Create autowidth function to use on column

sheet.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"strconv"
+	"strings"
 
 	"github.com/shabbyrobe/xmlwriter"
 )
@@ -390,6 +391,39 @@ func (s *Sheet) SetColWidth(min, max int, width float64) {
 	})
 }
 
+// This can be use as the default scale function for the autowidth.
+// It works well with the default font sizes.
+func DefaultAutoWidth(s string) float64 {
+	return (float64(strings.Count(s, "")) + 3.0 ) * 1.2
+}
+
+// Tries to guess the best width for a column, based on the largest
+// cell content. A scale function needs to be provided.
+func (s *Sheet) SetColAutoWidth(colIndex int, width func (string) float64) error {
+	largestWidth := 0.0
+	rowVisitor := func (r *Row) error {
+		cell := r.GetCell(colIndex)
+		value, err := cell.FormattedValue()
+		if err != nil {
+			return err
+		}
+
+		if width(value) > largestWidth {
+			largestWidth = width(value)
+		}
+		return nil
+	}
+	err := s.ForEachRow(rowVisitor)
+
+	if err != nil {
+		return err
+	}
+
+	s.SetColWidth(colIndex, colIndex, largestWidth)
+
+	return nil
+}
+
 // Set the outline level for a range of columns.
 func (s *Sheet) SetOutlineLevel(minCol, maxCol int, outlineLevel uint8) {
 	s.setCol(minCol, maxCol, func(col *Col) {

sheet_test.go

@@ -615,6 +615,33 @@ func TestMakeXLSXSheet(t *testing.T) {
 		c.Assert(sheet.Cols.FindColByIndex(2).Min, qt.Equals, 2)
 	})
 
+
+	csRunO(c, "SetColAutoWidth", func(c *qt.C, option FileOption) {
+		file := NewFile(option)
+		sheet, _ := file.AddSheet("Sheet1")
+		row := sheet.AddRow()
+		cell11 := row.AddCell()
+		cell11.Value = "test 1"
+		cell12 := row.AddCell()
+		cell12.Value = "something else"
+
+		sheet.SetColAutoWidth(0, DefaultAutoWidth)
+
+		scaleFunc := func (s string) float64 {
+			return float64(strings.Count(s, "")) * 1.5
+		}
+		sheet.SetColAutoWidth(1, scaleFunc)
+
+		c.Assert(*sheet.Cols.FindColByIndex(0).Width, qt.Equals, 12.0)
+		c.Assert(sheet.Cols.FindColByIndex(0).Max, qt.Equals, 0)
+		c.Assert(sheet.Cols.FindColByIndex(0).Min, qt.Equals, 0)
+
+		c.Assert(*sheet.Cols.FindColByIndex(1).Width, qt.Equals, 22.5)
+		c.Assert(sheet.Cols.FindColByIndex(1).Max, qt.Equals, 1)
+		c.Assert(sheet.Cols.FindColByIndex(1).Min, qt.Equals, 1)
+	})
+
+
 	csRunO(c, "SetDataValidation", func(c *qt.C, option FileOption) {
 		file := NewFile(option)
 		sheet, _ := file.AddSheet("Sheet1")