embedded font in svg (#292)

formatters/api.go

@@ -21,7 +21,7 @@ var (
 	}))
 	// Default HTML formatter outputs self-contained HTML.
 	htmlFull = Register("html", html.New(html.Standalone(), html.WithClasses())) // nolint
-	Svg      = Register("svg", svg.New())
+	SVG      = Register("svg", svg.New(svg.EmbedFont("Liberation Mono", svg.FontLiberationMono, svg.WOFF)))
 )
 
 // Fallback formatter.

formatters/svg/svg.go

@@ -2,8 +2,12 @@
 package svg
 
 import (
+	"encoding/base64"
+	"errors"
 	"fmt"
 	"io"
+	"io/ioutil"
+	"path"
 	"strings"
 
 	"github.com/alecthomas/chroma"
@@ -12,9 +16,38 @@ import (
 // Option sets an option of the SVG formatter.
 type Option func(f *Formatter)
 
+// FontFamily sets the font-family.
+func FontFamily(fontFamily string) Option { return func(f *Formatter) { f.fontFamily = fontFamily } }
+
+// EmbedFontFile embeds given font file
+func EmbedFontFile(fontFamily string, fileName string) (option Option, err error) {
+	var format FontFormat
+	switch path.Ext(fileName) {
+	case ".woff":
+		format = WOFF
+	case ".woff2":
+		format = WOFF2
+	case ".ttf":
+		format = TRUETYPE
+	default:
+		return nil, errors.New("unexpected font file suffix")
+	}
+
+	var content []byte
+	if content, err = ioutil.ReadFile(fileName); err == nil {
+		option = EmbedFont(fontFamily, base64.StdEncoding.EncodeToString(content), format)
+	}
+	return
+}
+
+// EmbedFont embeds given base64 encoded font
+func EmbedFont(fontFamily string, font string, format FontFormat) Option {
+	return func(f *Formatter) { f.fontFamily = fontFamily; f.embeddedFont = font; f.fontFormat = format }
+}
+
 // New SVG formatter.
 func New(options ...Option) *Formatter {
-	f := &Formatter{}
+	f := &Formatter{fontFamily: "Consolas, Monaco, Lucida Console, Liberation Mono, DejaVu Sans Mono, Bitstream Vera Sans Mono, Courier New, monospace"}
 	for _, option := range options {
 		option(f)
 	}
@@ -23,6 +56,9 @@ func New(options ...Option) *Formatter {
 
 // Formatter that generates SVG.
 type Formatter struct {
+	fontFamily   string
+	embeddedFont string
+	fontFormat   FontFormat
 }
 
 func (f *Formatter) Format(w io.Writer, style *chroma.Style, iterator chroma.Iterator) (err error) {
@@ -56,8 +92,13 @@ func (f *Formatter) writeSVG(w io.Writer, style *chroma.Style, tokens []chroma.T
 	fmt.Fprint(w, "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n")
 	fmt.Fprint(w, "<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.0//EN\" \"http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd\">\n")
 	fmt.Fprintf(w, "<svg height=\"%d\" xmlns=\"http://www.w3.org/2000/svg\">\n", len(lines)*22)
+
+	if f.embeddedFont != "" {
+		f.writeFontStyle(w)
+	}
+
 	fmt.Fprintf(w, "<rect width=\"100%%\" height=\"100%%\" fill=\"%s\"/>\n", style.Get(chroma.Background).Background.String())
-	fmt.Fprintf(w, "<g font-family=\"Consolas, Monaco, Lucida Console, Liberation Mono, DejaVu Sans Mono, Bitstream Vera Sans Mono, Courier New, monospace\" font-size=\"14px\" fill=\"%s\">\n", style.Get(chroma.Text).Colour.String())
+	fmt.Fprintf(w, "<g font-family=\"%s\" font-size=\"14px\" fill=\"%s\">\n", f.fontFamily, style.Get(chroma.Text).Colour.String())
 
 	f.writeTokenBackgrounds(w, lines, style)
 
@@ -96,6 +137,32 @@ func (f *Formatter) writeTokenBackgrounds(w io.Writer, lines [][]chroma.Token, s
 	}
 }
 
+type FontFormat int
+
+// https://transfonter.org/formats
+const (
+	WOFF FontFormat = iota
+	WOFF2
+	TRUETYPE
+)
+
+var fontFormats = [...]string{
+	"woff",
+	"woff2",
+	"truetype",
+}
+
+func (f *Formatter) writeFontStyle(w io.Writer) {
+	fmt.Fprintf(w, `<style>
+@font-face {
+	font-family: '%s';
+	src: url(data:application/x-font-%s;charset=utf-8;base64,%s) format('%s');'
+	font-weight: normal;
+	font-style: normal;
+}
+</style>`, f.fontFamily, fontFormats[f.fontFormat], f.embeddedFont, fontFormats[f.fontFormat])
+}
+
 func (f *Formatter) styleAttr(styles map[chroma.TokenType]string, tt chroma.TokenType) string {
 	if _, ok := styles[tt]; !ok {
 		tt = tt.SubCategory()