🐛 Recognize variable font named instances #18400

Author: 88250

kernel/util/font.go

@@ -17,6 +17,7 @@
 package util
 
 import (
+	"encoding/binary"
 	"errors"
 	"os"
 	"sort"
@@ -74,8 +75,7 @@ func loadFonts() (ret []*Font) {
 				//LogInfof("[%s] [%s]", fontPath, family)
 			}
 		} else if strings.HasSuffix(strings.ToLower(fontPath), ".otf") || strings.HasSuffix(strings.ToLower(fontPath), ".ttf") {
-			f := parseTTFFontFamily(fontPath)
-			if nil != f {
+			for _, f := range parseTTFFontFamily(fontPath) {
 				if existFont(f, ret) {
 					continue
 				}
@@ -114,15 +114,12 @@ func parseTTCFontFamily(fontPath string) (ret []*Font) {
 	}
 
 	for _, f := range fonts {
-		font := parseFont(f)
-		if nil != font {
-			ret = append(ret, font)
-		}
+		ret = append(ret, parseFont(f)...)
 	}
 	return
 }
 
-func parseTTFFontFamily(fontPath string) *Font {
+func parseTTFFontFamily(fontPath string) (ret []*Font) {
 	defer logging.Recover()
 
 	fontFile, err := os.Open(fontPath)
@@ -140,9 +137,76 @@ func parseTTFFontFamily(fontPath string) *Font {
 	return parseFont(font)
 }
 
-func parseFont(font *sfnt.Font) *Font {
-	ret, _ := parseFontInfo(font)
-	return ret
+func parseFont(font *sfnt.Font) (ret []*Font) {
+	defaultFont, err := parseFontInfo(font)
+	if err != nil {
+		return nil
+	}
+	ret = append(ret, defaultFont)
+	ret = append(ret, parseFontVariations(font, defaultFont.Family)...)
+	return
+}
+
+func parseFontVariations(font *sfnt.Font, family string) (ret []*Font) {
+	defer logging.Recover()
+
+	// 可变字体通过 fvar 表声明字重等可变轴，named instances 提供了命名的字重实例
+	table, err := font.Table(sfnt.MustNamedTag("fvar"))
+	if err != nil {
+		return nil
+	}
+	buf := table.Bytes()
+	if len(buf) < 16 {
+		return nil
+	}
+	axesArrayOffset := int(binary.BigEndian.Uint16(buf[4:6]))
+	axisCount := int(binary.BigEndian.Uint16(buf[8:10]))
+	axisSize := int(binary.BigEndian.Uint16(buf[10:12]))
+	instanceCount := int(binary.BigEndian.Uint16(buf[12:14]))
+	instanceSize := int(binary.BigEndian.Uint16(buf[14:16]))
+	if axisSize < 20 || instanceSize < 4+axisCount*4 || len(buf) < axesArrayOffset+axisCount*axisSize+instanceCount*instanceSize {
+		return nil
+	}
+
+	// 找到 wght 轴在实例坐标中的位置
+	wghtAxisIndex := -1
+	for i := 0; i < axisCount; i++ {
+		base := axesArrayOffset + i*axisSize
+		if "wght" == string(buf[base:base+4]) {
+			wghtAxisIndex = i
+			break
+		}
+	}
+	if wghtAxisIndex < 0 {
+		return nil
+	}
+
+	t, err := font.NameTable()
+	if err != nil {
+		return nil
+	}
+	entries := t.List()
+	instancesBase := axesArrayOffset + axisCount*axisSize
+	for i := 0; i < instanceCount; i++ {
+		base := instancesBase + i*instanceSize
+		subfamilyNameID := binary.BigEndian.Uint16(buf[base : base+2])
+		// wght 坐标是 16.16 定点数，取整后即为 CSS font-weight
+		weight := int(float64(int32(binary.BigEndian.Uint32(buf[base+4+wghtAxisIndex*4:base+8+wghtAxisIndex*4])))/65536 + 0.5)
+		if weight < 1 || 1000 < weight {
+			continue
+		}
+		subfamily := selectFontName(entries, sfnt.NameID(subfamilyNameID))
+		if "" == subfamily {
+			continue
+		}
+
+		displayName := family
+		if !strings.EqualFold(subfamily, "Regular") {
+			displayName = family + " " + subfamily
+		}
+		ret = append(ret, &Font{Family: family, Weight: weight, DisplayName: displayName})
+	}
+	return
 }
 
 func parseFontInfo(font *sfnt.Font) (*Font, error) {