- Conditional format with formula support, relate issue #75;

- go test and readme update

1 files changed, 14 insertions, 2 deletions

diff --git a/styles.go b/styles.go
index a055782..225cfe5 100644
--- a/styles.go
+++ b/styles.go
@@ -793,7 +793,7 @@ var validType = map[string]string{
 	"2_color_scale": "2_color_scale",
 	"3_color_scale": "3_color_scale",
 	"data_bar":      "dataBar",
-	"formula":       "expression", // Doesn't support currently
+	"formula":       "expression",
 }
 
 // criteriaType defined the list of valid criteria types.
@@ -2540,6 +2540,7 @@ func (f *File) SetConditionalFormat(sheet, area, formatSet string) {
 		"2_color_scale":   drawCondFmtColorScale,
 		"3_color_scale":   drawCondFmtColorScale,
 		"dataBar":         drawCondFmtDataBar,
+		"expression":      drawConfFmtExp,
 	}
 
 	xlsx := f.workSheetReader(sheet)
@@ -2554,7 +2555,7 @@ func (f *File) SetConditionalFormat(sheet, area, formatSet string) {
 		}
 		// Check for valid criteria types.
 		ct, ok = criteriaType[v.Criteria]
-		if !ok {
+		if !ok && vt != "expression" {
 			continue
 		}
 
@@ -2672,6 +2673,17 @@ func drawCondFmtDataBar(p int, ct string, format *formatConditional) *xlsxCfRule
 	}
 }
 
+// drawConfFmtExp provides function to create conditional formatting rule for
+// expression by given priority, criteria type and format settings.
+func drawConfFmtExp(p int, ct string, format *formatConditional) *xlsxCfRule {
+	return &xlsxCfRule{
+		Priority: p + 1,
+		Type:     validType[format.Type],
+		Formula:  []string{format.Criteria},
+		DxfID:    &format.Format,
+	}
+}
+
 // getPaletteColor provides function to convert the RBG color by given string.
 func getPaletteColor(color string) string {
 	return "FF" + strings.Replace(strings.ToUpper(color), "#", "", -1)