Support for highlighting ranges of lines.

cmd/chroma/main.go

@@ -40,8 +40,9 @@ var (
 	htmlInlineStyleFlag    = kingpin.Flag("html-inline-styles", "Output HTML with inline styles (no classes).").Bool()
 	htmlTabWidthFlag       = kingpin.Flag("html-tab-width", "Set the HTML tab width.").Default("8").Int()
 	htmlLinesFlag          = kingpin.Flag("html-line-numbers", "Include line numbers in output.").Bool()
-	htmlHighlightStyleFlag = kingpin.Flag("html-highlight-style", "Style used for highlighting lines.").Default("bg:#yellow").String()
-	htmlHighlightFlag      = kingpin.Flag("html-highlight", "Highlight these ranges (N:M).").Strings()
+	htmlLinesStyleFlag     = kingpin.Flag("html-line-numbers-style", "Style for line numbers.").Default("#888").String()
+	htmlHighlightFlag      = kingpin.Flag("html-highlight", "Highlight these lines.").PlaceHolder("N[:M][,...]").String()
+	htmlHighlightStyleFlag = kingpin.Flag("html-highlight-style", "Style used for highlighting lines.").Default("bg:#282828").String()
 
 	filesArgs = kingpin.Arg("files", "Files to highlight.").ExistingFiles()
 )
@@ -94,6 +95,16 @@ command, for Go.
 	if *htmlFlag {
 		*formatterFlag = "html"
 	}
+
+	// Retrieve user-specified style, clone it, and add some overrides.
+	style := styles.Get(*styleFlag).Clone()
+	if *htmlHighlightStyleFlag != "" {
+		style.Add(chroma.LineHighlight, *htmlHighlightStyleFlag)
+	}
+	if *htmlLinesStyleFlag != "" {
+		style.Add(chroma.LineNumbers, *htmlLinesStyleFlag)
+	}
+
 	if *formatterFlag == "html" {
 		options := []html.Option{html.TabWidth(*htmlTabWidthFlag)}
 		if *htmlPrefixFlag != "" {
@@ -103,7 +114,7 @@ command, for Go.
 		// Dump styles.
 		if *htmlStylesFlag {
 			formatter := html.New(html.WithClasses())
-			formatter.WriteCSS(w, styles.Get(*styleFlag))
+			formatter.WriteCSS(w, style)
 			return
 		}
 		if !*htmlInlineStyleFlag {
@@ -117,22 +128,25 @@ command, for Go.
 		}
 		if len(*htmlHighlightFlag) > 0 {
 			ranges := [][2]int{}
-			for _, span := range *htmlHighlightFlag {
+			for _, span := range strings.Split(*htmlHighlightFlag, ",") {
 				parts := strings.Split(span, ":")
-				if len(parts) != 2 {
-					kingpin.Fatalf("range should be N:M, not %q", span)
+				if len(parts) > 2 {
+					kingpin.Fatalf("range should be N[:M], not %q", span)
 				}
 				start, err := strconv.ParseInt(parts[0], 10, 64)
 				kingpin.FatalIfError(err, "min value of range should be integer not %q", parts[0])
-				end, err := strconv.ParseInt(parts[0], 10, 64)
-				kingpin.FatalIfError(err, "max value of range should be integer not %q", parts[0])
+				end := start
+				if len(parts) == 2 {
+					end, err = strconv.ParseInt(parts[1], 10, 64)
+					kingpin.FatalIfError(err, "max value of range should be integer not %q", parts[1])
+				}
 				ranges = append(ranges, [2]int{int(start), int(end)})
 			}
-			options = append(options, html.HighlightLines(*htmlHighlightStyleFlag, ranges))
+			options = append(options, html.HighlightLines(ranges))
 		}
 		formatters.Register("html", html.New(options...))
 	}
-	writer := getWriter(w)
+	writer := getWriter(w, style)
 	if len(*filesArgs) == 0 {
 		contents, err := ioutil.ReadAll(os.Stdin)
 		kingpin.FatalIfError(err, "")
@@ -201,8 +215,7 @@ func selexer(path, contents string) (lexer chroma.Lexer) {
 	return lexers.Analyse(contents)
 }
 
-func getWriter(w io.Writer) func(*chroma.Token) {
-	style := styles.Get(*styleFlag)
+func getWriter(w io.Writer, style *chroma.Style) func(*chroma.Token) {
 	formatter := formatters.Get(*formatterFlag)
 	// formatter := formatters.TTY8
 	writer, err := formatter.Format(w, style)

formatters/html/html.go

@@ -32,12 +32,11 @@ func WithLineNumbers() Option {
 	}
 }
 
-// HighlightLines higlights the given line ranges.
+// HighlightLines higlights the given line ranges with the Highlight style.
 //
 // A range is the beginning and ending of a range as 1-based line numbers, inclusive.
-func HighlightLines(style string, ranges [][2]int) Option {
+func HighlightLines(ranges [][2]int) Option {
 	return func(f *Formatter) {
-		f.highlightStyle = style
 		f.highlightRanges = ranges
 		sort.Sort(f.highlightRanges)
 	}
@@ -59,7 +58,6 @@ type Formatter struct {
 	classes         bool
 	tabWidth        int
 	lineNumbers     bool
-	highlightStyle  string
 	highlightRanges highlightRanges
 }
 
@@ -104,7 +102,21 @@ func (f *Formatter) writeHTML(w io.Writer, style *chroma.Style, tokens []*chroma
 	fmt.Fprintf(w, "<pre%s>\n", f.styleAttr(css, chroma.Background))
 	lines := splitTokensIntoLines(tokens)
 	lineDigits := len(fmt.Sprintf("%d", len(lines)))
+	highlightIndex := 0
 	for line, tokens := range lines {
+		highlight := false
+		for highlightIndex < len(f.highlightRanges) && line+1 > f.highlightRanges[highlightIndex][1] {
+			highlightIndex++
+		}
+		if highlightIndex < len(f.highlightRanges) {
+			hrange := f.highlightRanges[highlightIndex]
+			if line+1 >= hrange[0] && line+1 <= hrange[1] {
+				highlight = true
+			}
+		}
+		if highlight {
+			fmt.Fprintf(w, "<span class=\"hl\">")
+		}
 		if f.lineNumbers {
 			fmt.Fprintf(w, "<span class=\"ln\">%*d</span>", lineDigits, line+1)
 		}
@@ -117,6 +129,9 @@ func (f *Formatter) writeHTML(w io.Writer, style *chroma.Style, tokens []*chroma
 			}
 			fmt.Fprint(w, html)
 		}
+		if highlight {
+			fmt.Fprintf(w, "</span>")
+		}
 	}
 
 	fmt.Fprint(w, "</pre>\n")
@@ -134,7 +149,7 @@ func (f *Formatter) class(tt chroma.TokenType) string {
 		return "chroma"
 	case chroma.LineNumbers:
 		return "ln"
-	case chroma.Highlight:
+	case chroma.LineHighlight:
 		return "hl"
 	}
 	if tt < 0 {
@@ -173,11 +188,6 @@ func (f *Formatter) WriteCSS(w io.Writer, style *chroma.Style) error {
 	if _, err := fmt.Fprintf(w, "/* %s */ .chroma { %s }\n", chroma.Background, css[chroma.Background]); err != nil {
 		return err
 	}
-	// No line-numbers, add a default.
-	if _, ok := css[chroma.LineNumbers]; !ok {
-		css[chroma.LineNumbers] = "color: #888"
-	}
-	css[chroma.LineNumbers] += "; margin-right: 0.5em"
 	tts := []int{}
 	for tt := range css {
 		tts = append(tts, int(tt))
@@ -199,11 +209,6 @@ func (f *Formatter) WriteCSS(w io.Writer, style *chroma.Style) error {
 func (f *Formatter) styleToCSS(style *chroma.Style) map[chroma.TokenType]string {
 	bg := style.Get(chroma.Background)
 	classes := map[chroma.TokenType]string{}
-	// Insert highlight colour if needed.
-	if len(f.highlightRanges) > 0 {
-		highlight := chroma.ParseStyleEntry(bg, f.highlightStyle).Sub(bg)
-		classes[chroma.Highlight] = StyleEntryToCSS(highlight)
-	}
 	// Convert the style.
 	for t := range style.Entries {
 		e := style.Entries[t]
@@ -213,6 +218,8 @@ func (f *Formatter) styleToCSS(style *chroma.Style) map[chroma.TokenType]string
 		classes[t] = StyleEntryToCSS(e)
 	}
 	classes[chroma.Background] += f.tabWidthStyle()
+	classes[chroma.LineNumbers] += "; margin-right: 0.5em"
+	classes[chroma.LineHighlight] += "; display: block; width: 100%"
 	return classes
 }
 

style.go

@@ -17,6 +17,13 @@ type StyleEntry struct {
 	Underline bool
 }
 
+// Clone this StyleEntry.
+func (s *StyleEntry) Clone() *StyleEntry {
+	clone := &StyleEntry{}
+	*clone = *s
+	return clone
+}
+
 func (s *StyleEntry) String() string {
 	out := []string{}
 	if s.Bold {
@@ -89,6 +96,18 @@ type Style struct {
 	Entries map[TokenType]*StyleEntry
 }
 
+// Clone this style. The clone can then be safely modified.
+func (s *Style) Clone() *Style {
+	clone := &Style{
+		Name:    s.Name,
+		Entries: map[TokenType]*StyleEntry{},
+	}
+	for tt, e := range s.Entries {
+		clone.Entries[tt] = e.Clone()
+	}
+	return clone
+}
+
 // Get a style entry. Will try sub-category or category if an exact match is not found, and
 // finally return the entry mapped to `InheritStyle`.
 func (s *Style) Get(ttype TokenType) *StyleEntry {