Avoid looping over unused rows and columns in SetCellStyle.

The recent improvement to SetCellStyle still loops
over all the rows before the area, moving the area checks
into the loop is more concise and faster.

Since the loop now covers the correct area by construction,
the inner loop check checkCellInArea is no longer needed.

styles.go

@@ -2307,6 +2307,7 @@ func (f *File) SetCellStyle(sheet, hcell, vcell string, styleID int) {
 	vyAxis := vrow - 1
 	vxAxis := TitleToNumber(vcol)
 
+	// Correct the coordinate area, such correct C1:B3 to B1:C3.
 	if vxAxis < hxAxis {
 		hcell, vcell = vcell, hcell
 		vxAxis, hxAxis = hxAxis, vxAxis
@@ -2317,32 +2318,14 @@ func (f *File) SetCellStyle(sheet, hcell, vcell string, styleID int) {
 		vyAxis, hyAxis = hyAxis, vyAxis
 	}
 
-	// Correct the coordinate area, such correct C1:B3 to B1:C3.
-	hcell = ToAlphaString(hxAxis) + strconv.Itoa(hyAxis+1)
-	vcell = ToAlphaString(vxAxis) + strconv.Itoa(vyAxis+1)
-
 	xlsx := f.workSheetReader(sheet)
 
 	completeRow(xlsx, vyAxis+1, vxAxis+1)
 	completeCol(xlsx, vyAxis+1, vxAxis+1)
 
-	for r, row := range xlsx.SheetData.Row {
-		if r < hyAxis {
-			continue
-		} else if r > vyAxis {
-			break
-		}
-
-		for k, c := range row.C {
-			if k < hxAxis {
-				continue
-			} else if k > vxAxis {
-				break
-			}
-
-			if checkCellInArea(c.R, hcell+":"+vcell) {
-				xlsx.SheetData.Row[r].C[k].S = styleID
-			}
+	for r := hyAxis; r <= vyAxis; r++ {
+		for k := hxAxis; k <= vxAxis; k++ {
+			xlsx.SheetData.Row[r].C[k].S = styleID
 		}
 	}
 }