From 8cb36ea74314a8425cc17be053543490719ce9eb Mon Sep 17 00:00:00 2001
From: Oliver <480930+rivo@users.noreply.github.com>
Date: Mon, 5 Mar 2018 14:07:18 +0100
Subject: [PATCH] Added expansion factor to table cells which grows columns if
 there is more space than needed. Resolves #62

---
 demos/presentation/table.go | 14 +++++-----
 table.go                    | 54 +++++++++++++++++++++++++++++++++++--
 2 files changed, 60 insertions(+), 8 deletions(-)

diff --git a/demos/presentation/table.go b/demos/presentation/table.go
index 77b5b5d..435e2d1 100644
--- a/demos/presentation/table.go
+++ b/demos/presentation/table.go
@@ -265,12 +265,14 @@ func Table(nextSlide func()) (title string, content tview.Primitive) {
 			} else if column == 0 || column >= 4 {
 				align = tview.AlignRight
 			}
-			table.SetCell(row, column, &tview.TableCell{
-				Text:          cell,
-				Color:         color,
-				Align:         align,
-				NotSelectable: row == 0 || column == 0,
-			})
+			tableCell := tview.NewTableCell(cell).
+				SetTextColor(color).
+				SetAlign(align).
+				SetSelectable(row != 0 && column != 0)
+			if column >= 1 && column <= 3 {
+				tableCell.SetExpansion(1)
+			}
+			table.SetCell(row, column, tableCell)
 		}
 	}
 	table.SetBorder(true).SetTitle("Table")
diff --git a/table.go b/table.go
index c7231e5..887d888 100644
--- a/table.go
+++ b/table.go
@@ -23,6 +23,10 @@ type TableCell struct {
 	// is cut off. Set to 0 if there is no maximum width.
 	MaxWidth int
 
+	// If the total table width is less than the available width, this value is
+	// used to add extra width to a column. See SetExpansion() for details.
+	Expansion int
+
 	// The color of the cell text.
 	Color tcell.Color
 
@@ -69,6 +73,27 @@ func (c *TableCell) SetMaxWidth(maxWidth int) *TableCell {
 	return c
 }
 
+// SetExpansion sets the value by which the column of this cell expands if the
+// available width for the table is more than the table width (prior to applying
+// this expansion value). This is a proportional value. The amount of unused
+// horizontal space is divided into widths to be added to each column. How much
+// extra width a column receives depends on the expansion value: A value of 0
+// (the default) will not cause the column to increase in width. Other values
+// are proportional, e.g. a value of 2 will cause a column to grow by twice
+// the amount of a column with a value of 1.
+//
+// Since this value affects an entire column, the maximum over all visible cells
+// in that column is used.
+//
+// This function panics if a negative value is provided.
+func (c *TableCell) SetExpansion(expansion int) *TableCell {
+	if expansion < 0 {
+		panic("Table cell expansion values may not be negative")
+	}
+	c.Expansion = expansion
+	return c
+}
+
 // SetTextColor sets the cell's text color.
 func (c *TableCell) SetTextColor(color tcell.Color) *TableCell {
 	c.Color = color
@@ -525,7 +550,10 @@ func (t *Table) Draw(screen tcell.Screen) {
 			break
 		}
 	}
-	var skipped, lastTableWidth int
+	var (
+		skipped, lastTableWidth, expansionTotal int
+		expansions                              []int
+	)
 ColumnLoop:
 	for column := 0; ; column++ {
 		// If we've moved beyond the right border, we stop or skip a column.
@@ -556,8 +584,9 @@ ColumnLoop:
 			widths = append(widths[:t.fixedColumns], widths[t.fixedColumns+1:]...)
 		}
 
-		// What's this column's width?
+		// What's this column's width (without expansion)?
 		maxWidth := -1
+		expansion := 0
 		for _, row := range rows {
 			if cell := getCell(row, column); cell != nil {
 				cellWidth := StringWidth(cell.Text)
@@ -567,6 +596,9 @@ ColumnLoop:
 				if cellWidth > maxWidth {
 					maxWidth = cellWidth
 				}
+				if cell.Expansion > expansion {
+					expansion = cell.Expansion
+				}
 			}
 		}
 		if maxWidth < 0 {
@@ -578,9 +610,27 @@ ColumnLoop:
 		widths = append(widths, maxWidth)
 		lastTableWidth = tableWidth
 		tableWidth += maxWidth + 1
+		expansions = append(expansions, expansion)
+		expansionTotal += expansion
 	}
 	t.columnOffset = skipped
 
+	// If we have space left, distribute it.
+	if tableWidth < width {
+		toDistribute := width - tableWidth
+		for index := range widths {
+			if expansionTotal <= 0 {
+				break
+			}
+			expansion := expansions[index]
+			expWidth := toDistribute * expansion / expansionTotal
+			widths[index] += expWidth
+			tableWidth += expWidth
+			toDistribute -= expWidth
+			expansionTotal -= expansion
+		}
+	}
+
 	// Helper function which draws border runes.
 	borderStyle := tcell.StyleDefault.Background(t.backgroundColor).Foreground(t.bordersColor)
 	drawBorder := func(colX, rowY int, ch rune) {