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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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73
Userland/Libraries/LibWeb/Layout/InlineFormattingContext.cpp
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2020-2022, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -11,6 +11,7 @@
#include <LibWeb/Layout/BlockFormattingContext.h>
#include <LibWeb/Layout/Box.h>
#include <LibWeb/Layout/InlineFormattingContext.h>
#include <LibWeb/Layout/InlineLevelIterator.h>
#include <LibWeb/Layout/ReplacedBox.h>
namespace Web::Layout {
@ -74,25 +75,17 @@ float InlineFormattingContext::available_width_at_line(size_t line_index) const
void InlineFormattingContext::run(Box&, LayoutMode layout_mode)
{
VERIFY(containing_block().children_are_inline());
containing_block().line_boxes().clear();
generate_line_boxes(layout_mode);
containing_block().for_each_child([&](auto& child) {
VERIFY(child.is_inline());
if (is<Box>(child) && child.is_absolutely_positioned()) {
layout_absolutely_positioned_element(verify_cast<Box>(child));
return;
}
child.split_into_lines(*this, layout_mode);
});
for (auto& line_box : containing_block().line_boxes()) {
line_box.trim_trailing_whitespace();
}
// If there's an empty line box at the bottom, just remove it instead of giving it height.
if (!containing_block().line_boxes().is_empty() && containing_block().line_boxes().last().fragments().is_empty())
containing_block().line_boxes().take_last();
auto text_align = containing_block().computed_values().text_align();
float min_line_height = containing_block().line_height();
float content_height = 0;
@ -234,4 +227,60 @@ void InlineFormattingContext::dimension_box_on_line(Box& box, LayoutMode layout_
dump_tree(box);
}
void InlineFormattingContext::generate_line_boxes(LayoutMode layout_mode)
{
auto& line_boxes = containing_block().line_boxes();
line_boxes.clear();
containing_block().ensure_last_line_box();
InlineLevelIterator iterator(containing_block(), layout_mode);
float available_width = containing_block().width();
for (;;) {
auto item_opt = iterator.next(available_width);
if (!item_opt.has_value())
break;
auto& item = item_opt.value();
float current_line_width = line_boxes.last().width();
bool should_break_here = layout_mode == LayoutMode::AllPossibleLineBreaks || (current_line_width + item.width) > available_width;
if (should_break_here)
line_boxes.append(LineBox());
if (item.type == InlineLevelIterator::Item::Type::ForcedBreak) {
line_boxes.append(LineBox());
continue;
}
if (item.type == InlineLevelIterator::Item::Type::Element) {
auto& box = verify_cast<Layout::Box>(*item.node);
dimension_box_on_line(box, LayoutMode::Default);
line_boxes.last().add_fragment(box, 0, 0, box.width(), box.height());
continue;
}
if (item.type == InlineLevelIterator::Item::Type::Text) {
auto& text_node = verify_cast<Layout::TextNode>(*item.node);
line_boxes.last().add_fragment(
text_node,
item.offset_in_node,
item.length_in_node,
item.width,
text_node.font().glyph_height());
continue;
}
}
for (auto& line_box : containing_block().line_boxes()) {
line_box.trim_trailing_whitespace();
}
// If there's an empty line box at the bottom, just remove it instead of giving it height.
if (!containing_block().line_boxes().is_empty() && containing_block().line_boxes().last().fragments().is_empty())
containing_block().line_boxes().take_last();
}
}