Supports streaming write.

[xiwh]

Description

When exporting a large dataset, the browser takes a while to show the download dialog.

Steps to reproduce the issue:

func Export(w http.ResponseWriter, req *http.Request) {
	w.Header().Set("Content-Type", "application/octet-stream")
	w.Header().Set("Content-Disposition", "attachment;filename=export.xlsx")
	w.Header().Set("Content-Transfer-Encoding", "binary")
	w.(http.Flusher).Flush()

	f := excelize.NewFile()
	defer func() {
		if err := f.Close(); err != nil {
			fmt.Println(err)
		}
	}()
	sw, err := f.NewStreamWriter("Sheet1")
	if err != nil {
		fmt.Println(err)
		return
	}
	styleID, err := f.NewStyle(&excelize.Style{Font: &excelize.Font{Color: "777777"}})
	if err != nil {
		fmt.Println(err)
		return
	}
	if err := sw.SetRow("A1",
		[]interface{}{
			excelize.Cell{StyleID: styleID, Value: "Data"},
			[]excelize.RichTextRun{
				{Text: "Rich ", Font: &excelize.Font{Color: "2354e8"}},
				{Text: "Text", Font: &excelize.Font{Color: "e83723"}},
			},
		},
		excelize.RowOpts{Height: 45, Hidden: false}); err != nil {
		fmt.Println(err)
		return
	}
	for rowID := 2; rowID <= 1000000; rowID++ {
		row := make([]interface{}, 50)
		for colID := 0; colID < 50; colID++ {
			row[colID] = rand.Intn(640000)
		}
		cell, err := excelize.CoordinatesToCellName(1, rowID)
		if err != nil {
			fmt.Println(err)
			break
		}
		if err := sw.SetRow(cell, row); err != nil {
			fmt.Println(err)
			break
		}
	}
	if err := sw.Flush(); err != nil {
		fmt.Println(err)
		return
	}
	_ = f.Write(w)
}

Describe the results you received:

Describe the results you expected:

Output of go version:

go version go1.19.2 windows/amd64

Excelize version or commit ID:

v2.7.1

Environment details (OS, Microsoft Excel™ version, physical, etc.):

[xuri]

Thanks for your issue. You already using the stream writer in your code. What's your received and whats the results you expected? Could you follow the issue template to provide more details about this?

[xiwh]

Thanks for your issue. You already using the stream writer in your code. What's your received and whats the results you expected? Could you follow the issue template to provide more details about this?

Thank you for your support. It appears I didn't explain it clearly. What I aim to achieve is to progressively write to http.ResponseWriter when calling sw.Flush(). Currently, when exporting large files, we have to wait for the entire write operation to finish, leading to a substantial delay before the browser displays the file download dialog

[xuri]

Thanks for your details. This is similar to issues #753 and #1052. The workbook serialization should be waiting for all worksheets has be ready. Maybe an asynchrony download design will be better for generating a large workbook.

[xiwh]

Thanks for your details. This is similar to issues #753 and #1052. The workbook serialization should be waiting for all worksheets has be ready. Maybe an asynchrony download design will be better for generating a large workbook.

Thank you for your response. I have found an alternative solution by triggering the download dialog through JavaScript using XMLHttpRequest.