rendering(), m_layout_mode, do_wrap_lines, do_respect_linebreaks },
};
m_text_node_context->next_chunk = m_text_node_context->chunk_iterator.next();
}
void InlineLevelIterator::add_extra_box_model_metrics_to_item(Item& item, bool add_leading_metrics, bool add_trailing_metrics)
{
if (add_leading_metrics && m_extra_leading_metrics.has_value()) {
item.margin_start += m_extra_leading_metrics->margin;
item.border_start += m_extra_leading_metrics->border;
item.padding_start += m_extra_leading_metrics->padding;
m_extra_leading_metrics = {};
}
if (add_trailing_metrics && m_extra_trailing_metrics.has_value()) {
item.margin_end += m_extra_trailing_metrics->margin;
item.border_end += m_extra_trailing_metrics->border;
item.padding_end += m_extra_trailing_metrics->padding;
m_extra_trailing_metrics = {};
}
}
}