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LibWeb: Add inline-level iterator that enumerates items for line layout

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This patch adds a new mechanism that allows InlineFormattingContext to
build line boxes incrementally instead of all-in-one go.

Incremental build will eventually allow much better support for CSS
floating objects.
This commit is contained in:
Andreas Kling 2022-01-17 15:07:19 +01:00
parent 9358f108c4
commit 1f603c54ff
6 changed files with 248 additions and 13 deletions
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117
Userland/Libraries/LibWeb/Layout/InlineLevelIterator.cpp Normal file
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/*
* Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibWeb/Layout/BreakNode.h>
#include <LibWeb/Layout/InlineLevelIterator.h>
#include <LibWeb/Layout/InlineNode.h>
#include <LibWeb/Layout/ReplacedBox.h>
namespace Web::Layout {
void InlineLevelIterator::skip_to_next()
{
VERIFY(m_current_node);
do {
m_current_node = m_current_node->next_in_pre_order(&m_container);
} while (m_current_node && !m_current_node->is_inline());
}
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&>(*m_current_node);
if (!m_text_node_context.has_value())
enter_text_node(text_node);
auto chunk_opt = m_text_node_context->chunk_iterator.next();
if (!chunk_opt.has_value()) {
m_text_node_context = {};
skip_to_next();
return next(available_width);
}
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,
};
return item;
}
if (is<Layout::BreakNode>(*m_current_node)) {
skip_to_next();
return Item {
.type = Item::Type::ForcedBreak,
};
}
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&>(*m_current_node);
replaced_box.prepare_for_replaced_layout();
}
auto& box = verify_cast<Layout::Box>(*m_current_node);
skip_to_next();
return Item {
.type = Item::Type::Element,
.node = &box,
.offset_in_node = 0,
.length_in_node = 0,
.width = box.width(),
};
}
void InlineLevelIterator::enter_text_node(Layout::TextNode& text_node)
{
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: Pass the correct value for the last boolean!
text_node.compute_text_for_rendering(do_collapse, true);
m_text_node_context = TextNodeContext {
.do_collapse = do_collapse,
.do_wrap_lines = do_wrap_lines,
.do_respect_linebreaks = do_respect_linebreaks,
.chunk_iterator = TextNode::ChunkIterator { text_node.text_for_rendering(), m_layout_mode, do_wrap_lines, do_respect_linebreaks },
};
}
}