fix: correct SVG @font-face CSS syntax and MIME types

alecthomas · claude · alecthomas · commit 7eff9566790e · 2026-07-05T15:55:18.000+10:00
A stray trailing apostrophe after the src declaration made the
embedded-font CSS invalid, and the data URI used the obsolete
application/x-font-* MIME types. fontFormats now pairs each
format's modern MIME type (font/woff, font/woff2, font/ttf) with
its CSS format() hint, which differ for TrueType.

Co-Authored-By: Claude Fable 5 &lt;noreply@anthropic.com&gt;
diff --git a/formatters/svg/svg.go b/formatters/svg/svg.go
@@ -157,21 +157,22 @@ const (
 	TRUETYPE
 )
 
-var fontFormats = [...]string{
-	"woff",
-	"woff2",
-	"truetype",
+// The CSS format() hint differs from the MIME type for TrueType.
+var fontFormats = [...]struct{ mime, format string }{
+	{"font/woff", "woff"},
+	{"font/woff2", "woff2"},
+	{"font/ttf", "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');'
+	src: url(data:%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])
+</style>`, f.fontFamily, fontFormats[f.fontFormat].mime, f.embeddedFont, fontFormats[f.fontFormat].format)
 }
 
 func (f *Formatter) styleAttr(styles map[chroma.TokenType]string, tt chroma.TokenType) string {
diff --git a/formatters/svg/svg_test.go b/formatters/svg/svg_test.go
@@ -0,0 +1,28 @@
+package svg
+
+import (
+	"strings"
+	"testing"
+
+	assert "github.com/alecthomas/assert/v2"
+)
+
+func TestWriteFontStyle(t *testing.T) {
+	tests := []struct {
+		name     string
+		format   FontFormat
+		expected string
+	}{
+		{"WOFF", WOFF, "src: url(data:font/woff;charset=utf-8;base64,AAAA) format('woff');\n"},
+		{"WOFF2", WOFF2, "src: url(data:font/woff2;charset=utf-8;base64,AAAA) format('woff2');\n"},
+		{"TrueType", TRUETYPE, "src: url(data:font/ttf;charset=utf-8;base64,AAAA) format('truetype');\n"},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			f := New(EmbedFont("Test", "AAAA", test.format))
+			w := &strings.Builder{}
+			f.writeFontStyle(w)
+			assert.Contains(t, w.String(), test.expected)
+		})
+	}
+}
