spreadsheet: support rotated cells

Fixes unidoc#226

_examples/spreadsheet/rotated-cells/main.go

@@ -0,0 +1,31 @@
+// Copyright 2017 Baliance. All rights reserved.
+package main
+
+import (
+	"log"
+
+	"baliance.com/gooxml/spreadsheet"
+)
+
+var lorem = `Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin lobortis, lectus dictum feugiat tempus, sem neque finibus enim, sed eleifend sem nunc ac diam. Vestibulum tempus sagittis elementum`
+
+func main() {
+	ss := spreadsheet.New()
+	// add a single sheet
+	sheet := ss.AddSheet()
+
+	row := sheet.AddRow()
+	cell := row.AddCell()
+
+	rotated := ss.StyleSheet.AddCellStyle()
+	rotated.SetRotation(45)
+
+	cell.SetString(lorem)
+	cell.SetStyle(rotated)
+
+	if err := ss.Validate(); err != nil {
+		log.Fatalf("error validating sheet: %s", err)
+	}
+
+	ss.SaveToFile("rotated.xlsx")
+}

spreadsheet/cellstyle.go

@@ -88,6 +88,15 @@ func (cs CellStyle) SetHorizontalAlignment(a sml.ST_HorizontalAlignment) {
 	cs.xf.ApplyAlignmentAttr = gooxml.Bool(true)
 }
 
+// SetRotation configures the cell to be rotated.
+func (cs CellStyle) SetRotation(deg uint8) {
+	if cs.xf.Alignment == nil {
+		cs.xf.Alignment = sml.NewCT_CellAlignment()
+	}
+	cs.xf.ApplyAlignmentAttr = gooxml.Bool(true)
+	cs.xf.Alignment.TextRotationAttr = gooxml.Uint8(deg)
+}
+
 // SetVerticalAlignment sets the vertical alignment of a cell style.
 func (cs CellStyle) SetVerticalAlignment(a sml.ST_VerticalAlignment) {
 	if cs.xf.Alignment == nil {