Use encoding/xml to encode svg

draw2dsvg/fileutil.go

@@ -2,18 +2,21 @@ package draw2dsvg
 
 import (
 	"os"
-	"bytes"
+	"encoding/xml"
 	_ "errors"
 )
 
-func SaveToSvgFile(filePath string, svg *SVG) error {
+func SaveToSvgFile(filePath string, svg *Svg) error {
 	f, err := os.Create(filePath)
 	if err != nil {
 		return err
 	}
 	defer f.Close()
 
-	bytes.NewBuffer((*bytes.Buffer)(svg).Bytes()).WriteTo(f) // clone buffer to make multiple writes possible
+	f.Write([]byte(xml.Header))
+	encoder := xml.NewEncoder(f)
+	encoder.Indent("", "\t")
+	err = encoder.Encode(svg)
 
-	return nil
+	return err
 }

draw2dsvg/gc.go

@@ -19,18 +19,18 @@ var (
 
 type SVG bytes.Buffer
 
-func NewSvg() *SVG {
-	return &SVG{}
+func NewSvg() *Svg {
+	return &Svg{Xmlns: "http://www.w3.org/2000/svg"}
 }
 
 // GraphicContext implements the draw2d.GraphicContext interface
 // It provides draw2d with a svg backend
 type GraphicContext struct {
 	*draw2dbase.StackGraphicContext
-	svg *SVG
+	svg *Svg
 }
 
-func NewGraphicContext(svg *SVG) *GraphicContext {
+func NewGraphicContext(svg *Svg) *GraphicContext {
 	gc := &GraphicContext{draw2dbase.NewStackGraphicContext(), svg}
 	return gc
 }

draw2dsvg/svg.go

@@ -0,0 +1,28 @@
+// Copyright 2015 The draw2d Authors. All rights reserved.
+// created: 16/12/2017 by Drahoslav Bednář
+package draw2dsvg
+
+import (
+	"encoding/xml"
+)
+
+type Svg struct {
+	XMLName xml.Name `xml:"svg"`
+	Xmlns string `xml:"xmlns,attr"`
+	Groups []Group `xml:"g"`
+}
+
+type Group struct {
+	Groups []Group `xml:"g"`
+	Paths []Path `xml:"path"`
+	Texts []Text `xml:"text"`
+}
+
+type Path struct {
+	Data string `xml:"d,attr"`
+}
+
+type Text struct {
+	Text string `xml:",innerxml"`
+	Style string `xml:",attr,omitempty"`
+}

draw2dsvg/xml_test.go

@@ -0,0 +1,57 @@
+// Copyright 2015 The draw2d Authors. All rights reserved.
+// created: 16/12/2017 by Drahoslav Bednář
+
+// Package draw2dsvg_test gives test coverage with the command:
+// go test -cover ./... | grep -v "no test"
+// (It should be run from its parent draw2d directory.)
+package draw2dsvg
+
+import (
+	"testing"
+	"encoding/xml"
+)
+
+// Test basic encoding of svg/xml elements
+func TestXml(t *testing.T) {
+	
+	svg := NewSvg()
+	svg.Groups = []Group{Group{
+		Groups: []Group{
+			Group{},  // nested groups
+			Group{},
+		},
+		Texts: []Text{
+			Text{Text: "Hello"}, // text
+			Text{Text: "world", Style: "opacity: 0.5"}, // text with style
+		},
+		Paths: []Path{
+			Path{Data: "M100,200 C100,100 250,100 250,200 S400,300 400,200"}, // simple path
+			Path{}, // empty path
+		},
+	}}
+
+	expectedOut := `<svg xmlns="http://www.w3.org/2000/svg">
+  <g>
+    <g></g>
+    <g></g>
+    <path d="M100,200 C100,100 250,100 250,200 S400,300 400,200"></path>
+    <path d=""></path>
+    <text>Hello</text>
+    <text Style="opacity: 0.5">world</text>
+  </g>
+</svg>`
+
+	out, err := xml.MarshalIndent(svg, "", "  ")
+
+	if err != nil {
+		t.Error(err)
+	}
+	if string(out) != expectedOut {
+		t.Errorf("svg output is not as expected\n"+
+			"got:\n%s\n\n"+
+			"want:\n%s\n",
+			string(out),
+			expectedOut,
+		)
+	}
+}