Add SetDashPattern() method

3 files changed, 54 insertions, 0 deletions

diff --git a/def.go b/def.go
index 47b399f..df21e05 100644
--- a/def.go
+++ b/def.go
@@ -195,6 +195,8 @@ type Fpdf struct {
 	fontDirStr       string                    // location of font definition files
 	capStyle         int                       // line cap style: butt 0, round 1, square 2
 	joinStyle        int                       // line segment join style: miter 0, round 1, bevel 2
+	dashArray        []float64                 // dash array
+	dashPhase        float64                   // dash phase
 	blendList        []blendModeType           // slice[idx] of alpha transparency modes, 1-based
 	blendMap         map[string]int            // map into blendList
 	gradientList     []gradientType            // slice[idx] of gradient records
diff --git a/fpdf.go b/fpdf.go
index 3f6f511..1508548 100644
--- a/fpdf.go
+++ b/fpdf.go
@@ -36,6 +36,7 @@ import (
 	"math"
 	"os"
 	"path"
+	"strconv"
 	"strings"
 	"time"
 )
@@ -565,6 +566,10 @@ func (f *Fpdf) AddPageFormat(orientationStr string, size SizeType) {
 	// Set line width
 	f.lineWidth = lw
 	f.outf("%.2f w", lw*f.k)
+	// Set dash pattern
+	if len(f.dashArray) > 0 {
+		f.outputDashPattern()
+	}
 	// 	Set font
 	if familyStr != "" {
 		f.SetFont(familyStr, style, fontsize)
@@ -775,6 +780,40 @@ func (f *Fpdf) SetLineCapStyle(styleStr string) {
 	}
 }
 
+// SetDashPattern sets the dash pattern that is used to draw lines.
+// The dashArray elements are numbers that specify the lengths of alternating
+// dashes and gaps. The dash phase specifies the distance into the dash pattern
+// at which to start the dash. The dash pattern is retained from page to page.
+func (f *Fpdf) SetDashPattern(dashArray []float64, dashPhase float64) {
+	scaled := make([]float64, len(dashArray))
+	for i, value := range dashArray {
+		scaled[i] = value * f.k
+	}
+	dashPhase *= f.k
+	if !slicesEqual(scaled, f.dashArray) || dashPhase != f.dashPhase {
+		f.dashArray = scaled
+		f.dashPhase = dashPhase
+		if f.page > 0 {
+			f.outputDashPattern()
+		}
+	}
+}
+
+func (f *Fpdf) outputDashPattern() {
+	var buf bytes.Buffer
+	buf.WriteByte('[')
+	for i, value := range f.dashArray {
+		if i > 0 {
+			buf.WriteByte(' ')
+		}
+		buf.WriteString(strconv.FormatFloat(value, 'f', 2, 64))
+	}
+	buf.WriteString("] ")
+	buf.WriteString(strconv.FormatFloat(f.dashPhase, 'f', 2, 64))
+	buf.WriteString(" d")
+	f.outbuf(&buf)
+}
+
 // Line draws a line between points (x1, y1) and (x2, y2) using the current
 // draw color, line width and cap style.
 func (f *Fpdf) Line(x1, y1, x2, y2 float64) {
diff --git a/util.go b/util.go
index d3b114f..ed4ffdd 100644
--- a/util.go
+++ b/util.go
@@ -69,6 +69,19 @@ func bufferFromReader(r io.Reader) (b *bytes.Buffer, err error) {
 	return
 }
 
+// Returns true if the two specified integer slices are equal
+func slicesEqual(a, b []float64) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := range a {
+		if a[i] != b[i] {
+			return false
+		}
+	}
+	return true
+}
+
 // Returns a zlib-compressed copy of the specified byte array
 func sliceCompress(data []byte) []byte {
 	var buf bytes.Buffer