ladybird/Userland/Libraries/LibWeb/Layout/TableFormattingContext.cpp
Aliaksandr Kalenik b2a04ff48a LibWeb: Consider percent and fixed widths in table column distribution
Change column distribution to take in account is_length() and
is_percentage() width values instead of treating all cells like
they have auto width by implementing it in the way described
in CSS Tables 3 spec:
https://www.w3.org/TR/css-tables-3/#width-distribution-algorithm

distribute_width_to_column() is structured to follow schema:
w3.org/TR/css-tables-3/images/CSS-Tables-Column-Width-Assignment.svg
2023-01-06 12:01:46 +01:00

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/*
* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibWeb/DOM/Node.h>
#include <LibWeb/HTML/BrowsingContext.h>
#include <LibWeb/Layout/Box.h>
#include <LibWeb/Layout/InlineFormattingContext.h>
#include <LibWeb/Layout/TableBox.h>
#include <LibWeb/Layout/TableCellBox.h>
#include <LibWeb/Layout/TableFormattingContext.h>
#include <LibWeb/Layout/TableRowBox.h>
#include <LibWeb/Layout/TableRowGroupBox.h>
struct GridPosition {
size_t x;
size_t y;
};
inline bool operator==(GridPosition const& a, GridPosition const& b)
{
return a.x == b.x && a.y == b.y;
}
namespace AK {
template<>
struct Traits<GridPosition> : public GenericTraits<GridPosition> {
static unsigned hash(GridPosition const& key)
{
return pair_int_hash(key.x, key.y);
}
};
}
namespace Web::Layout {
TableFormattingContext::TableFormattingContext(LayoutState& state, BlockContainer const& root, FormattingContext* parent)
: FormattingContext(Type::Table, state, root, parent)
{
}
TableFormattingContext::~TableFormattingContext() = default;
void TableFormattingContext::calculate_row_column_grid(Box const& box)
{
// Implements https://html.spec.whatwg.org/multipage/tables.html#forming-a-table
HashMap<GridPosition, bool> grid;
size_t x_width = 0, y_height = 0;
size_t x_current = 0, y_current = 0;
auto process_row = [&](auto& row) {
if (y_height == y_current)
y_height++;
x_current = 0;
while (x_current < x_width && grid.contains(GridPosition { x_current, y_current }))
x_current++;
for (auto* child = row.first_child(); child; child = child->next_sibling()) {
if (is<TableCellBox>(*child)) {
Box* box = static_cast<Box*>(child);
if (x_current == x_width)
x_width++;
const size_t colspan = static_cast<TableCellBox*>(child)->colspan();
const size_t rowspan = static_cast<TableCellBox*>(child)->rowspan();
if (x_width < x_current + colspan)
x_width = x_current + colspan;
if (y_height < y_current + rowspan)
y_height = y_current + rowspan;
for (size_t y = y_current; y < y_current + rowspan; y++)
for (size_t x = x_current; x < x_current + colspan; x++)
grid.set(GridPosition { x, y }, true);
m_cells.append(Cell { *box, x_current, y_current, colspan, rowspan });
x_current += colspan;
}
}
m_rows.append(Row { row });
y_current++;
};
box.template for_each_child_of_type<TableRowGroupBox>([&](auto& row_group_box) {
row_group_box.template for_each_child_of_type<TableRowBox>([&](auto& row) {
process_row(row);
return IterationDecision::Continue;
});
});
box.template for_each_child_of_type<TableRowBox>([&](auto& row) {
process_row(row);
return IterationDecision::Continue;
});
m_columns.resize(x_width);
}
void TableFormattingContext::compute_table_measures()
{
for (auto& cell : m_cells) {
auto width_of_containing_block = m_available_space->width.to_px();
auto width_of_containing_block_as_length = CSS::Length::make_px(width_of_containing_block);
auto& computed_values = cell.box.computed_values();
CSSPixels padding_left = computed_values.padding().left().resolved(cell.box, width_of_containing_block_as_length).to_px(cell.box);
CSSPixels padding_right = computed_values.padding().right().resolved(cell.box, width_of_containing_block_as_length).to_px(cell.box);
auto is_left_most_cell = cell.column_index == 0;
auto is_right_most_cell = cell.column_index == m_columns.size() - 1;
auto should_hide_borders = cell.box.computed_values().border_collapse() == CSS::BorderCollapse::Collapse;
CSSPixels border_left = should_hide_borders && !is_left_most_cell ? 0 : computed_values.border_left().width;
CSSPixels border_right = should_hide_borders && !is_right_most_cell ? 0 : computed_values.border_right().width;
CSSPixels width = computed_values.width().resolved(cell.box, width_of_containing_block_as_length).to_px(cell.box);
auto cell_intrinsic_offsets = padding_left + padding_right + border_left + border_right;
auto min_content_width = calculate_min_content_width(cell.box);
auto max_content_width = calculate_max_content_width(cell.box);
CSSPixels min_width = min_content_width;
if (!computed_values.min_width().is_auto())
min_width = max(min_width, computed_values.min_width().resolved(cell.box, width_of_containing_block_as_length).to_px(cell.box));
CSSPixels max_width = computed_values.width().is_auto() ? max_content_width.value() : width;
if (!computed_values.max_width().is_none())
max_width = min(max_width, computed_values.max_width().resolved(cell.box, width_of_containing_block_as_length).to_px(cell.box));
auto computed_width = computed_values.width();
if (computed_width.is_percentage()) {
m_columns[cell.column_index].type = ColumnType::Percent;
m_columns[cell.column_index].percentage_width = max(m_columns[cell.column_index].percentage_width, computed_width.percentage().value());
} else if (computed_width.is_length()) {
m_columns[cell.column_index].type = ColumnType::Pixel;
}
auto cell_outer_min_content_width = min_width + cell_intrinsic_offsets;
auto cell_outer_max_content_width = max(max(width, min_width), max_width) + cell_intrinsic_offsets;
m_columns[cell.column_index].min_width = max(m_columns[cell.column_index].min_width, cell_outer_min_content_width);
m_columns[cell.column_index].max_width = max(m_columns[cell.column_index].max_width, cell_outer_max_content_width);
}
}
void TableFormattingContext::compute_table_width()
{
auto const& table_box = context_box();
auto& table_box_state = m_state.get_mutable(table_box);
auto& computed_values = table_box.computed_values();
CSSPixels width_of_table_containing_block = m_state.get(*table_box.containing_block()).content_width();
// The row/column-grid width minimum (GRIDMIN) width is the sum of the min-content width
// of all the columns plus cell spacing or borders.
CSSPixels grid_min = 0.0f;
for (auto& column : m_columns) {
grid_min += column.min_width;
}
// The row/column-grid width maximum (GRIDMAX) width is the sum of the max-content width
// of all the columns plus cell spacing or borders.
CSSPixels grid_max = 0.0f;
for (auto& column : m_columns) {
grid_max += column.max_width;
}
// The used min-width of a table is the greater of the resolved min-width, CAPMIN, and GRIDMIN.
auto used_min_width = grid_min;
if (!computed_values.min_width().is_auto()) {
used_min_width = max(used_min_width, computed_values.min_width().resolved(table_box, CSS::Length::make_px(width_of_table_containing_block)).to_px(table_box));
}
CSSPixels used_width;
if (computed_values.width().is_auto()) {
// If the table-root has 'width: auto', the used width is the greater of
// min(GRIDMAX, the tables containing block width), the used min-width of the table.
used_width = max(min(grid_max, width_of_table_containing_block), used_min_width);
table_box_state.set_content_width(used_width);
} else {
// If the table-roots width property has a computed value (resolving to
// resolved-table-width) other than auto, the used width is the greater
// of resolved-table-width, and the used min-width of the table.
CSSPixels resolved_table_width = computed_values.width().resolved(table_box, CSS::Length::make_px(width_of_table_containing_block)).to_px(table_box);
used_width = max(resolved_table_width, used_min_width);
table_box_state.set_content_width(used_width);
}
}
void TableFormattingContext::distribute_width_to_columns()
{
// Implements https://www.w3.org/TR/css-tables-3/#width-distribution-algorithm
CSSPixels available_width = m_state.get(context_box()).content_width();
auto columns_total_used_width = [&]() {
CSSPixels total_used_width = 0;
for (auto& column : m_columns) {
total_used_width += column.used_width;
}
return total_used_width;
};
auto column_preferred_width = [&](Column& column) {
switch (column.type) {
case ColumnType::Percent: {
return max(column.min_width, column.percentage_width / 100 * available_width);
}
case ColumnType::Pixel:
case ColumnType::Auto: {
return column.max_width;
}
default: {
VERIFY_NOT_REACHED();
}
}
};
auto expand_columns_to_fill_available_width = [&](ColumnType column_type) {
CSSPixels remaining_available_width = available_width;
CSSPixels total_preferred_width_increment = 0;
for (auto& column : m_columns) {
remaining_available_width -= column.used_width;
if (column.type == column_type) {
total_preferred_width_increment += column_preferred_width(column) - column.min_width;
}
}
for (auto& column : m_columns) {
if (column.type == column_type) {
CSSPixels preferred_width_increment = column_preferred_width(column) - column.min_width;
column.used_width += preferred_width_increment * remaining_available_width / total_preferred_width_increment;
}
}
};
auto shrink_columns_to_fit_available_width = [&](ColumnType column_type) {
for (auto& column : m_columns) {
if (column.type == column_type)
column.used_width = column.min_width;
}
expand_columns_to_fill_available_width(column_type);
};
for (auto& column : m_columns) {
column.used_width = column.min_width;
}
for (auto& column : m_columns) {
if (column.type == ColumnType::Percent) {
column.used_width = max(column.min_width, column.percentage_width / 100 * available_width);
}
}
if (columns_total_used_width() > available_width) {
shrink_columns_to_fit_available_width(ColumnType::Percent);
return;
}
for (auto& column : m_columns) {
if (column.type == ColumnType::Pixel) {
column.used_width = column.max_width;
}
}
if (columns_total_used_width() > available_width) {
shrink_columns_to_fit_available_width(ColumnType::Pixel);
return;
}
if (columns_total_used_width() < available_width) {
expand_columns_to_fill_available_width(ColumnType::Auto);
}
if (columns_total_used_width() < available_width) {
expand_columns_to_fill_available_width(ColumnType::Pixel);
}
if (columns_total_used_width() < available_width) {
expand_columns_to_fill_available_width(ColumnType::Percent);
}
}
void TableFormattingContext::determine_intrisic_size_of_table_container(AvailableSpace const& available_space)
{
auto const& table_box = context_box();
auto& table_box_state = m_state.get_mutable(table_box);
if (available_space.width.is_min_content()) {
// The min-content width of a table is the width required to fit all of its columns min-content widths and its undistributable spaces.
CSSPixels grid_min = 0.0f;
for (auto& column : m_columns)
grid_min += column.min_width;
table_box_state.set_content_width(grid_min);
}
if (available_space.width.is_max_content()) {
// The max-content width of a table is the width required to fit all of its columns max-content widths and its undistributable spaces.
CSSPixels grid_max = 0.0f;
for (auto& column : m_columns)
grid_max += column.max_width;
table_box_state.set_content_width(grid_max);
}
}
void TableFormattingContext::run(Box const& box, LayoutMode, AvailableSpace const& available_space)
{
m_available_space = available_space;
CSSPixels total_content_height = 0;
// Determine the number of rows/columns the table requires.
calculate_row_column_grid(box);
// Compute the minimum width of each column.
compute_table_measures();
if (available_space.width.is_intrinsic_sizing_constraint()) {
determine_intrisic_size_of_table_container(available_space);
return;
}
// Compute the width of the table.
compute_table_width();
// Distribute the width of the table among columns.
distribute_width_to_columns();
CSSPixels left_column_offset = 0;
for (auto& column : m_columns) {
column.left_offset = left_column_offset;
left_column_offset += column.used_width;
}
for (auto& cell : m_cells) {
auto& cell_state = m_state.get_mutable(cell.box);
CSSPixels span_width = 0;
for (size_t i = 0; i < cell.column_span; ++i)
span_width += m_columns[cell.column_index + i].used_width;
auto width_of_containing_block = m_state.get(*cell.box.containing_block()).content_width();
auto width_of_containing_block_as_length = CSS::Length::make_px(width_of_containing_block);
cell_state.padding_top = cell.box.computed_values().padding().top().resolved(cell.box, width_of_containing_block_as_length).to_px(cell.box);
cell_state.padding_bottom = cell.box.computed_values().padding().bottom().resolved(cell.box, width_of_containing_block_as_length).to_px(cell.box);
cell_state.padding_left = cell.box.computed_values().padding().left().resolved(cell.box, width_of_containing_block_as_length).to_px(cell.box);
cell_state.padding_right = cell.box.computed_values().padding().right().resolved(cell.box, width_of_containing_block_as_length).to_px(cell.box);
auto is_top_most_cell = cell.row_index == 0;
auto is_left_most_cell = cell.column_index == 0;
auto is_right_most_cell = cell.column_index == m_columns.size() - 1;
auto is_bottom_most_cell = cell.row_index == m_rows.size() - 1;
auto should_hide_borders = cell.box.computed_values().border_collapse() == CSS::BorderCollapse::Collapse;
cell_state.border_top = (should_hide_borders && is_top_most_cell) ? 0 : cell.box.computed_values().border_top().width;
cell_state.border_bottom = (should_hide_borders && is_bottom_most_cell) ? 0 : cell.box.computed_values().border_bottom().width;
cell_state.border_left = (should_hide_borders && is_left_most_cell) ? 0 : cell.box.computed_values().border_left().width;
cell_state.border_right = (should_hide_borders && is_right_most_cell) ? 0 : cell.box.computed_values().border_right().width;
cell_state.set_content_width((span_width - cell_state.border_box_left() - cell_state.border_box_right()));
auto independent_formatting_context = layout_inside(cell.box, LayoutMode::Normal, cell_state.available_inner_space_or_constraints_from(available_space));
VERIFY(independent_formatting_context);
cell_state.set_content_height(independent_formatting_context->automatic_content_height());
independent_formatting_context->parent_context_did_dimension_child_root_box();
cell.baseline = box_baseline(m_state, cell.box);
auto& row = m_rows[cell.row_index];
row.used_width = max(row.used_width, cell_state.border_box_height());
row.baseline = max(row.baseline, cell.baseline);
}
CSSPixels row_top_offset = 0.0f;
for (size_t y = 0; y < m_rows.size(); y++) {
auto& row = m_rows[y];
auto& row_state = m_state.get_mutable(row.box);
CSSPixels row_width = 0.0f;
for (auto& column : m_columns) {
row_width += column.used_width;
}
row_state.set_content_height(row.used_width);
row_state.set_content_width(row_width);
row_state.set_content_y(row_top_offset);
row_top_offset += row_state.content_height();
}
CSSPixels row_group_top_offset = 0.0f;
box.for_each_child_of_type<TableRowGroupBox>([&](auto& row_group_box) {
CSSPixels row_group_height = 0.0f;
CSSPixels row_group_width = 0.0f;
auto& row_group_box_state = m_state.get_mutable(row_group_box);
row_group_box_state.set_content_y(row_group_top_offset);
CSSPixels row_top_offset = 0.0f;
row_group_box.template for_each_child_of_type<TableRowBox>([&](auto& row) {
auto& row_state = m_state.get_mutable(row);
row_state.set_content_y(row_top_offset);
row_group_height += row_state.border_box_height();
row_group_width = max(row_group_width, row_state.border_box_width());
row_top_offset += row_state.border_box_height();
});
row_group_top_offset += row_top_offset;
row_group_box_state.set_content_height(row_group_height);
row_group_box_state.set_content_width(row_group_width);
});
for (auto& cell : m_cells) {
auto& cell_state = m_state.get_mutable(cell.box);
auto& row_state = m_state.get(m_rows[cell.row_index].box);
CSSPixels const cell_border_box_height = cell_state.content_height() + cell_state.border_box_top() + cell_state.border_box_bottom();
CSSPixels const row_content_height = row_state.content_height();
auto const& vertical_align = cell.box.computed_values().vertical_align();
if (vertical_align.has<CSS::VerticalAlign>()) {
switch (vertical_align.get<CSS::VerticalAlign>()) {
case CSS::VerticalAlign::Middle: {
cell_state.padding_top += (row_content_height - cell_border_box_height) / 2;
cell_state.padding_bottom += (row_content_height - cell_border_box_height) / 2;
break;
}
// FIXME: implement actual 'top' and 'bottom' support instead of fall back to 'baseline'
case CSS::VerticalAlign::Top:
case CSS::VerticalAlign::Bottom:
case CSS::VerticalAlign::Baseline: {
cell_state.padding_top += m_rows[cell.row_index].baseline - cell.baseline;
cell_state.padding_bottom += row_content_height - cell_border_box_height;
break;
}
default:
VERIFY_NOT_REACHED();
}
}
cell_state.offset = row_state.offset.translated(cell_state.border_box_left() + m_columns[cell.column_index].left_offset, cell_state.border_box_top());
}
m_state.get_mutable(context_box()).set_content_height(total_content_height);
// FIXME: This is a total hack, we should respect the 'height' property.
m_automatic_content_height = total_content_height;
}
CSSPixels TableFormattingContext::automatic_content_height() const
{
return m_automatic_content_height;
}
}