feat(内存占用): 复用SVG字体资源，减少多页阅读的传输量和内存开销

assets/webui/ofdgo.js

@@ -53,6 +53,7 @@ const state = {
 	continuous: false,
 	renderAnnotations: true,
 	pageCache: new Map(),
+	svgFonts: new Map(),
 	selectedPages: new Set(),
 	pageInFlight: new Map(),
 	pageRenderQueue: [],
@@ -1509,6 +1510,10 @@ function renderPageFlow() {
 }
 
 function resetPageFlow() {
+	for (const font of state.svgFonts.values()) {
+		document.fonts.delete(font);
+	}
+	state.svgFonts.clear();
 	state.pageCache.clear();
 	state.selectedPages.clear();
 	state.visiblePages.clear();
@@ -1657,6 +1662,7 @@ async function processPageRenderQueue() {
 					continue;
 				}
 				const page = await callWASM("ofdgoRenderPage", task.index);
+				await loadSVGFonts(page.fonts, task.openSeq);
 				if (task.openSeq === state.openSeq) {
 					state.pageCache.set(task.index, page);
 				}
@@ -1672,6 +1678,28 @@ async function processPageRenderQueue() {
 	}
 }
 
+async function loadSVGFonts(fonts, openSeq) {
+	for (const font of fonts) {
+		if (openSeq !== state.openSeq) {
+			return;
+		}
+		if (state.svgFonts.has(font.name)) {
+			continue;
+		}
+		const data = await callWASM("ofdgoSVGFontData", font.name);
+		if (openSeq !== state.openSeq) {
+			return;
+		}
+		const face = new FontFace(font.name, data.bytes, { weight: String(font.weight), style: font.style });
+		await face.load();
+		if (openSeq !== state.openSeq) {
+			return;
+		}
+		document.fonts.add(face);
+		state.svgFonts.set(font.name, face);
+	}
+}
+
 function comparePageRenderTask(a, b) {
 	return a.priority - b.priority || Math.abs(a.index - state.pageIndex) - Math.abs(b.index - state.pageIndex);
 }

internal/webui/wasm.go

@@ -39,6 +39,7 @@ func RunWASM() {
 	registerCallback("ofdgoDocumentInfo", documentInfo)
 	registerCallback("ofdgoAttachmentData", attachmentData)
 	registerCallback("ofdgoRenderPage", renderPage)
+	registerCallback("ofdgoSVGFontData", svgFontData)
 	registerCallback("ofdgoSearchPage", searchPage)
 	registerCallback("ofdgoExportFormats", exportFormats)
 	registerCallback("ofdgoExportPage", exportPage)
@@ -150,6 +151,20 @@ func attachmentData(args []js.Value) (any, error) {
 	return successResult(map[string]any{"bytes": bytesToJS(data)}), nil
 }
 
+// svgFontData 读取SVG字体资源
+// 入参: args 浏览器参数
+// 返回: any 字体数据, error 错误信息
+func svgFontData(args []js.Value) (any, error) {
+	if currentSession == nil {
+		return nil, fmt.Errorf("ofd document is not opened")
+	}
+	data, err := currentSession.SVGFontData(args[0].String())
+	if err != nil {
+		return nil, err
+	}
+	return successResult(map[string]any{"bytes": bytesToJS(data)}), nil
+}
+
 // renderPage 渲染OFD页面
 // 入参: args 浏览器参数
 // 返回: any 页面SVG结果, error 错误信息
@@ -182,6 +197,10 @@ func renderPage(args []js.Value) (any, error) {
 			"height": link.Box.H,
 		}
 	}
+	fonts := make([]any, len(page.Fonts))
+	for i, font := range page.Fonts {
+		fonts[i] = map[string]any{"name": font.Name, "weight": font.Weight, "style": font.Style}
+	}
 	return successResult(map[string]any{
 		"index":  page.Index,
 		"number": page.Number,
@@ -190,6 +209,7 @@ func renderPage(args []js.Value) (any, error) {
 		"height": page.Height,
 		"svg":    page.SVG,
 		"links":  links,
+		"fonts":  fonts,
 		"text":   js.Global().Get("JSON").Call("parse", string(textData)),
 	}), nil
 }

internal/webui/webui.go

@@ -108,6 +108,7 @@ type Session struct {
 	pageCache      map[int]*ofdgo.PageContent
 	boxCache       map[int]ofdgo.Box
 	textCache      map[int]*ofdgo.PageText
+	svgFonts       map[string][]byte
 	signatures     []SignatureInfo
 	signatureError error
 	signaturesRead bool
@@ -165,6 +166,7 @@ type PageSVG struct {
 	Height float64          `json:"height"`
 	SVG    string           `json:"svg"`
 	Links  []ofdgo.PageLink `json:"-"`
+	Fonts  []ofdgo.SVGFont  `json:"-"`
 }
 
 // ExportFormat 导出格式
@@ -241,6 +243,7 @@ func Open(data []byte, opts OpenOptions) (*Session, error) {
 		pageCache: make(map[int]*ofdgo.PageContent),
 		boxCache:  make(map[int]ofdgo.Box),
 		textCache: make(map[int]*ofdgo.PageText),
+		svgFonts:  make(map[string][]byte),
 	}, nil
 }
 
@@ -267,6 +270,7 @@ func (s *Session) SetFonts(fonts []FontFile) error {
 		s.Renderer.SetFontFS()
 	}
 	clear(s.textCache)
+	clear(s.svgFonts)
 	return nil
 }
 
@@ -415,14 +419,30 @@ func (s *Session) RenderPageSVG(index int) (PageSVG, error) {
 		return PageSVG{}, err
 	}
 	var buf bytes.Buffer
-	if err := s.Renderer.RenderToSVG(page, &buf); err != nil {
+	fonts, err := s.Renderer.RenderToSVGWithFonts(page, &buf)
+	if err != nil {
 		return PageSVG{}, err
 	}
 	links, err := s.Renderer.PageLinks(page)
 	if err != nil {
 		return PageSVG{}, err
 	}
-	return PageSVG{Index: index, Number: index + 1, ID: pageRef.ID, Width: box.W, Height: box.H, SVG: buf.String(), Links: links}, nil
+	for i, font := range fonts {
+		s.svgFonts[font.Name] = font.Data
+		fonts[i].Data = nil
+	}
+	return PageSVG{Index: index, Number: index + 1, ID: pageRef.ID, Width: box.W, Height: box.H, SVG: buf.String(), Links: links, Fonts: fonts}, nil
+}
+
+// SVGFontData 获取已渲染页面引用的字体数据
+// 入参: name 字体资源标识
+// 返回: []byte 字体数据, error 错误信息
+func (s *Session) SVGFontData(name string) ([]byte, error) {
+	data, ok := s.svgFonts[name]
+	if !ok {
+		return nil, fmt.Errorf("svg font not found: %s", name)
+	}
+	return data, nil
 }
 
 // ExportPage 导出单页

ofdgo_renderer.go

@@ -35,6 +35,7 @@ type Renderer struct {
 	FontGIDMap            map[string]map[uint16]rune
 	FontCIDMap            map[string]map[uint16]rune
 	fontCache             map[fontCacheKey]*canvas.FontFamily
+	svgFontCache          map[*canvas.Font]SVGFont
 	fontSourceCache       map[string][]fontSource
 	fontSourceUsed        map[string]fontSource
 	fontDirCandidates     map[string][]fontFileCandidate
@@ -64,6 +65,7 @@ func (r *Renderer) resetFontCache() {
 	r.FontGIDMap = make(map[string]map[uint16]rune)
 	r.FontCIDMap = make(map[string]map[uint16]rune)
 	r.fontCache = make(map[fontCacheKey]*canvas.FontFamily)
+	r.svgFontCache = make(map[*canvas.Font]SVGFont)
 	r.fontSourceCache = make(map[string][]fontSource)
 	r.fontSourceUsed = make(map[string]fontSource)
 	r.fontDirCandidates = make(map[string][]fontFileCandidate)

ofdgo_renderer_svg.go

@@ -0,0 +1,93 @@
+// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ofdgo
+
+import (
+	"crypto/sha256"
+	"fmt"
+	"io"
+	"strings"
+
+	"github.com/tdewolff/canvas"
+	"github.com/tdewolff/canvas/renderers/svg"
+)
+
+// SVGFont SVG引用的字体资源，Name为CSS字体族标识，Data为只读字体数据
+type SVGFont struct {
+	Name   string
+	Weight int
+	Style  string
+	Data   []byte
+}
+
+// svgFontRenderer 分离字体资源的SVG渲染器
+type svgFontRenderer struct {
+	*svg.SVG
+	renderer *Renderer
+	fonts    []SVGFont
+	seen     map[string]bool
+	styles   strings.Builder
+}
+
+// RenderToSVGWithFonts 渲染为SVG并返回页面引用的字体资源，不在SVG中嵌入字体
+// 入参: page 页面内容, writer 输出流
+// 返回: []SVGFont 字体资源，可按Name复用并按Weight、Style注册，error 错误信息
+func (r *Renderer) RenderToSVGWithFonts(page *PageContent, writer io.Writer) ([]SVGFont, error) {
+	c, err := r.renderPage(page)
+	if err != nil {
+		return nil, err
+	}
+	options := svg.DefaultOptions
+	options.EmbedFonts = false
+	s := &svgFontRenderer{
+		SVG:      svg.New(writer, c.W, c.H, &options),
+		renderer: r,
+		seen:     make(map[string]bool),
+	}
+	c.RenderTo(s)
+	s.SetCustomStyle(s.styles.String())
+	return s.fonts, s.Close()
+}
+
+// RenderText 绘制文字并记录实际使用的字体资源
+// 入参: text 文字对象, m 变换矩阵
+func (s *svgFontRenderer) RenderText(text *canvas.Text, m canvas.Matrix) {
+	if text.Empty() {
+		return
+	}
+	font := text.MostCommonFontFace().Font
+	resource, ok := s.renderer.svgFontCache[font]
+	if !ok {
+		data := font.SFNT.Write()
+		resource = SVGFont{
+			Name:   fmt.Sprintf("ofdgo-%x-%d", sha256.Sum256(data), font.Style()),
+			Weight: font.Style().CSS(),
+			Style:  "normal",
+			Data:   data,
+		}
+		if font.Style().Italic() {
+			resource.Style = "italic"
+		}
+		s.renderer.svgFontCache[font] = resource
+	}
+	if !s.seen[resource.Name] {
+		s.seen[resource.Name] = true
+		s.fonts = append(s.fonts, resource)
+		fmt.Fprintf(&s.styles, ".%s{font-family:%s!important}", resource.Name, resource.Name)
+	}
+	s.SetClass(resource.Name)
+	s.SVG.RenderText(text, m)
+	s.SetClass()
+}