From f6f14f507ee1adf4883cb1b12f27932a63afb286 Mon Sep 17 00:00:00 2001
From: three <three3q@qq.com>
Date: Fri, 13 Aug 2021 01:32:44 +0800
Subject: [PATCH] Speed up merge cells

---
 adjust.go           |   8 +-
 adjust_test.go      |   4 +
 calc.go             |  12 +--
 cell.go             |  31 +++++--
 col.go              |   6 +-
 lib.go              |   5 +-
 merge.go            | 217 ++++++++++++++++++++++++++++++--------------
 merge_test.go       |  34 ++++---
 picture.go          |   2 +
 pivotTable.go       |   2 +-
 rows.go             |   4 +-
 sheet.go            |   3 +
 xmlSharedStrings.go |  22 +----
 xmlWorksheet.go     |   7 +-
 14 files changed, 227 insertions(+), 130 deletions(-)

diff --git a/adjust.go b/adjust.go
index 1fe6663..9f2176f 100644
--- a/adjust.go
+++ b/adjust.go
@@ -145,7 +145,7 @@ func (f *File) adjustAutoFilter(ws *xlsxWorksheet, dir adjustDirection, num, off
 		return nil
 	}
 
-	coordinates, err := f.areaRefToCoordinates(ws.AutoFilter.Ref)
+	coordinates, err := areaRefToCoordinates(ws.AutoFilter.Ref)
 	if err != nil {
 		return err
 	}
@@ -199,7 +199,7 @@ func (f *File) adjustMergeCells(ws *xlsxWorksheet, dir adjustDirection, num, off
 
 	for i := 0; i < len(ws.MergeCells.Cells); i++ {
 		areaData := ws.MergeCells.Cells[i]
-		coordinates, err := f.areaRefToCoordinates(areaData.Ref)
+		coordinates, err := areaRefToCoordinates(areaData.Ref)
 		if err != nil {
 			return err
 		}
@@ -219,7 +219,7 @@ func (f *File) adjustMergeCells(ws *xlsxWorksheet, dir adjustDirection, num, off
 			x1 = f.adjustMergeCellsHelper(x1, num, offset)
 			x2 = f.adjustMergeCellsHelper(x2, num, offset)
 		}
-		if x1 == x2 && y1 == y2 {
+		if x1 == x2 && y1 == y2 && i >= 0 {
 			f.deleteMergeCell(ws, i)
 			i--
 		}
@@ -234,7 +234,7 @@ func (f *File) adjustMergeCells(ws *xlsxWorksheet, dir adjustDirection, num, off
 // compare and calculate cell axis by the given pivot, operation axis and
 // offset.
 func (f *File) adjustMergeCellsHelper(pivot, num, offset int) int {
-	if pivot >= num {
+	if pivot > num {
 		pivot += offset
 		if pivot < 1 {
 			return 1
diff --git a/adjust_test.go b/adjust_test.go
index ced091d..f56f763 100644
--- a/adjust_test.go
+++ b/adjust_test.go
@@ -84,6 +84,10 @@ func TestAdjustHelper(t *testing.T) {
 	assert.EqualError(t, f.adjustHelper("SheetN", rows, 0, 0), "sheet SheetN is not exist")
 }
 
+func TestAdjustMergeCellsHelper(t *testing.T) {
+	assert.Equal(t, 1, NewFile().adjustMergeCellsHelper(1, 0, -2))
+}
+
 func TestAdjustCalcChain(t *testing.T) {
 	f := NewFile()
 	f.CalcChain = &xlsxCalcChain{
diff --git a/calc.go b/calc.go
index cd7fa97..a03520b 100644
--- a/calc.go
+++ b/calc.go
@@ -5103,11 +5103,11 @@ func (fn *formulaFuncs) kth(name string, argsList *list.List) formulaArg {
 		return newErrorFormulaArg(formulaErrorVALUE, fmt.Sprintf("%s requires 2 arguments", name))
 	}
 	array := argsList.Front().Value.(formulaArg).ToList()
-	kArg := argsList.Back().Value.(formulaArg).ToNumber()
-	if kArg.Type != ArgNumber {
-		return kArg
+	argK := argsList.Back().Value.(formulaArg).ToNumber()
+	if argK.Type != ArgNumber {
+		return argK
 	}
-	k := int(kArg.Number)
+	k := int(argK.Number)
 	if k < 1 {
 		return newErrorFormulaArg(formulaErrorNUM, "k should be > 0")
 	}
@@ -7177,7 +7177,7 @@ func (fn *formulaFuncs) VLOOKUP(argsList *list.List) formulaArg {
 func vlookupBinarySearch(tableArray, lookupValue formulaArg) (matchIdx int, wasExact bool) {
 	var low, high, lastMatchIdx int = 0, len(tableArray.Matrix) - 1, -1
 	for low <= high {
-		var mid int = low + (high-low)/2
+		mid := low + (high-low)/2
 		mtx := tableArray.Matrix[mid]
 		lhs := mtx[0]
 		switch lookupValue.Type {
@@ -7216,7 +7216,7 @@ func vlookupBinarySearch(tableArray, lookupValue formulaArg) (matchIdx int, wasE
 func hlookupBinarySearch(row []formulaArg, lookupValue formulaArg) (matchIdx int, wasExact bool) {
 	var low, high, lastMatchIdx int = 0, len(row) - 1, -1
 	for low <= high {
-		var mid int = low + (high-low)/2
+		mid := low + (high-low)/2
 		mtx := row[mid]
 		result := compareFormulaArg(mtx, lookupValue, false, false)
 		if result == criteriaEq {
diff --git a/cell.go b/cell.go
index 9200d13..6ad5f44 100644
--- a/cell.go
+++ b/cell.go
@@ -101,6 +101,28 @@ func (f *File) SetCellValue(sheet, axis string, value interface{}) error {
 	return err
 }
 
+// String extracts characters from a string item.
+func (x xlsxSI) String() string {
+	if len(x.R) > 0 {
+		var rows strings.Builder
+		for _, s := range x.R {
+			if s.T != nil {
+				rows.WriteString(s.T.Val)
+			}
+		}
+		return bstrUnmarshal(rows.String())
+	}
+	if x.T != nil {
+		return bstrUnmarshal(x.T.Val)
+	}
+	return ""
+}
+
+// hasValue determine if cell non-blank value.
+func (c *xlsxC) hasValue() bool {
+	return c.S != 0 || c.V != "" || c.F != nil || c.T != ""
+}
+
 // setCellIntFunc is a wrapper of SetCellInt.
 func (f *File) setCellIntFunc(sheet, axis string, value interface{}) error {
 	var err error
@@ -431,13 +453,11 @@ func (f *File) GetCellHyperLink(sheet, axis string) (bool, string, error) {
 	if _, _, err := SplitCellName(axis); err != nil {
 		return false, "", err
 	}
-
 	ws, err := f.workSheetReader(sheet)
 	if err != nil {
 		return false, "", err
 	}
-	axis, err = f.mergeCellsParser(ws, axis)
-	if err != nil {
+	if axis, err = f.mergeCellsParser(ws, axis); err != nil {
 		return false, "", err
 	}
 	if ws.Hyperlinks != nil {
@@ -485,8 +505,7 @@ func (f *File) SetCellHyperLink(sheet, axis, link, linkType string, opts ...Hype
 	if err != nil {
 		return err
 	}
-	axis, err = f.mergeCellsParser(ws, axis)
-	if err != nil {
+	if axis, err = f.mergeCellsParser(ws, axis); err != nil {
 		return err
 	}
 
@@ -932,7 +951,7 @@ func (f *File) checkCellInArea(cell, area string) (bool, error) {
 	if len(rng) != 2 {
 		return false, err
 	}
-	coordinates, err := f.areaRefToCoordinates(area)
+	coordinates, err := areaRefToCoordinates(area)
 	if err != nil {
 		return false, err
 	}
diff --git a/col.go b/col.go
index 088fac9..7fbeeba 100644
--- a/col.go
+++ b/col.go
@@ -616,10 +616,10 @@ func (f *File) positionObjectPixels(sheet string, col, row, x1, y1, width, heigh
 // getColWidth provides a function to get column width in pixels by given
 // sheet name and column number.
 func (f *File) getColWidth(sheet string, col int) int {
-	xlsx, _ := f.workSheetReader(sheet)
-	if xlsx.Cols != nil {
+	ws, _ := f.workSheetReader(sheet)
+	if ws.Cols != nil {
 		var width float64
-		for _, v := range xlsx.Cols.Col {
+		for _, v := range ws.Cols.Col {
 			if v.Min <= col && col <= v.Max {
 				width = v.Width
 			}
diff --git a/lib.go b/lib.go
index 7db14c4..912f738 100644
--- a/lib.go
+++ b/lib.go
@@ -221,12 +221,11 @@ func CoordinatesToCellName(col, row int, abs ...bool) (string, error) {
 
 // areaRefToCoordinates provides a function to convert area reference to a
 // pair of coordinates.
-func (f *File) areaRefToCoordinates(ref string) ([]int, error) {
+func areaRefToCoordinates(ref string) ([]int, error) {
 	rng := strings.Split(strings.Replace(ref, "$", "", -1), ":")
 	if len(rng) < 2 {
 		return nil, ErrParameterInvalid
 	}
-
 	return areaRangeToCoordinates(rng[0], rng[1])
 }
 
@@ -290,7 +289,7 @@ func (f *File) flatSqref(sqref string) (cells map[int][][]int, err error) {
 			}
 			cells[col] = append(cells[col], []int{col, row})
 		case 2:
-			if coordinates, err = f.areaRefToCoordinates(ref); err != nil {
+			if coordinates, err = areaRefToCoordinates(ref); err != nil {
 				return
 			}
 			_ = sortCoordinates(coordinates)
diff --git a/merge.go b/merge.go
index 7769b89..1cd8acd 100644
--- a/merge.go
+++ b/merge.go
@@ -11,10 +11,16 @@
 
 package excelize
 
-import (
-	"fmt"
-	"strings"
-)
+import "strings"
+
+// Rect gets merged cell rectangle coordinates sequence.
+func (mc *xlsxMergeCell) Rect() ([]int, error) {
+	var err error
+	if mc.rect == nil {
+		mc.rect, err = areaRefToCoordinates(mc.Ref)
+	}
+	return mc.rect, err
+}
 
 // MergeCell provides a function to merge cells by given coordinate area and
 // sheet name. Merging cells only keeps the upper-left cell value, and
@@ -24,7 +30,9 @@ import (
 //    err := f.MergeCell("Sheet1", "D3", "E9")
 //
 // If you create a merged cell that overlaps with another existing merged cell,
-// those merged cells that already exist will be removed.
+// those merged cells that already exist will be removed. The cell coordinates
+// tuple after merging in the following range will be: A1(x3,y1) D1(x2,y1)
+// A8(x3,y4) D8(x2,y4)
 //
 //                 B1(x1,y1)      D1(x2,y1)
 //               +------------------------+
@@ -39,15 +47,15 @@ import (
 //    +------------------------+
 //
 func (f *File) MergeCell(sheet, hcell, vcell string) error {
-	rect1, err := f.areaRefToCoordinates(hcell + ":" + vcell)
+	rect, err := areaRefToCoordinates(hcell + ":" + vcell)
 	if err != nil {
 		return err
 	}
 	// Correct the coordinate area, such correct C1:B3 to B1:C3.
-	_ = sortCoordinates(rect1)
+	_ = sortCoordinates(rect)
 
-	hcell, _ = CoordinatesToCellName(rect1[0], rect1[1])
-	vcell, _ = CoordinatesToCellName(rect1[2], rect1[3])
+	hcell, _ = CoordinatesToCellName(rect[0], rect[1])
+	vcell, _ = CoordinatesToCellName(rect[2], rect[3])
 
 	ws, err := f.workSheetReader(sheet)
 	if err != nil {
@@ -55,49 +63,9 @@ func (f *File) MergeCell(sheet, hcell, vcell string) error {
 	}
 	ref := hcell + ":" + vcell
 	if ws.MergeCells != nil {
-		for i := 0; i < len(ws.MergeCells.Cells); i++ {
-			cellData := ws.MergeCells.Cells[i]
-			if cellData == nil {
-				continue
-			}
-			cc := strings.Split(cellData.Ref, ":")
-			if len(cc) != 2 {
-				return fmt.Errorf("invalid area %q", cellData.Ref)
-			}
-
-			rect2, err := f.areaRefToCoordinates(cellData.Ref)
-			if err != nil {
-				return err
-			}
-
-			// Delete the merged cells of the overlapping area.
-			if isOverlap(rect1, rect2) {
-				ws.MergeCells.Cells = append(ws.MergeCells.Cells[:i], ws.MergeCells.Cells[i+1:]...)
-				i--
-
-				if rect1[0] > rect2[0] {
-					rect1[0], rect2[0] = rect2[0], rect1[0]
-				}
-
-				if rect1[2] < rect2[2] {
-					rect1[2], rect2[2] = rect2[2], rect1[2]
-				}
-
-				if rect1[1] > rect2[1] {
-					rect1[1], rect2[1] = rect2[1], rect1[1]
-				}
-
-				if rect1[3] < rect2[3] {
-					rect1[3], rect2[3] = rect2[3], rect1[3]
-				}
-				hcell, _ = CoordinatesToCellName(rect1[0], rect1[1])
-				vcell, _ = CoordinatesToCellName(rect1[2], rect1[3])
-				ref = hcell + ":" + vcell
-			}
-		}
-		ws.MergeCells.Cells = append(ws.MergeCells.Cells, &xlsxMergeCell{Ref: ref})
+		ws.MergeCells.Cells = append(ws.MergeCells.Cells, &xlsxMergeCell{Ref: ref, rect: rect})
 	} else {
-		ws.MergeCells = &xlsxMergeCells{Cells: []*xlsxMergeCell{{Ref: ref}}}
+		ws.MergeCells = &xlsxMergeCells{Cells: []*xlsxMergeCell{{Ref: ref, rect: rect}}}
 	}
 	ws.MergeCells.Count = len(ws.MergeCells.Cells)
 	return err
@@ -114,7 +82,7 @@ func (f *File) UnmergeCell(sheet string, hcell, vcell string) error {
 	if err != nil {
 		return err
 	}
-	rect1, err := f.areaRefToCoordinates(hcell + ":" + vcell)
+	rect1, err := areaRefToCoordinates(hcell + ":" + vcell)
 	if err != nil {
 		return err
 	}
@@ -126,26 +94,19 @@ func (f *File) UnmergeCell(sheet string, hcell, vcell string) error {
 	if ws.MergeCells == nil {
 		return nil
 	}
-
+	if err = f.mergeOverlapCells(ws); err != nil {
+		return err
+	}
 	i := 0
-	for _, cellData := range ws.MergeCells.Cells {
-		if cellData == nil {
+	for _, mergeCell := range ws.MergeCells.Cells {
+		if mergeCell == nil {
 			continue
 		}
-		cc := strings.Split(cellData.Ref, ":")
-		if len(cc) != 2 {
-			return fmt.Errorf("invalid area %q", cellData.Ref)
-		}
-
-		rect2, err := f.areaRefToCoordinates(cellData.Ref)
-		if err != nil {
-			return err
-		}
-
+		rect2, _ := areaRefToCoordinates(mergeCell.Ref)
 		if isOverlap(rect1, rect2) {
 			continue
 		}
-		ws.MergeCells.Cells[i] = cellData
+		ws.MergeCells.Cells[i] = mergeCell
 		i++
 	}
 	ws.MergeCells.Cells = ws.MergeCells.Cells[:i]
@@ -165,8 +126,10 @@ func (f *File) GetMergeCells(sheet string) ([]MergeCell, error) {
 		return mergeCells, err
 	}
 	if ws.MergeCells != nil {
+		if err = f.mergeOverlapCells(ws); err != nil {
+			return mergeCells, err
+		}
 		mergeCells = make([]MergeCell, 0, len(ws.MergeCells.Cells))
-
 		for i := range ws.MergeCells.Cells {
 			ref := ws.MergeCells.Cells[i].Ref
 			axis := strings.Split(ref, ":")[0]
@@ -174,10 +137,128 @@ func (f *File) GetMergeCells(sheet string) ([]MergeCell, error) {
 			mergeCells = append(mergeCells, []string{ref, val})
 		}
 	}
-
 	return mergeCells, err
 }
 
+// overlapRange calculate overlap range of merged cells, and returns max
+// column and rows of the range.
+func overlapRange(ws *xlsxWorksheet) (row, col int, err error) {
+	var rect []int
+	for _, mergeCell := range ws.MergeCells.Cells {
+		if mergeCell == nil {
+			continue
+		}
+		if rect, err = mergeCell.Rect(); err != nil {
+			return
+		}
+		x1, y1, x2, y2 := rect[0], rect[1], rect[2], rect[3]
+		if x1 > col {
+			col = x1
+		}
+		if x2 > col {
+			col = x2
+		}
+		if y1 > row {
+			row = y1
+		}
+		if y2 > row {
+			row = y2
+		}
+	}
+	return
+}
+
+// flatMergedCells convert merged cells range reference to cell-matrix.
+func flatMergedCells(ws *xlsxWorksheet, matrix [][]*xlsxMergeCell) error {
+	for i, cell := range ws.MergeCells.Cells {
+		rect, err := cell.Rect()
+		if err != nil {
+			return err
+		}
+		x1, y1, x2, y2 := rect[0]-1, rect[1]-1, rect[2]-1, rect[3]-1
+		var overlapCells []*xlsxMergeCell
+		for x := x1; x <= x2; x++ {
+			for y := y1; y <= y2; y++ {
+				if matrix[x][y] != nil {
+					overlapCells = append(overlapCells, matrix[x][y])
+				}
+				matrix[x][y] = cell
+			}
+		}
+		if len(overlapCells) != 0 {
+			newCell := cell
+			for _, overlapCell := range overlapCells {
+				newCell = mergeCell(cell, overlapCell)
+			}
+			newRect, _ := newCell.Rect()
+			x1, y1, x2, y2 := newRect[0]-1, newRect[1]-1, newRect[2]-1, newRect[3]-1
+			for x := x1; x <= x2; x++ {
+				for y := y1; y <= y2; y++ {
+					matrix[x][y] = newCell
+				}
+			}
+			ws.MergeCells.Cells[i] = newCell
+		}
+	}
+	return nil
+}
+
+// mergeOverlapCells merge overlap cells.
+func (f *File) mergeOverlapCells(ws *xlsxWorksheet) error {
+	rows, cols, err := overlapRange(ws)
+	if err != nil {
+		return err
+	}
+	if rows == 0 || cols == 0 {
+		return nil
+	}
+	matrix := make([][]*xlsxMergeCell, cols)
+	for i := range matrix {
+		matrix[i] = make([]*xlsxMergeCell, rows)
+	}
+	_ = flatMergedCells(ws, matrix)
+	mergeCells := ws.MergeCells.Cells[:0]
+	for _, cell := range ws.MergeCells.Cells {
+		rect, _ := cell.Rect()
+		x1, y1, x2, y2 := rect[0]-1, rect[1]-1, rect[2]-1, rect[3]-1
+		if matrix[x1][y1] == cell {
+			mergeCells = append(mergeCells, cell)
+			for x := x1; x <= x2; x++ {
+				for y := y1; y <= y2; y++ {
+					matrix[x][y] = nil
+				}
+			}
+		}
+	}
+	ws.MergeCells.Count, ws.MergeCells.Cells = len(mergeCells), mergeCells
+	return nil
+}
+
+// mergeCell merge two cells.
+func mergeCell(cell1, cell2 *xlsxMergeCell) *xlsxMergeCell {
+	rect1, _ := cell1.Rect()
+	rect2, _ := cell2.Rect()
+
+	if rect1[0] > rect2[0] {
+		rect1[0], rect2[0] = rect2[0], rect1[0]
+	}
+
+	if rect1[2] < rect2[2] {
+		rect1[2], rect2[2] = rect2[2], rect1[2]
+	}
+
+	if rect1[1] > rect2[1] {
+		rect1[1], rect2[1] = rect2[1], rect1[1]
+	}
+
+	if rect1[3] < rect2[3] {
+		rect1[3], rect2[3] = rect2[3], rect1[3]
+	}
+	hcell, _ := CoordinatesToCellName(rect1[0], rect1[1])
+	vcell, _ := CoordinatesToCellName(rect1[2], rect1[3])
+	return &xlsxMergeCell{rect: rect1, Ref: hcell + ":" + vcell}
+}
+
 // MergeCell define a merged cell data.
 // It consists of the following structure.
 // example: []string{"D4:E10", "cell value"}
diff --git a/merge_test.go b/merge_test.go
index 41c122c..a370126 100644
--- a/merge_test.go
+++ b/merge_test.go
@@ -27,7 +27,7 @@ func TestMergeCell(t *testing.T) {
 	assert.NoError(t, f.SetCellHyperLink("Sheet1", "J11", "https://github.com/xuri/excelize", "External"))
 	assert.NoError(t, f.SetCellFormula("Sheet1", "G12", "SUM(Sheet1!B19,Sheet1!C19)"))
 	value, err := f.GetCellValue("Sheet1", "H11")
-	assert.Equal(t, "0.5", value)
+	assert.Equal(t, "100", value)
 	assert.NoError(t, err)
 	value, err = f.GetCellValue("Sheet2", "A6") // Merged cell ref is single coordinate.
 	assert.Equal(t, "", value)
@@ -75,16 +75,24 @@ func TestMergeCell(t *testing.T) {
 	assert.True(t, ok)
 	ws.(*xlsxWorksheet).MergeCells = &xlsxMergeCells{Cells: []*xlsxMergeCell{nil, nil}}
 	assert.NoError(t, f.MergeCell("Sheet1", "A2", "B3"))
+}
 
-	ws, ok = f.Sheet.Load("xl/worksheets/sheet1.xml")
-	assert.True(t, ok)
-	ws.(*xlsxWorksheet).MergeCells = &xlsxMergeCells{Cells: []*xlsxMergeCell{{Ref: "A1"}}}
-	assert.EqualError(t, f.MergeCell("Sheet1", "A2", "B3"), `invalid area "A1"`)
+func TestMergeCellOverlap(t *testing.T) {
+	f := NewFile()
+	assert.NoError(t, f.MergeCell("Sheet1", "A1", "C2"))
+	assert.NoError(t, f.MergeCell("Sheet1", "B2", "D3"))
+	assert.NoError(t, f.SaveAs(filepath.Join("test", "TestMergeCellOverlap.xlsx")))
 
-	ws, ok = f.Sheet.Load("xl/worksheets/sheet1.xml")
-	assert.True(t, ok)
-	ws.(*xlsxWorksheet).MergeCells = &xlsxMergeCells{Cells: []*xlsxMergeCell{{Ref: "A:A"}}}
-	assert.EqualError(t, f.MergeCell("Sheet1", "A2", "B3"), `cannot convert cell "A" to coordinates: invalid cell name "A"`)
+	f, err := OpenFile(filepath.Join("test", "TestMergeCellOverlap.xlsx"))
+	if !assert.NoError(t, err) {
+		t.FailNow()
+	}
+	mc, err := f.GetMergeCells("Sheet1")
+	assert.NoError(t, err)
+	assert.Equal(t, 1, len(mc))
+	assert.Equal(t, "A1", mc[0].GetStartAxis())
+	assert.Equal(t, "D3", mc[0].GetEndAxis())
+	assert.Equal(t, "", mc[0].GetCellValue())
 }
 
 func TestGetMergeCells(t *testing.T) {
@@ -173,11 +181,15 @@ func TestUnmergeCell(t *testing.T) {
 	ws, ok = f.Sheet.Load("xl/worksheets/sheet1.xml")
 	assert.True(t, ok)
 	ws.(*xlsxWorksheet).MergeCells = &xlsxMergeCells{Cells: []*xlsxMergeCell{{Ref: "A1"}}}
-	assert.EqualError(t, f.UnmergeCell("Sheet1", "A2", "B3"), `invalid area "A1"`)
+	assert.EqualError(t, f.UnmergeCell("Sheet1", "A2", "B3"), "parameter is invalid")
 
 	ws, ok = f.Sheet.Load("xl/worksheets/sheet1.xml")
 	assert.True(t, ok)
 	ws.(*xlsxWorksheet).MergeCells = &xlsxMergeCells{Cells: []*xlsxMergeCell{{Ref: "A:A"}}}
 	assert.EqualError(t, f.UnmergeCell("Sheet1", "A2", "B3"), `cannot convert cell "A" to coordinates: invalid cell name "A"`)
-
+}
+
+func TestFlatMergedCells(t *testing.T) {
+	ws := &xlsxWorksheet{MergeCells: &xlsxMergeCells{Cells: []*xlsxMergeCell{{Ref: "A1"}}}}
+	assert.EqualError(t, flatMergedCells(ws, [][]*xlsxMergeCell{}), "parameter is invalid")
 }
diff --git a/picture.go b/picture.go
index d22a708..c37899e 100644
--- a/picture.go
+++ b/picture.go
@@ -148,6 +148,7 @@ func (f *File) AddPictureFromBytes(sheet, cell, format, name, extension string,
 	if err != nil {
 		return err
 	}
+	ws.Lock()
 	// Add first picture for given sheet, create xl/drawings/ and xl/drawings/_rels/ folder.
 	drawingID := f.countDrawings() + 1
 	drawingXML := "xl/drawings/drawing" + strconv.Itoa(drawingID) + ".xml"
@@ -162,6 +163,7 @@ func (f *File) AddPictureFromBytes(sheet, cell, format, name, extension string,
 		}
 		drawingHyperlinkRID = f.addRels(drawingRels, SourceRelationshipHyperLink, formatSet.Hyperlink, hyperlinkType)
 	}
+	ws.Unlock()
 	err = f.addDrawingPicture(sheet, drawingXML, cell, name, img.Width, img.Height, drawingRID, drawingHyperlinkRID, formatSet)
 	if err != nil {
 		return err
diff --git a/pivotTable.go b/pivotTable.go
index 07cf84c..0b0e5af 100644
--- a/pivotTable.go
+++ b/pivotTable.go
@@ -198,7 +198,7 @@ func (f *File) adjustRange(rangeStr string) (string, []int, error) {
 		return "", []int{}, ErrParameterInvalid
 	}
 	trimRng := strings.Replace(rng[1], "$", "", -1)
-	coordinates, err := f.areaRefToCoordinates(trimRng)
+	coordinates, err := areaRefToCoordinates(trimRng)
 	if err != nil {
 		return rng[0], []int{}, err
 	}
diff --git a/rows.go b/rows.go
index fcd3c1a..5fa2cb4 100644
--- a/rows.go
+++ b/rows.go
@@ -614,7 +614,7 @@ func (f *File) duplicateMergeCells(sheet string, ws *xlsxWorksheet, row, row2 in
 		row++
 	}
 	for _, rng := range ws.MergeCells.Cells {
-		coordinates, err := f.areaRefToCoordinates(rng.Ref)
+		coordinates, err := areaRefToCoordinates(rng.Ref)
 		if err != nil {
 			return err
 		}
@@ -624,7 +624,7 @@ func (f *File) duplicateMergeCells(sheet string, ws *xlsxWorksheet, row, row2 in
 	}
 	for i := 0; i < len(ws.MergeCells.Cells); i++ {
 		areaData := ws.MergeCells.Cells[i]
-		coordinates, _ := f.areaRefToCoordinates(areaData.Ref)
+		coordinates, _ := areaRefToCoordinates(areaData.Ref)
 		x1, y1, x2, y2 := coordinates[0], coordinates[1], coordinates[2], coordinates[3]
 		if y1 == y2 && y1 == row {
 			from, _ := CoordinatesToCellName(x1, row2)
diff --git a/sheet.go b/sheet.go
index 756eb81..1c4b355 100644
--- a/sheet.go
+++ b/sheet.go
@@ -158,6 +158,9 @@ func (f *File) workSheetWriter() {
 	f.Sheet.Range(func(p, ws interface{}) bool {
 		if ws != nil {
 			sheet := ws.(*xlsxWorksheet)
+			if sheet.MergeCells != nil && len(sheet.MergeCells.Cells) > 0 {
+				_ = f.mergeOverlapCells(sheet)
+			}
 			for k, v := range sheet.SheetData.Row {
 				sheet.SheetData.Row[k].C = trimCell(v.C)
 			}
diff --git a/xmlSharedStrings.go b/xmlSharedStrings.go
index 816c931..e505d26 100644
--- a/xmlSharedStrings.go
+++ b/xmlSharedStrings.go
@@ -11,10 +11,7 @@
 
 package excelize
 
-import (
-	"encoding/xml"
-	"strings"
-)
+import "encoding/xml"
 
 // xlsxSST directly maps the sst element from the namespace
 // http://schemas.openxmlformats.org/spreadsheetml/2006/main. String values may
@@ -44,23 +41,6 @@ type xlsxSI struct {
 	PhoneticPr *xlsxPhoneticPr    `xml:"phoneticPr"`
 }
 
-// String extracts characters from a string item.
-func (x xlsxSI) String() string {
-	if len(x.R) > 0 {
-		var rows strings.Builder
-		for _, s := range x.R {
-			if s.T != nil {
-				rows.WriteString(s.T.Val)
-			}
-		}
-		return bstrUnmarshal(rows.String())
-	}
-	if x.T != nil {
-		return bstrUnmarshal(x.T.Val)
-	}
-	return ""
-}
-
 // xlsxR represents a run of rich text. A rich text run is a region of text
 // that share a common set of properties, such as formatting properties. The
 // properties are defined in the rPr element, and the text displayed to the
diff --git a/xmlWorksheet.go b/xmlWorksheet.go
index 4499546..697504e 100644
--- a/xmlWorksheet.go
+++ b/xmlWorksheet.go
@@ -399,7 +399,8 @@ type xlsxCustomSheetView struct {
 
 // xlsxMergeCell directly maps the mergeCell element. A single merged cell.
 type xlsxMergeCell struct {
-	Ref string `xml:"ref,attr,omitempty"`
+	Ref  string `xml:"ref,attr,omitempty"`
+	rect []int
 }
 
 // xlsxMergeCells directly maps the mergeCells element. This collection
@@ -468,10 +469,6 @@ type xlsxC struct {
 	IS *xlsxSI `xml:"is"`
 }
 
-func (c *xlsxC) hasValue() bool {
-	return c.S != 0 || c.V != "" || c.F != nil || c.T != ""
-}
-
 // xlsxF represents a formula for the cell. The formula expression is
 // contained in the character node of this element.
 type xlsxF struct {