Implement AddSubtable method for the Table component (#400)

* Implement AddSubtable method for the table component with test case.

pdf/creator/table.go

@@ -7,6 +7,7 @@ package creator
 
 import (
 	"errors"
+	"sort"
 
 	"github.com/unidoc/unidoc/common"
 	"github.com/unidoc/unidoc/pdf/contentstream/draw"
@@ -64,12 +65,7 @@ func newTable(cols int) *Table {
 		cells:            []*TableCell{},
 	}
 
-	// Initialize column widths as all equal.
-	colWidth := float64(1.0) / float64(cols)
-	for i := 0; i < cols; i++ {
-		t.colWidths = append(t.colWidths, colWidth)
-	}
-
+	t.resetColumnWidths()
 	return t
 }
 
@@ -86,6 +82,16 @@ func (table *Table) SetColumnWidths(widths ...float64) error {
 	return nil
 }
 
+func (table *Table) resetColumnWidths() {
+	table.colWidths = []float64{}
+	colWidth := float64(1.0) / float64(table.cols)
+
+	// Initialize column widths as all equal.
+	for i := 0; i < table.cols; i++ {
+		table.colWidths = append(table.colWidths, colWidth)
+	}
+}
+
 // Height returns the total height of all rows.
 func (table *Table) Height() float64 {
 	sum := float64(0.0)
@@ -166,6 +172,53 @@ func (table *Table) SetHeaderRows(startRow, endRow int) error {
 	return nil
 }
 
+// AddSubtable copies the cells of the subtable in the table, starting with the
+// specified position. The table row and column indices are 1-based, which
+// makes the position of the first cell of the first row of the table 1,1.
+// The table is automatically extended if the subtable exceeds its columns.
+// This can happen when the subtable has more columns than the table or when
+// one or more columns of the subtable starting from the specified position
+// exceed the last column of the table.
+func (table *Table) AddSubtable(row, col int, subtable *Table) {
+	for _, cell := range subtable.cells {
+		c := &TableCell{}
+		*c = *cell
+		c.table = table
+
+		// Adjust added cell column. Add extra columns to the table to
+		// accomodate the new cell, if needed.
+		c.col += col - 1
+		if colsLeft := table.cols - (c.col - 1); colsLeft < c.colspan {
+			table.cols += c.colspan - colsLeft
+			table.resetColumnWidths()
+			common.Log.Debug("Table: subtable exceeds destination table. Expanding table to %d columns.", table.cols)
+		}
+
+		// Extend number of rows, if needed.
+		c.row += row - 1
+		for c.row > table.rows {
+			table.rows++
+			table.rowHeights = append(table.rowHeights, table.defaultRowHeight)
+		}
+
+		table.cells = append(table.cells, c)
+	}
+
+	// Sort cells by row, column.
+	sort.Slice(table.cells, func(i, j int) bool {
+		rowA := table.cells[i].row
+		rowB := table.cells[j].row
+		if rowA < rowB {
+			return true
+		}
+		if rowA > rowB {
+			return false
+		}
+
+		return table.cells[i].col < table.cells[j].col
+	})
+}
+
 // GeneratePageBlocks generate the page blocks.  Multiple blocks are generated if the contents wrap
 // over multiple pages.
 // Implements the Drawable interface.

pdf/creator/table_test.go

@@ -406,3 +406,94 @@ func TestTableHeaderTest(t *testing.T) {
 		t.Fatalf("Fail: %v\n", err)
 	}
 }
+
+func TestTableSubtables(t *testing.T) {
+	c := New()
+	headerColor := ColorRGBFrom8bit(255, 255, 0)
+	footerColor := ColorRGBFrom8bit(0, 255, 0)
+
+	generateSubtable := func(rows, cols, index int, rightBorder bool) *Table {
+		subtable := c.NewTable(cols)
+
+		// Add header row.
+		sp := c.NewStyledParagraph()
+		sp.Append(fmt.Sprintf("Header of subtable %d", index))
+
+		cell := subtable.MultiColCell(cols)
+		cell.SetContent(sp)
+		cell.SetBorder(CellBorderSideAll, CellBorderStyleSingle, 1)
+		cell.SetHorizontalAlignment(CellHorizontalAlignmentCenter)
+		cell.SetBackgroundColor(headerColor)
+
+		for i := 0; i < rows; i++ {
+			for j := 0; j < cols; j++ {
+				sp = c.NewStyledParagraph()
+				sp.Append(fmt.Sprintf("%d-%d", i+1, j+1))
+				cell = subtable.NewCell()
+				cell.SetContent(sp)
+
+				if j == 0 {
+					cell.SetBorder(CellBorderSideLeft, CellBorderStyleSingle, 1)
+				}
+				if rightBorder && j == cols-1 {
+					cell.SetBorder(CellBorderSideRight, CellBorderStyleSingle, 1)
+				}
+			}
+		}
+
+		// Add footer row.
+		sp = c.NewStyledParagraph()
+		sp.Append(fmt.Sprintf("Footer of subtable %d", index))
+
+		cell = subtable.MultiColCell(cols)
+		cell.SetContent(sp)
+		cell.SetBorder(CellBorderSideAll, CellBorderStyleSingle, 1)
+		cell.SetHorizontalAlignment(CellHorizontalAlignmentCenter)
+		cell.SetBackgroundColor(footerColor)
+
+		return subtable
+	}
+
+	table := c.NewTable(6)
+
+	// Add subtable 1 on row 1, col 1 (4x4)
+	table.AddSubtable(1, 1, generateSubtable(4, 4, 1, false))
+
+	// Add subtable 2 on row 1, col 5 (4x4)
+	// Table will be expanded to 8 columns because the subtable does not fit.
+	table.AddSubtable(1, 5, generateSubtable(4, 4, 2, true))
+
+	// Add subtable 3 on row 7, col 1 (4x4)
+	table.AddSubtable(7, 1, generateSubtable(4, 4, 3, false))
+
+	// Add subtable 4 on row 7, col 5 (4x4)
+	table.AddSubtable(7, 5, generateSubtable(4, 4, 4, true))
+
+	// Add subtable 5 on row 13, col 3 (4x4)
+	table.AddSubtable(13, 3, generateSubtable(4, 4, 5, true))
+
+	// Add subtable 6 on row 13, col 1 (3x2)
+	table.AddSubtable(13, 1, generateSubtable(3, 2, 6, false))
+
+	// Add subtable 7 on row 13, col 7 (3x2)
+	table.AddSubtable(13, 7, generateSubtable(3, 2, 7, true))
+
+	// Add subtable 8 on row 18, col 1 (3x2)
+	table.AddSubtable(18, 1, generateSubtable(3, 2, 8, false))
+
+	// Add subtable 9 on row 19, col 3 (2x4)
+	table.AddSubtable(19, 3, generateSubtable(2, 4, 9, true))
+
+	// Add subtable 10 on row 18, col 7 (3x2)
+	table.AddSubtable(18, 7, generateSubtable(3, 2, 10, true))
+
+	err := c.Draw(table)
+	if err != nil {
+		t.Fatalf("Error drawing: %v", err)
+	}
+
+	err = c.WriteToFile(tempFile("table_add_subtables.pdf"))
+	if err != nil {
+		t.Fatalf("Fail: %v\n", err)
+	}
+}