fix: resolves #498

Resolves an issue whereby background colors were written to the terminal
output when colorization was applied.

vendor/github.com/alecthomas/chroma/formatters/svg/svg.go

@@ -0,0 +1,222 @@
+// Package svg contains an SVG formatter.
+package svg
+
+import (
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"path"
+	"strings"
+
+	"github.com/alecthomas/chroma"
+)
+
+// 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{fontFamily: "Consolas, Monaco, Lucida Console, Liberation Mono, DejaVu Sans Mono, Bitstream Vera Sans Mono, Courier New, monospace"}
+	for _, option := range options {
+		option(f)
+	}
+	return f
+}
+
+// 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) {
+	f.writeSVG(w, style, iterator.Tokens())
+	return err
+}
+
+var svgEscaper = strings.NewReplacer(
+	`&`, "&",
+	`<`, "&lt;",
+	`>`, "&gt;",
+	`"`, "&quot;",
+	` `, "&#160;",
+	`	`, "&#160;&#160;&#160;&#160;",
+)
+
+// EscapeString escapes special characters.
+func escapeString(s string) string {
+	return svgEscaper.Replace(s)
+}
+
+func (f *Formatter) writeSVG(w io.Writer, style *chroma.Style, tokens []chroma.Token) { // nolint: gocyclo
+	svgStyles := f.styleToSVG(style)
+	lines := chroma.SplitTokensIntoLines(tokens)
+
+	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 width=\"%dpx\" height=\"%dpx\" xmlns=\"http://www.w3.org/2000/svg\">\n", 8*maxLineWidth(lines), 10+int(16.8*float64(len(lines)+1)))
+
+	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=\"%s\" font-size=\"14px\" fill=\"%s\">\n", f.fontFamily, style.Get(chroma.Text).Colour.String())
+
+	f.writeTokenBackgrounds(w, lines, style)
+
+	for index, tokens := range lines {
+		fmt.Fprintf(w, "<text x=\"0\" y=\"%fem\" xml:space=\"preserve\">", 1.2*float64(index+1))
+
+		for _, token := range tokens {
+			text := escapeString(token.String())
+			attr := f.styleAttr(svgStyles, token.Type)
+			if attr != "" {
+				text = fmt.Sprintf("<tspan %s>%s</tspan>", attr, text)
+			}
+			fmt.Fprint(w, text)
+		}
+		fmt.Fprint(w, "</text>")
+	}
+
+	fmt.Fprint(w, "\n</g>\n")
+	fmt.Fprint(w, "</svg>\n")
+}
+
+func maxLineWidth(lines [][]chroma.Token) int {
+	maxWidth := 0
+	for _, tokens := range lines {
+		length := 0
+		for _, token := range tokens {
+			length += len(strings.Replace(token.String(), `	`, "    ", -1))
+		}
+		if length > maxWidth {
+			maxWidth = length
+		}
+	}
+	return maxWidth
+}
+
+// There is no background attribute for text in SVG so simply calculate the position and text
+// of tokens with a background color that differs from the default and add a rectangle for each before
+// adding the token.
+func (f *Formatter) writeTokenBackgrounds(w io.Writer, lines [][]chroma.Token, style *chroma.Style) {
+	for index, tokens := range lines {
+		lineLength := 0
+		for _, token := range tokens {
+			length := len(strings.Replace(token.String(), `	`, "    ", -1))
+			tokenBackground := style.Get(token.Type).Background
+			if tokenBackground.IsSet() && tokenBackground != style.Get(chroma.Background).Background {
+				fmt.Fprintf(w, "<rect id=\"%s\" x=\"%dch\" y=\"%fem\" width=\"%dch\" height=\"1.2em\" fill=\"%s\" />\n", escapeString(token.String()), lineLength, 1.2*float64(index)+0.25, length, style.Get(token.Type).Background.String())
+			}
+			lineLength += length
+		}
+	}
+}
+
+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()
+		if _, ok := styles[tt]; !ok {
+			tt = tt.Category()
+			if _, ok := styles[tt]; !ok {
+				return ""
+			}
+		}
+	}
+	return styles[tt]
+}
+
+func (f *Formatter) styleToSVG(style *chroma.Style) map[chroma.TokenType]string {
+	converted := map[chroma.TokenType]string{}
+	bg := style.Get(chroma.Background)
+	// Convert the style.
+	for t := range chroma.StandardTypes {
+		entry := style.Get(t)
+		if t != chroma.Background {
+			entry = entry.Sub(bg)
+		}
+		if entry.IsZero() {
+			continue
+		}
+		converted[t] = StyleEntryToSVG(entry)
+	}
+	return converted
+}
+
+// StyleEntryToSVG converts a chroma.StyleEntry to SVG attributes.
+func StyleEntryToSVG(e chroma.StyleEntry) string {
+	var styles []string
+
+	if e.Colour.IsSet() {
+		styles = append(styles, "fill=\""+e.Colour.String()+"\"")
+	}
+	if e.Bold == chroma.Yes {
+		styles = append(styles, "font-weight=\"bold\"")
+	}
+	if e.Italic == chroma.Yes {
+		styles = append(styles, "font-style=\"italic\"")
+	}
+	if e.Underline == chroma.Yes {
+		styles = append(styles, "text-decoration=\"underline\"")
+	}
+	return strings.Join(styles, " ")
+}