This closes #1219, fixes cell value reading issue, improves performance, and 1904 date system support

- Fix incorrect cell data types casting results when number formatting
- Support set cell value on 1904 date system enabled, ref #1212
- Improve performance for set sheet row and the merging cells, fix performance impact when resolving #1129

8 files changed, 63 insertions, 40 deletions

diff --git a/cell.go b/cell.go
index 70832ce..80c03ef 100644
--- a/cell.go
+++ b/cell.go
@@ -211,9 +211,12 @@ func (f *File) setCellTimeFunc(sheet, axis string, value time.Time) error {
 	ws.Lock()
 	cellData.S = f.prepareCellStyle(ws, col, row, cellData.S)
 	ws.Unlock()
-
+	date1904, wb := false, f.workbookReader()
+	if wb != nil && wb.WorkbookPr != nil {
+		date1904 = wb.WorkbookPr.Date1904
+	}
 	var isNum bool
-	cellData.T, cellData.V, isNum, err = setCellTime(value)
+	cellData.T, cellData.V, isNum, err = setCellTime(value, date1904)
 	if err != nil {
 		return err
 	}
@@ -225,11 +228,11 @@ func (f *File) setCellTimeFunc(sheet, axis string, value time.Time) error {
 
 // setCellTime prepares cell type and Excel time by given Go time.Time type
 // timestamp.
-func setCellTime(value time.Time) (t string, b string, isNum bool, err error) {
+func setCellTime(value time.Time, date1904 bool) (t string, b string, isNum bool, err error) {
 	var excelTime float64
 	_, offset := value.In(value.Location()).Zone()
 	value = value.Add(time.Duration(offset) * time.Second)
-	if excelTime, err = timeToExcelTime(value); err != nil {
+	if excelTime, err = timeToExcelTime(value, date1904); err != nil {
 		return
 	}
 	isNum = excelTime > 0
@@ -1122,8 +1125,7 @@ func (f *File) formattedValue(s int, v string, raw bool) string {
 	if wb != nil && wb.WorkbookPr != nil {
 		date1904 = wb.WorkbookPr.Date1904
 	}
-	ok := builtInNumFmtFunc[numFmtID]
-	if ok != nil {
+	if ok := builtInNumFmtFunc[numFmtID]; ok != nil {
 		return ok(v, builtInNumFmt[numFmtID], date1904)
 	}
 	if styleSheet == nil || styleSheet.NumFmts == nil {
@@ -1140,15 +1142,18 @@ func (f *File) formattedValue(s int, v string, raw bool) string {
 // prepareCellStyle provides a function to prepare style index of cell in
 // worksheet by given column index and style index.
 func (f *File) prepareCellStyle(ws *xlsxWorksheet, col, row, style int) int {
-	if ws.Cols != nil && style == 0 {
+	if style != 0 {
+		return style
+	}
+	if ws.Cols != nil {
 		for _, c := range ws.Cols.Col {
 			if c.Min <= col && col <= c.Max && c.Style != 0 {
 				return c.Style
 			}
 		}
 	}
-	for rowIdx := range ws.SheetData.Row {
-		if styleID := ws.SheetData.Row[rowIdx].S; style == 0 && styleID != 0 {
+	if row <= len(ws.SheetData.Row) {
+		if styleID := ws.SheetData.Row[row-1].S; styleID != 0 {
 			return styleID
 		}
 	}
diff --git a/cell_test.go b/cell_test.go
index 77179cc..8ed8e1f 100644
--- a/cell_test.go
+++ b/cell_test.go
@@ -192,7 +192,7 @@ func TestSetCellTime(t *testing.T) {
 	} {
 		timezone, err := time.LoadLocation(location)
 		assert.NoError(t, err)
-		_, b, isNum, err := setCellTime(date.In(timezone))
+		_, b, isNum, err := setCellTime(date.In(timezone), false)
 		assert.NoError(t, err)
 		assert.Equal(t, true, isNum)
 		assert.Equal(t, expected, b)
diff --git a/date.go b/date.go
index 1574af7..3e81319 100644
--- a/date.go
+++ b/date.go
@@ -32,21 +32,19 @@ var (
 )
 
 // timeToExcelTime provides a function to convert time to Excel time.
-func timeToExcelTime(t time.Time) (float64, error) {
-	// TODO in future this should probably also handle date1904 and like TimeFromExcelTime
-
-	if t.Before(excelMinTime1900) {
+func timeToExcelTime(t time.Time, date1904 bool) (float64, error) {
+	date := excelMinTime1900
+	if date1904 {
+		date = excel1904Epoc
+	}
+	if t.Before(date) {
 		return 0, nil
 	}
-
-	tt := t
-	diff := t.Sub(excelMinTime1900)
-	result := float64(0)
-
+	tt, diff, result := t, t.Sub(date), 0.0
 	for diff >= maxDuration {
 		result += float64(maxDuration / dayNanoseconds)
 		tt = tt.Add(-maxDuration)
-		diff = tt.Sub(excelMinTime1900)
+		diff = tt.Sub(date)
 	}
 
 	rem := diff % dayNanoseconds
@@ -57,7 +55,7 @@ func timeToExcelTime(t time.Time) (float64, error) {
 	// Microsoft intentionally included this bug in Excel so that it would remain compatible with the spreadsheet
 	// program that had the majority market share at the time; Lotus 1-2-3.
 	// https://www.myonlinetraininghub.com/excel-date-and-time
-	if t.After(excelBuggyPeriodStart) {
+	if !date1904 && t.After(excelBuggyPeriodStart) {
 		result++
 	}
 	return result, nil
diff --git a/date_test.go b/date_test.go
index cc21e58..4091e37 100644
--- a/date_test.go
+++ b/date_test.go
@@ -40,7 +40,7 @@ var excelTimeInputList = []dateTest{
 func TestTimeToExcelTime(t *testing.T) {
 	for i, test := range trueExpectedDateList {
 		t.Run(fmt.Sprintf("TestData%d", i+1), func(t *testing.T) {
-			excelTime, err := timeToExcelTime(test.GoValue)
+			excelTime, err := timeToExcelTime(test.GoValue, false)
 			assert.NoError(t, err)
 			assert.Equalf(t, test.ExcelValue, excelTime,
 				"Time: %s", test.GoValue.String())
@@ -55,7 +55,7 @@ func TestTimeToExcelTime_Timezone(t *testing.T) {
 	}
 	for i, test := range trueExpectedDateList {
 		t.Run(fmt.Sprintf("TestData%d", i+1), func(t *testing.T) {
-			_, err := timeToExcelTime(test.GoValue.In(location))
+			_, err := timeToExcelTime(test.GoValue.In(location), false)
 			assert.NoError(t, err)
 		})
 	}
@@ -71,21 +71,34 @@ func TestTimeFromExcelTime(t *testing.T) {
 		for min := 0; min < 60; min++ {
 			for sec := 0; sec < 60; sec++ {
 				date := time.Date(2021, time.December, 30, hour, min, sec, 0, time.UTC)
-				excelTime, err := timeToExcelTime(date)
+				// Test use 1900 date system
+				excel1900Time, err := timeToExcelTime(date, false)
 				assert.NoError(t, err)
-				dateOut := timeFromExcelTime(excelTime, false)
-				assert.EqualValues(t, hour, dateOut.Hour())
-				assert.EqualValues(t, min, dateOut.Minute())
-				assert.EqualValues(t, sec, dateOut.Second())
+				date1900Out := timeFromExcelTime(excel1900Time, false)
+				assert.EqualValues(t, hour, date1900Out.Hour())
+				assert.EqualValues(t, min, date1900Out.Minute())
+				assert.EqualValues(t, sec, date1900Out.Second())
+				// Test use 1904 date system
+				excel1904Time, err := timeToExcelTime(date, true)
+				assert.NoError(t, err)
+				date1904Out := timeFromExcelTime(excel1904Time, true)
+				assert.EqualValues(t, hour, date1904Out.Hour())
+				assert.EqualValues(t, min, date1904Out.Minute())
+				assert.EqualValues(t, sec, date1904Out.Second())
 			}
 		}
 	}
 }
 
 func TestTimeFromExcelTime_1904(t *testing.T) {
-	_, _ = shiftJulianToNoon(1, -0.6)
-	timeFromExcelTime(61, true)
-	timeFromExcelTime(62, true)
+	julianDays, julianFraction := shiftJulianToNoon(1, -0.6)
+	assert.Equal(t, julianDays, 0.0)
+	assert.Equal(t, julianFraction, 0.9)
+	julianDays, julianFraction = shiftJulianToNoon(1, 0.1)
+	assert.Equal(t, julianDays, 1.0)
+	assert.Equal(t, julianFraction, 0.6)
+	assert.Equal(t, timeFromExcelTime(61, true), time.Date(1904, time.March, 2, 0, 0, 0, 0, time.UTC))
+	assert.Equal(t, timeFromExcelTime(62, true), time.Date(1904, time.March, 3, 0, 0, 0, 0, time.UTC))
 }
 
 func TestExcelDateToTime(t *testing.T) {
diff --git a/merge.go b/merge.go
index 376b68b..0f57826 100644
--- a/merge.go
+++ b/merge.go
@@ -11,9 +11,7 @@
 
 package excelize
 
-import (
-	"strings"
-)
+import "strings"
 
 // Rect gets merged cell rectangle coordinates sequence.
 func (mc *xlsxMergeCell) Rect() ([]int, error) {
@@ -70,8 +68,7 @@ func (f *File) MergeCell(sheet, hCell, vCell string) error {
 		ws.MergeCells = &xlsxMergeCells{Cells: []*xlsxMergeCell{{Ref: ref, rect: rect}}}
 	}
 	ws.MergeCells.Count = len(ws.MergeCells.Cells)
-	styleID, _ := f.GetCellStyle(sheet, hCell)
-	return f.SetCellStyle(sheet, hCell, vCell, styleID)
+	return err
 }
 
 // UnmergeCell provides a function to unmerge a given coordinate area.
diff --git a/numfmt.go b/numfmt.go
index 5503027..2052fd9 100644
--- a/numfmt.go
+++ b/numfmt.go
@@ -939,10 +939,11 @@ func (nf *numberFormat) textHandler() (result string) {
 // getValueSectionType returns its applicable number format expression section
 // based on the given value.
 func (nf *numberFormat) getValueSectionType(value string) (float64, string) {
-	number, err := strconv.ParseFloat(value, 64)
-	if err != nil {
-		return number, nfp.TokenSectionText
+	isNum, _ := isNumeric(value)
+	if !isNum {
+		return 0, nfp.TokenSectionText
 	}
+	number, _ := strconv.ParseFloat(value, 64)
 	if number > 0 {
 		return number, nfp.TokenSectionPositive
 	}
diff --git a/rows_test.go b/rows_test.go
index ae30838..014b2d8 100644
--- a/rows_test.go
+++ b/rows_test.go
@@ -928,6 +928,11 @@ func TestSetRowStyle(t *testing.T) {
 	cellStyleID, err := f.GetCellStyle("Sheet1", "B2")
 	assert.NoError(t, err)
 	assert.Equal(t, style2, cellStyleID)
+	// Test cell inheritance rows style
+	assert.NoError(t, f.SetCellValue("Sheet1", "C1", nil))
+	cellStyleID, err = f.GetCellStyle("Sheet1", "C1")
+	assert.NoError(t, err)
+	assert.Equal(t, style2, cellStyleID)
 	assert.NoError(t, f.SaveAs(filepath.Join("test", "TestSetRowStyle.xlsx")))
 }
 
diff --git a/stream.go b/stream.go
index c2eda68..e1a12be 100644
--- a/stream.go
+++ b/stream.go
@@ -440,7 +440,11 @@ func (sw *StreamWriter) setCellValFunc(c *xlsxC, val interface{}) (err error) {
 		c.T, c.V = setCellDuration(val)
 	case time.Time:
 		var isNum bool
-		c.T, c.V, isNum, err = setCellTime(val)
+		date1904, wb := false, sw.File.workbookReader()
+		if wb != nil && wb.WorkbookPr != nil {
+			date1904 = wb.WorkbookPr.Date1904
+		}
+		c.T, c.V, isNum, err = setCellTime(val, date1904)
 		if isNum && c.S == 0 {
 			style, _ := sw.File.NewStyle(&Style{NumFmt: 22})
 			c.S = style