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LibWeb: Start making our layout system "transactional"

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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.
This commit is contained in:
Andreas Kling 2022-02-20 15:51:24 +01:00
parent 561612f219
commit c9700e100e
27 changed files with 754 additions and 571 deletions
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73
Userland/Libraries/LibWeb/Layout/FormattingState.cpp Normal file
View file

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/*
* Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibWeb/Layout/BlockContainer.h>
#include <LibWeb/Layout/FormattingState.h>
namespace Web::Layout {
void FormattingState::commit()
{
for (auto& it : nodes) {
auto& node = const_cast<Layout::NodeWithStyleAndBoxModelMetrics&>(*it.key);
auto& node_state = *it.value;
// Transfer box model metrics.
node.box_model().offset = { node_state.offset_top, node_state.offset_right, node_state.offset_bottom, node_state.offset_left };
node.box_model().padding = { node_state.padding_top, node_state.padding_right, node_state.padding_bottom, node_state.padding_left };
node.box_model().border = { node_state.border_top, node_state.border_right, node_state.border_bottom, node_state.border_left };
node.box_model().margin = { node_state.margin_top, node_state.margin_right, node_state.margin_bottom, node_state.margin_left };
// For boxes, transfer relative offset and size.
if (is<Layout::Box>(node)) {
auto& box = static_cast<Layout::Box&>(node);
box.set_offset(node_state.offset);
box.set_content_size(node_state.content_width, node_state.content_height);
}
// For block containers, transfer line boxes.
if (is<Layout::BlockContainer>(node)) {
auto& block_container = static_cast<Layout::BlockContainer&>(node);
block_container.set_line_boxes(move(node_state.line_boxes));
}
}
}
Gfx::FloatRect margin_box_rect(Box const& box, FormattingState const& state)
{
auto const& box_state = state.get(box);
auto rect = Gfx::FloatRect { box_state.offset, { box_state.content_width, 0 } };
rect.set_x(rect.x() - box_state.margin_box_left());
rect.set_width(rect.width() + box_state.margin_box_left() + box_state.margin_box_right());
rect.set_y(rect.y() - box_state.margin_box_top());
rect.set_height(rect.height() + box_state.margin_box_top() + box_state.margin_box_bottom());
return rect;
}
Gfx::FloatRect margin_box_rect_in_ancestor_coordinate_space(Box const& box, Box const& ancestor_box, FormattingState const& state)
{
auto rect = margin_box_rect(box, state);
for (auto const* current = box.parent(); current; current = current->parent()) {
if (current == &ancestor_box)
break;
if (is<Box>(*current)) {
auto const& current_state = state.get(static_cast<Box const&>(*current));
rect.translate_by(current_state.offset);
}
}
return rect;
}
Gfx::FloatRect absolute_content_rect(Box const& box, FormattingState const& state)
{
auto const& box_state = state.get(box);
Gfx::FloatRect rect { box_state.offset, { box_state.content_width, box_state.content_height } };
for (auto* block = box.containing_block(); block; block = block->containing_block())
rect.translate_by(state.get(*block).offset);
return rect;
}
}