This closes #1290 and closes #1328

- Add new smooth field in chart format parameter, support specify if smooth line chart
- Fix decimal number format round issue with build-in number format

cell_test.go

@@ -699,6 +699,14 @@ func TestFormattedValue2(t *testing.T) {
 	})
 	v = f.formattedValue(1, "43528", false)
 	assert.Equal(t, "43528", v)
+
+	// formatted decimal value with build-in number format ID
+	styleID, err := f.NewStyle(&Style{
+		NumFmt: 1,
+	})
+	assert.NoError(t, err)
+	v = f.formattedValue(styleID, "310.56", false)
+	assert.Equal(t, "311", v)
 }
 
 func TestSharedStringsError(t *testing.T) {

drawing.go

@@ -543,9 +543,6 @@ func (f *File) drawLineChart(formatSet *formatChart) *cPlotArea {
 			},
 			Ser:   f.drawChartSeries(formatSet),
 			DLbls: f.drawChartDLbls(formatSet),
-			Smooth: &attrValBool{
-				Val: boolPtr(false),
-			},
 			AxID: []*attrValInt{
 				{Val: intPtr(754001152)},
 				{Val: intPtr(753999904)},
@@ -757,6 +754,7 @@ func (f *File) drawChartSeries(formatSet *formatChart) *[]cSer {
 			DLbls:            f.drawChartSeriesDLbls(formatSet),
 			InvertIfNegative: &attrValBool{Val: boolPtr(false)},
 			Cat:              f.drawChartSeriesCat(formatSet.Series[k], formatSet),
+			Smooth:           &attrValBool{Val: boolPtr(formatSet.Series[k].Line.Smooth)},
 			Val:              f.drawChartSeriesVal(formatSet.Series[k], formatSet),
 			XVal:             f.drawChartSeriesXVal(formatSet.Series[k], formatSet),
 			YVal:             f.drawChartSeriesYVal(formatSet.Series[k], formatSet),

styles.go

@@ -852,7 +852,7 @@ func formatToInt(v, format string, date1904 bool) string {
 	if err != nil {
 		return v
 	}
-	return fmt.Sprintf("%d", int64(f))
+	return fmt.Sprintf("%d", int64(math.Round(f)))
 }
 
 // formatToFloat provides a function to convert original string to float

xmlChart.go

@@ -620,9 +620,10 @@ type formatChartSeries struct {
 	Categories string `json:"categories"`
 	Values     string `json:"values"`
 	Line       struct {
-		None  bool    `json:"none"`
-		Color string  `json:"color"`
-		Width float64 `json:"width"`
+		None   bool    `json:"none"`
+		Color  string  `json:"color"`
+		Smooth bool    `json:"smooth"`
+		Width  float64 `json:"width"`
 	} `json:"line"`
 	Marker struct {
 		Symbol string  `json:"symbol"`