feat(字体渲染): 优化字体解析与渲染缓存

ofdgo_font_sfnt.go

@@ -17,6 +17,7 @@ package ofdgo
 import (
 	"encoding/binary"
 	"fmt"
+	"maps"
 	"sort"
 	"sync"
 
@@ -47,11 +48,18 @@ func parseSFNTFont(data []byte) (*sfntFont, error) {
 	if err != nil {
 		return nil, err
 	}
+	return parseSFNTTables(table)
+}
+
+// parseSFNTTables 校验字体表并解析度量和字符映射，借用表数据且不修改其内容
+// 入参: table 字体表
+// 返回: *sfntFont 字体, error 格式错误
+func parseSFNTTables(table map[string][]byte) (*sfntFont, error) {
 	head, maxp, hhea := table["head"], table["maxp"], table["hhea"]
 	if len(head) != 54 || len(maxp) < 6 || len(hhea) < 36 {
 		return nil, fmt.Errorf("missing or truncated font metrics")
 	}
-	f := &sfntFont{Tables: table, IsTrueType: table["glyf"] != nil, IsCFF: table["CFF "] != nil}
+	f := &sfntFont{Tables: maps.Clone(table), IsTrueType: table["glyf"] != nil, IsCFF: table["CFF "] != nil}
 	f.units, f.count = binary.BigEndian.Uint16(head[18:]), binary.BigEndian.Uint16(maxp[4:])
 	f.horizontal = binary.BigEndian.Uint16(hhea[34:])
 	if f.units < 16 || f.units > 16384 || f.count == 0 || f.IsTrueType == f.IsCFF || !validSFNTMetrics(table["hmtx"], f.count, f.horizontal) {
@@ -72,10 +80,11 @@ func parseSFNTFont(data []byte) (*sfntFont, error) {
 			return nil, fmt.Errorf("invalid glyph location table")
 		}
 	}
-	f.cmaps, err = readSFNTCmaps(table["cmap"])
+	cmaps, err := readSFNTCmaps(table["cmap"])
 	if err != nil {
 		return nil, err
 	}
+	f.cmaps = cmaps
 	for _, cmap := range f.cmaps {
 		for _, glyph := range cmap.mapping {
 			if glyph >= f.count {

ofdgo_renderer_glyph_canvas.go

@@ -103,12 +103,24 @@ func (r *Renderer) cachedTextGlyphPath(face *canvas.FontFace, glyph textGlyph) (
 	}
 	outlines := r.canvasState().fontOutlines[face.Font]
 	if outlines == nil {
-		metrics, err := parseSFNTFont(fontSFNTData(face.Font.Tables))
-		if err != nil {
-			r.renderError = err
-			return &canvas.Path{}, 0
+		cache := r.canvasFontOutlines()
+		outlines, _ = cache.get(face.Font)
+		if outlines == nil {
+			metrics, err := parseSFNTTables(face.Font.Tables)
+			if err != nil {
+				r.renderError = err
+				return &canvas.Path{}, 0
+			}
+			outlines = &sfntOutliner{font: metrics}
+			cost := uint64(512)
+			for _, data := range metrics.Tables {
+				cost += uint64(len(data)) * 8
+			}
+			for _, cmap := range metrics.cmaps {
+				cost += uint64(len(cmap.mapping)) * 48
+			}
+			cache.put(face.Font, outlines, int(min(cost, uint64(cache.limit)+1)))
 		}
-		outlines = &sfntOutliner{font: metrics}
 		r.canvasState().fontOutlines[face.Font] = outlines
 	}
 	path, width, err := textGlyphPath(face, glyph, outlines)

ofdgo_renderer_state_canvas.go

@@ -36,6 +36,9 @@ type canvasPathCacheKey struct{}
 // canvasFillCacheKey 区分按填充规则规范化的共享路径缓存
 type canvasFillCacheKey struct{}
 
+// canvasOutlineCacheKey 区分子渲染器共享的字体轮廓解析缓存
+type canvasOutlineCacheKey struct{}
+
 // canvasFillKey 保存完整几何摘要及填充规则
 type canvasFillKey struct {
 	digest [32]byte
@@ -114,6 +117,18 @@ func (r *Renderer) canvasFontFamilies() *renderCache[canvasFontKey, *canvas.Font
 	return cache
 }
 
+// canvasFontOutlines 获取子渲染器共享的字体轮廓解析缓存，限制字体及解析数据保留量
+// 返回: *renderCache[*canvas.Font, *sfntOutliner] 字体轮廓缓存
+func (r *Renderer) canvasFontOutlines() *renderCache[*canvas.Font, *sfntOutliner] {
+	key := canvasOutlineCacheKey{}
+	if state, ok := r.sharedBackendStates[key]; ok {
+		return state.(*renderCache[*canvas.Font, *sfntOutliner])
+	}
+	cache := &renderCache[*canvas.Font, *sfntOutliner]{limit: 32 << 20}
+	r.sharedBackendStates[key] = cache
+	return cache
+}
+
 // canvasState 获取当前渲染器的Canvas私有缓存，按需创建且不向其他后端暴露
 // 返回: *canvasBackendState Canvas缓存
 func (r *Renderer) canvasState() *canvasBackendState {