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LibWeb: Calculate valid grid areas

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When starting the GridFormattingContext, calculate the valid grid areas
as declared in the `grid-template-areas` property. Since this doesn't
change, are able to do this once and store the results.
This commit is contained in:
martinfalisse 2023-01-17 13:50:41 +01:00 • committed by Andreas Kling
parent fa5d016176
commit 47c77858b6
2 changed files with 60 additions and 0 deletions
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49
Userland/Libraries/LibWeb/Layout/GridFormattingContext.cpp
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@ -1591,6 +1591,53 @@ void GridFormattingContext::calculate_sizes_of_rows(Box const& box)
}
}
void GridFormattingContext::build_valid_grid_areas(Box const& box)
{
Vector<GridArea> found_grid_areas;
auto get_index_of_found_grid_area = [&](String needle) -> int {
for (size_t x = 0; x < found_grid_areas.size(); x++) {
if (found_grid_areas[x].name == needle)
return static_cast<int>(x);
}
return -1;
};
// https://www.w3.org/TR/css-grid-2/#grid-template-areas-property
// If a named grid area spans multiple grid cells, but those cells do not form a single
// filled-in rectangle, the declaration is invalid.
for (int y = 0; y < static_cast<int>(box.computed_values().grid_template_areas().size()); y++) {
for (int x = 0; x < static_cast<int>(box.computed_values().grid_template_areas()[y].size()); x++) {
auto grid_area_idx = get_index_of_found_grid_area(box.computed_values().grid_template_areas()[y][x]);
if (grid_area_idx == -1) {
found_grid_areas.append({ box.computed_values().grid_template_areas()[y][x], y, y + 1, x, x + 1 });
} else {
auto& grid_area = found_grid_areas[grid_area_idx];
if (grid_area.row_start == y) {
if (grid_area.column_end == x)
grid_area.column_end = grid_area.column_end + 1;
else
return;
} else {
if (grid_area.row_end == y) {
if (grid_area.column_start != x)
return;
grid_area.row_end = grid_area.row_end + 1;
} else if (grid_area.row_end == y + 1) {
if (grid_area.column_end < x || grid_area.column_end > x + 1)
return;
} else {
return;
}
}
}
}
}
for (auto const& checked_grid_area : found_grid_areas)
m_valid_grid_areas.append(checked_grid_area);
}
void GridFormattingContext::run(Box const& box, LayoutMode, AvailableSpace const& available_space)
{
auto grid_template_columns = box.computed_values().grid_template_columns();
@ -1614,6 +1661,8 @@ void GridFormattingContext::run(Box const& box, LayoutMode, AvailableSpace const
m_occupation_grid = OccupationGrid(column_count, row_count);
build_valid_grid_areas(box);
// https://drafts.csswg.org/css-grid/#auto-placement-algo
// 8.5. Grid Item Placement Algorithm