[font] Tweak Cmap cache

font/font.go

@@ -620,8 +620,9 @@ func loadGDEF(ld *ot.Loader, axisCount int, gsub, gpos []byte) (tables.GDEF, err
 type Face struct {
 	*Font
 
-	extentsCache extentsCache
-	cmapCache    cache21_19_8
+	extentsCache          extentsCache
+	cmapCache             cache21_19_8 // supported runes, mapping to GID
+	cmapNotSupportedCache cache21_0_13 // not supported runes
 
 	coords       []tables.Coord
 	xPpem, yPpem uint16
@@ -631,6 +632,7 @@ type Face struct {
 func NewFace(font *Font) *Face {
 	out := &Face{Font: font, extentsCache: make(extentsCache, font.nGlyphs)}
 	out.cmapCache.clear()
+	out.cmapNotSupportedCache.clear()
 	return out
 }
 
@@ -639,12 +641,17 @@ func NewFace(font *Font) *Face {
 // Note that it only looks into the cmap, without taking account substitutions
 // nor variation selectors.
 func (f *Face) NominalGlyph(ch rune) (GID, bool) {
+	if notSupported := f.cmapNotSupportedCache.get(uint32(ch)); notSupported {
+		return 0, false
+	}
 	if g, ok := f.cmapCache.get(uint32(ch)); ok {
 		return GID(g), ok
 	}
 	g, ok := f.Cmap.Lookup(ch)
 	if ok {
 		f.cmapCache.set(uint32(ch), uint32(g))
+	} else {
+		f.cmapNotSupportedCache.set(uint32(ch))
 	}
 	return g, ok
 }

font/font_test.go

@@ -181,3 +181,35 @@ func TestBitmapExtents(t *testing.T) {
 	extents, ok := face.GlyphExtents(41)
 	tu.Assert(t, ok && extents.Width == 819.2 && extents.Height == -1433.6)
 }
+
+func BenchmarkCmap(b *testing.B) {
+	font := loadFont(b, "common/Roboto-BoldItalic.ttf")
+	face := NewFace(font)
+	latinText := []rune("Hi this is a test with some âccents : $£8")
+	chineseText := []rune("襄陽曲四首/魯中都東樓醉起作-李白 刊误")
+	mixedText := append(latinText, chineseText...)
+
+	b.ResetTimer()
+
+	b.Run("latin text", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			for _, r := range latinText {
+				_, _ = face.NominalGlyph(r)
+			}
+		}
+	})
+	b.Run("chinese text", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			for _, r := range chineseText {
+				_, _ = face.NominalGlyph(r)
+			}
+		}
+	})
+	b.Run("mixed text", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			for _, r := range mixedText {
+				_, _ = face.NominalGlyph(r)
+			}
+		}
+	})
+}

font/renderer_test.go

@@ -591,7 +591,8 @@ func TestAppleBitmapGlyph(t *testing.T) {
 	ft, err := NewFont(fonts[0])
 	tu.AssertNoErr(t, err)
 
-	face := Face{Font: ft, xPpem: 94, yPpem: 94}
+	face := NewFace(ft)
+	face.SetPpem(94, 94)
 
 	runes := "The quick brown fox jumps over the lazy dog"
 	for _, r := range runes {