This closes #1047, stream writer support set panes (#1123)

- New exported error `ErrStreamSetPanes` has been added

5 files changed, 78 insertions, 42 deletions

diff --git a/errors.go b/errors.go
index 48476bc..fd896a6 100644
--- a/errors.go
+++ b/errors.go
@@ -91,6 +91,9 @@ var (
 	// ErrStreamSetColWidth defined the error message on set column width in
 	// stream writing mode.
 	ErrStreamSetColWidth = errors.New("must call the SetColWidth function before the SetRow function")
+	// ErrStreamSetPanes defined the error message on set panes in stream
+	// writing mode.
+	ErrStreamSetPanes = errors.New("must call the SetPanes function before the SetRow function")
 	// ErrColumnNumber defined the error message on receive an invalid column
 	// number.
 	ErrColumnNumber = fmt.Errorf(`the column number must be greater than or equal to %d and less than or equal to %d`, MinColumns, MaxColumns)
diff --git a/sheet.go b/sheet.go
index a737a9a..71123d7 100644
--- a/sheet.go
+++ b/sheet.go
@@ -683,8 +683,44 @@ func parsePanesOptions(opts string) (*panesOptions, error) {
 	return &format, err
 }
 
+// setPanes set create freeze panes and split panes by given options.
+func (ws *xlsxWorksheet) setPanes(panes string) error {
+	opts, err := parsePanesOptions(panes)
+	if err != nil {
+		return err
+	}
+	p := &xlsxPane{
+		ActivePane:  opts.ActivePane,
+		TopLeftCell: opts.TopLeftCell,
+		XSplit:      float64(opts.XSplit),
+		YSplit:      float64(opts.YSplit),
+	}
+	if opts.Freeze {
+		p.State = "frozen"
+	}
+	if ws.SheetViews == nil {
+		ws.SheetViews = &xlsxSheetViews{SheetView: []xlsxSheetView{{}}}
+	}
+	ws.SheetViews.SheetView[len(ws.SheetViews.SheetView)-1].Pane = p
+	if !(opts.Freeze) && !(opts.Split) {
+		if len(ws.SheetViews.SheetView) > 0 {
+			ws.SheetViews.SheetView[len(ws.SheetViews.SheetView)-1].Pane = nil
+		}
+	}
+	var s []*xlsxSelection
+	for _, p := range opts.Panes {
+		s = append(s, &xlsxSelection{
+			ActiveCell: p.ActiveCell,
+			Pane:       p.Pane,
+			SQRef:      p.SQRef,
+		})
+	}
+	ws.SheetViews.SheetView[len(ws.SheetViews.SheetView)-1].Selection = s
+	return err
+}
+
 // SetPanes provides a function to create and remove freeze panes and split panes
-// by given worksheet name and panes format set.
+// by given worksheet name and panes options.
 //
 // activePane defines the pane that is active. The possible values for this
 // attribute are defined in the following table:
@@ -768,39 +804,11 @@ func parsePanesOptions(opts string) (*panesOptions, error) {
 //
 //	f.SetPanes("Sheet1", `{"freeze":false,"split":false}`)
 func (f *File) SetPanes(sheet, panes string) error {
-	fs, _ := parsePanesOptions(panes)
 	ws, err := f.workSheetReader(sheet)
 	if err != nil {
 		return err
 	}
-	p := &xlsxPane{
-		ActivePane:  fs.ActivePane,
-		TopLeftCell: fs.TopLeftCell,
-		XSplit:      float64(fs.XSplit),
-		YSplit:      float64(fs.YSplit),
-	}
-	if fs.Freeze {
-		p.State = "frozen"
-	}
-	if ws.SheetViews == nil {
-		ws.SheetViews = &xlsxSheetViews{SheetView: []xlsxSheetView{{}}}
-	}
-	ws.SheetViews.SheetView[len(ws.SheetViews.SheetView)-1].Pane = p
-	if !(fs.Freeze) && !(fs.Split) {
-		if len(ws.SheetViews.SheetView) > 0 {
-			ws.SheetViews.SheetView[len(ws.SheetViews.SheetView)-1].Pane = nil
-		}
-	}
-	var s []*xlsxSelection
-	for _, p := range fs.Panes {
-		s = append(s, &xlsxSelection{
-			ActiveCell: p.ActiveCell,
-			Pane:       p.Pane,
-			SQRef:      p.SQRef,
-		})
-	}
-	ws.SheetViews.SheetView[len(ws.SheetViews.SheetView)-1].Selection = s
-	return err
+	return ws.setPanes(panes)
 }
 
 // GetSheetVisible provides a function to get worksheet visible by given worksheet
diff --git a/sheet_test.go b/sheet_test.go
index 74ca02c..6e87de9 100644
--- a/sheet_test.go
+++ b/sheet_test.go
@@ -34,7 +34,7 @@ func TestSetPane(t *testing.T) {
 	assert.NoError(t, f.SetPanes("Panes 3", `{"freeze":false,"split":true,"x_split":3270,"y_split":1800,"top_left_cell":"N57","active_pane":"bottomLeft","panes":[{"sqref":"I36","active_cell":"I36"},{"sqref":"G33","active_cell":"G33","pane":"topRight"},{"sqref":"J60","active_cell":"J60","pane":"bottomLeft"},{"sqref":"O60","active_cell":"O60","pane":"bottomRight"}]}`))
 	f.NewSheet("Panes 4")
 	assert.NoError(t, f.SetPanes("Panes 4", `{"freeze":true,"split":false,"x_split":0,"y_split":9,"top_left_cell":"A34","active_pane":"bottomLeft","panes":[{"sqref":"A11:XFD11","active_cell":"A11","pane":"bottomLeft"}]}`))
-	assert.NoError(t, f.SetPanes("Panes 4", ""))
+	assert.EqualError(t, f.SetPanes("Panes 4", ""), "unexpected end of JSON input")
 	assert.EqualError(t, f.SetPanes("SheetN", ""), "sheet SheetN does not exist")
 	assert.NoError(t, f.SaveAs(filepath.Join("test", "TestSetPane.xlsx")))
 	// Test add pane on empty sheet views worksheet
diff --git a/stream.go b/stream.go
index 66c0fda..9f47762 100644
--- a/stream.go
+++ b/stream.go
@@ -119,7 +119,7 @@ func (f *File) NewStreamWriter(sheet string) (*StreamWriter, error) {
 	f.streams[sheetXMLPath] = sw
 
 	_, _ = sw.rawData.WriteString(xml.Header + `<worksheet` + templateNamespaceIDMap)
-	bulkAppendFields(&sw.rawData, sw.worksheet, 2, 5)
+	bulkAppendFields(&sw.rawData, sw.worksheet, 2, 3)
 	return sw, err
 }
 
@@ -351,13 +351,7 @@ func (sw *StreamWriter) SetRow(cell string, values []interface{}, opts ...RowOpt
 	if err != nil {
 		return err
 	}
-	if !sw.sheetWritten {
-		if len(sw.cols) > 0 {
-			_, _ = sw.rawData.WriteString("<cols>" + sw.cols + "</cols>")
-		}
-		_, _ = sw.rawData.WriteString(`<sheetData>`)
-		sw.sheetWritten = true
-	}
+	sw.writeSheetData()
 	options := parseRowOpts(opts...)
 	attrs, err := options.marshalAttrs()
 	if err != nil {
@@ -415,6 +409,16 @@ func (sw *StreamWriter) SetColWidth(min, max int, width float64) error {
 	return nil
 }
 
+// SetPanes provides a function to create and remove freeze panes and split
+// panes by given worksheet name and panes options for the StreamWriter. Note
+// that you must call the 'SetPanes' function before the 'SetRow' function.
+func (sw *StreamWriter) SetPanes(panes string) error {
+	if sw.sheetWritten {
+		return ErrStreamSetPanes
+	}
+	return sw.worksheet.setPanes(panes)
+}
+
 // MergeCell provides a function to merge cells by a given range reference for
 // the StreamWriter. Don't create a merged cell that overlaps with another
 // existing merged cell.
@@ -507,6 +511,7 @@ func setCellIntFunc(c *xlsxC, val interface{}) (err error) {
 	return
 }
 
+// writeCell constructs a cell XML and writes it to the buffer.
 func writeCell(buf *bufferedWriter, c xlsxC) {
 	_, _ = buf.WriteString(`<c`)
 	if c.XMLSpace.Value != "" {
@@ -539,12 +544,22 @@ func writeCell(buf *bufferedWriter, c xlsxC) {
 	_, _ = buf.WriteString(`</c>`)
 }
 
-// Flush ending the streaming writing process.
-func (sw *StreamWriter) Flush() error {
+// writeSheetData prepares the element preceding sheetData and writes the
+// sheetData XML start element to the buffer.
+func (sw *StreamWriter) writeSheetData() {
 	if !sw.sheetWritten {
+		bulkAppendFields(&sw.rawData, sw.worksheet, 4, 5)
+		if len(sw.cols) > 0 {
+			_, _ = sw.rawData.WriteString("<cols>" + sw.cols + "</cols>")
+		}
 		_, _ = sw.rawData.WriteString(`<sheetData>`)
 		sw.sheetWritten = true
 	}
+}
+
+// Flush ending the streaming writing process.
+func (sw *StreamWriter) Flush() error {
+	sw.writeSheetData()
 	_, _ = sw.rawData.WriteString(`</sheetData>`)
 	bulkAppendFields(&sw.rawData, sw.worksheet, 8, 15)
 	mergeCells := strings.Builder{}
diff --git a/stream_test.go b/stream_test.go
index 3c2cc69..91aa580 100644
--- a/stream_test.go
+++ b/stream_test.go
@@ -146,7 +146,17 @@ func TestStreamSetColWidth(t *testing.T) {
 	assert.ErrorIs(t, streamWriter.SetColWidth(MaxColumns+1, 3, 20), ErrColumnNumber)
 	assert.EqualError(t, streamWriter.SetColWidth(1, 3, MaxColumnWidth+1), ErrColumnWidth.Error())
 	assert.NoError(t, streamWriter.SetRow("A1", []interface{}{"A", "B", "C"}))
-	assert.EqualError(t, streamWriter.SetColWidth(2, 3, 20), ErrStreamSetColWidth.Error())
+	assert.ErrorIs(t, streamWriter.SetColWidth(2, 3, 20), ErrStreamSetColWidth)
+}
+
+func TestStreamSetPanes(t *testing.T) {
+	file, paneOpts := NewFile(), `{"freeze":true,"split":false,"x_split":1,"y_split":0,"top_left_cell":"B1","active_pane":"topRight","panes":[{"sqref":"K16","active_cell":"K16","pane":"topRight"}]}`
+	streamWriter, err := file.NewStreamWriter("Sheet1")
+	assert.NoError(t, err)
+	assert.NoError(t, streamWriter.SetPanes(paneOpts))
+	assert.EqualError(t, streamWriter.SetPanes(""), "unexpected end of JSON input")
+	assert.NoError(t, streamWriter.SetRow("A1", []interface{}{"A", "B", "C"}))
+	assert.ErrorIs(t, streamWriter.SetPanes(paneOpts), ErrStreamSetPanes)
 }
 
 func TestStreamTable(t *testing.T) {