some improvments

internal/pdf/contentstream/contentstream.go

@@ -3,6 +3,7 @@ package contentstream
 import (
 	"bytes"
 	"fmt"
+	"strings"
 
 	"gitea.tecamino.com/paadi/pdfmerge/internal/pdf/core"
 )
@@ -111,7 +112,7 @@ func (s *ContentStreamParser) ExtractText() (string, error) {
 	}
 	inText := false
 	xPos, yPos := float64(-1), float64(-1)
-	txt := ""
+	var txt strings.Builder
 	for _, op := range *operations {
 		switch op.Operand {
 		case "BT":
@@ -122,7 +123,7 @@ func (s *ContentStreamParser) ExtractText() (string, error) {
 
 		if op.Operand == "Td" || op.Operand == "TD" || op.Operand == "T*" {
 			// Move to next line...
-			txt += "\n"
+			txt.WriteString("\n")
 		}
 		if op.Operand == "Tm" {
 			if len(op.Params) != 6 {
@@ -147,7 +148,7 @@ func (s *ContentStreamParser) ExtractText() (string, error) {
 			if yPos == -1 {
 				yPos = float64(*yfloat)
 			} else if yPos > float64(*yfloat) {
-				txt += "\n"
+				txt.WriteString("\n")
 				xPos = float64(*xfloat)
 				yPos = float64(*yfloat)
 				continue
@@ -155,7 +156,7 @@ func (s *ContentStreamParser) ExtractText() (string, error) {
 			if xPos == -1 {
 				xPos = float64(*xfloat)
 			} else if xPos < float64(*xfloat) {
-				txt += "\t"
+				txt.WriteString("\t")
 				xPos = float64(*xfloat)
 			}
 		}
@@ -170,14 +171,14 @@ func (s *ContentStreamParser) ExtractText() (string, error) {
 			for _, obj := range *paramList {
 				switch v := obj.(type) {
 				case *core.PdfObjectString:
-					txt += string(*v)
+					txt.WriteString(string(*v))
 				case *core.PdfObjectFloat:
 					if *v < -100 {
-						txt += " "
+						txt.WriteString(" ")
 					}
 				case *core.PdfObjectInteger:
 					if *v < -100 {
-						txt += " "
+						txt.WriteString(" ")
 					}
 				}
 			}
@@ -189,9 +190,9 @@ func (s *ContentStreamParser) ExtractText() (string, error) {
 			if !ok {
 				return "", fmt.Errorf("invalid parameter type, not string (%T)", op.Params[0])
 			}
-			txt += string(*param)
+			txt.WriteString(string(*param))
 		}
 	}
 
-	return txt, nil
+	return txt.String(), nil
 }

internal/pdf/contentstream/draw/bezier_curve.go

@@ -89,9 +89,9 @@ func NewCubicBezierPath() CubicBezierPath {
 	return bpath
 }
 
-func (this CubicBezierPath) AppendCurve(curve CubicBezierCurve) CubicBezierPath {
-	this.Curves = append(this.Curves, curve)
-	return this
+func (c CubicBezierPath) AppendCurve(curve CubicBezierCurve) CubicBezierPath {
+	c.Curves = append(c.Curves, curve)
+	return c
 }
 
 func (bpath CubicBezierPath) Copy() CubicBezierPath {

internal/pdf/contentstream/draw/path.go

@@ -11,36 +11,36 @@ func NewPath() Path {
 	return path
 }
 
-func (this Path) AppendPoint(point Point) Path {
-	this.Points = append(this.Points, point)
-	return this
+func (p Path) AppendPoint(point Point) Path {
+	p.Points = append(p.Points, point)
+	return p
 }
 
-func (this Path) RemovePoint(number int) Path {
-	if number < 1 || number > len(this.Points) {
-		return this
+func (p Path) RemovePoint(number int) Path {
+	if number < 1 || number > len(p.Points) {
+		return p
 	}
 
 	idx := number - 1
-	this.Points = append(this.Points[:idx], this.Points[idx+1:]...)
-	return this
+	p.Points = append(p.Points[:idx], p.Points[idx+1:]...)
+	return p
 }
 
-func (this Path) Length() int {
-	return len(this.Points)
+func (p Path) Length() int {
+	return len(p.Points)
 }
 
-func (this Path) GetPointNumber(number int) Point {
-	if number < 1 || number > len(this.Points) {
+func (p Path) GetPointNumber(number int) Point {
+	if number < 1 || number > len(p.Points) {
 		return Point{}
 	}
-	return this.Points[number-1]
+	return p.Points[number-1]
 }
 
-func (path Path) Copy() Path {
+func (p Path) Copy() Path {
 	pathcopy := Path{}
 	pathcopy.Points = []Point{}
-	for _, p := range path.Points {
+	for _, p := range p.Points {
 		pathcopy.Points = append(pathcopy.Points, p)
 	}
 	return pathcopy

internal/pdf/contentstream/draw/point.go

@@ -21,10 +21,10 @@ func (p Point) Add(dx, dy float64) Point {
 }
 
 // Add vector to a point.
-func (this Point) AddVector(v Vector) Point {
-	this.X += v.Dx
-	this.Y += v.Dy
-	return this
+func (p Point) AddVector(v Vector) Point {
+	p.X += v.Dx
+	p.Y += v.Dy
+	return p
 }
 
 func (p Point) String() string {

internal/pdf/contentstream/draw/vector.go

@@ -43,13 +43,13 @@ func (v Vector) Rotate(phi float64) Vector {
 }
 
 // Change the sign of the vector: -vector.
-func (this Vector) Flip() Vector {
-	mag := this.Magnitude()
-	theta := this.GetPolarAngle()
+func (v Vector) Flip() Vector {
+	mag := v.Magnitude()
+	theta := v.GetPolarAngle()
 
-	this.Dx = mag * math.Cos(theta+math.Pi)
-	this.Dy = mag * math.Sin(theta+math.Pi)
-	return this
+	v.Dx = mag * math.Cos(theta+math.Pi)
+	v.Dy = mag * math.Sin(theta+math.Pi)
+	return v
 }
 
 func (v Vector) FlipY() Vector {
@@ -62,19 +62,19 @@ func (v Vector) FlipX() Vector {
 	return v
 }
 
-func (this Vector) Scale(factor float64) Vector {
-	mag := this.Magnitude()
-	theta := this.GetPolarAngle()
+func (v Vector) Scale(factor float64) Vector {
+	mag := v.Magnitude()
+	theta := v.GetPolarAngle()
 
-	this.Dx = factor * mag * math.Cos(theta)
-	this.Dy = factor * mag * math.Sin(theta)
-	return this
+	v.Dx = factor * mag * math.Cos(theta)
+	v.Dy = factor * mag * math.Sin(theta)
+	return v
 }
 
-func (this Vector) Magnitude() float64 {
-	return math.Sqrt(math.Pow(this.Dx, 2.0) + math.Pow(this.Dy, 2.0))
+func (v Vector) Magnitude() float64 {
+	return math.Sqrt(math.Pow(v.Dx, 2.0) + math.Pow(v.Dy, 2.0))
 }
 
-func (this Vector) GetPolarAngle() float64 {
-	return math.Atan2(this.Dy, this.Dx)
+func (v Vector) GetPolarAngle() float64 {
+	return math.Atan2(v.Dy, v.Dx)
 }