feat(字体处理): 优化字体压缩，降低裁剪开销

ofdgo_font_type2.go

@@ -55,6 +55,8 @@ type type2State struct {
 	seed             uint64
 	steps            *int
 	dependencies     map[uint16]bool
+	localUsage       []bool
+	globalUsage      []bool
 }
 
 // readType2Index 读取并校验CFF索引的全部偏移，不复制程序字节
@@ -336,13 +338,18 @@ func (s *type2State) run(data []byte, depth int) (bool, error) {
 			value := s.args[len(s.args)-1]
 			s.args = s.args[:len(s.args)-1]
 			subrs := s.font.locals
+			usage := s.localUsage
 			if op == 29 {
 				subrs = s.font.globals
+				usage = s.globalUsage
 			}
 			value += float64(cffSubrBias(len(subrs)))
 			if value < 0 || value >= float64(len(subrs)) || value != math.Trunc(value) {
 				return false, fmt.Errorf("invalid Type2 subroutine number")
 			}
+			if usage != nil {
+				usage[int(value)] = true
+			}
 			ended, err := s.run(subrs[int(value)], depth+1)
 			if ended || err != nil {
 				return ended, err
@@ -503,7 +510,7 @@ func (s *type2State) appendComponent(code, x, y float64) error {
 	if s.dependencies != nil {
 		s.dependencies[uint16(gid)] = true
 	}
-	child := type2State{font: s.font, matrix: s.matrix, width: s.font.def, component: true, output: s.output, originX: x, originY: y, outX: s.outX, outY: s.outY, seed: s.font.seed + uint64(gid), steps: s.steps, stripHints: s.stripHints, dependencies: s.dependencies}
+	child := type2State{font: s.font, matrix: s.matrix, width: s.font.def, component: true, output: s.output, originX: x, originY: y, outX: s.outX, outY: s.outY, seed: s.font.seed + uint64(gid), steps: s.steps, stripHints: s.stripHints, dependencies: s.dependencies, localUsage: s.localUsage, globalUsage: s.globalUsage}
 	_, err := child.run(s.font.chars[gid], 0)
 	if err != nil {
 		return fmt.Errorf("invalid Type2 component %s: %w", name, err)