LibWeb: Move table grid slots functionality to separate module

Userland/Libraries/LibWeb/Layout/TableGrid.cpp

@@ -0,0 +1,95 @@
+/*
+ * Copyright (c) 2023, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/HTML/HTMLTableCellElement.h>
+#include <LibWeb/Layout/TableGrid.h>
+
+namespace Web::Layout {
+
+TableGrid TableGrid::calculate_row_column_grid(Box const& box, Vector<Cell>& cells, Vector<Row>& rows)
+{
+    // Implements https://html.spec.whatwg.org/multipage/tables.html#forming-a-table
+    TableGrid table_grid;
+
+    size_t x_width = 0, y_height = 0;
+    size_t x_current = 0, y_current = 0;
+    size_t max_cell_x = 0, max_cell_y = 0;
+
+    // Implements https://html.spec.whatwg.org/multipage/tables.html#algorithm-for-processing-rows
+    auto process_row = [&](auto& row) {
+        if (y_height == y_current)
+            y_height++;
+
+        x_current = 0;
+
+        for (auto* child = row.first_child(); child; child = child->next_sibling()) {
+            if (child->display().is_table_cell()) {
+                // Cells: While x_current is less than x_width and the slot with coordinate (x_current, y_current) already has a cell assigned to it, increase x_current by 1.
+                while (x_current < x_width && table_grid.m_occupancy_grid.contains(GridPosition { x_current, y_current }))
+                    x_current++;
+
+                Box const* box = static_cast<Box const*>(child);
+                if (x_current == x_width)
+                    x_width++;
+
+                size_t colspan = 1, rowspan = 1;
+                if (box->dom_node() && is<HTML::HTMLTableCellElement>(*box->dom_node())) {
+                    auto const& node = static_cast<HTML::HTMLTableCellElement const&>(*box->dom_node());
+                    colspan = node.col_span();
+                    rowspan = node.row_span();
+                }
+
+                if (x_width < x_current + colspan && y_current == 0)
+                    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++)
+                        table_grid.m_occupancy_grid.set(GridPosition { x, y }, true);
+                cells.append(Cell { *box, x_current, y_current, colspan, rowspan });
+                max_cell_x = max(x_current, max_cell_x);
+                max_cell_y = max(y_current, max_cell_y);
+
+                x_current += colspan;
+            }
+        }
+
+        rows.append(Row { row });
+        y_current++;
+    };
+
+    for_each_child_box_matching(box, is_table_row_group, [&](auto& row_group_box) {
+        for_each_child_box_matching(row_group_box, is_table_row, [&](auto& row_box) {
+            process_row(row_box);
+            return IterationDecision::Continue;
+        });
+    });
+
+    for_each_child_box_matching(box, is_table_row, [&](auto& row_box) {
+        process_row(row_box);
+        return IterationDecision::Continue;
+    });
+
+    table_grid.m_column_count = x_width;
+
+    for (auto& cell : cells) {
+        // Clip spans to the end of the table.
+        cell.row_span = min(cell.row_span, rows.size() - cell.row_index);
+        cell.column_span = min(cell.column_span, table_grid.m_column_count - cell.column_index);
+    }
+
+    return table_grid;
+}
+
+TableGrid TableGrid::calculate_row_column_grid(Box const& box)
+{
+    Vector<Cell> cells;
+    Vector<Row> rows;
+    return calculate_row_column_grid(box, cells, rows);
+}
+
+}