mirror of
https://github.com/xiaoqidun/ofdgo.git
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129 lines
4.3 KiB
Go
129 lines
4.3 KiB
Go
// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package ofdgo
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import "fmt"
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// FontMetrics 提供不依赖绘图库的字体度量，所有整数尺寸使用字体设计单位
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// VerticalMetrics依次返回非负的上升高度、下降高度和行间隙
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// Write返回独立的SFNT数据，调用方不得修改字体实例
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type FontMetrics interface {
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UnitsPerEm() uint16
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NumGlyphs() uint16
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GlyphIndex(rune) uint16
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GlyphAdvance(uint16) uint16
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VerticalMetrics() (uint16, uint16, uint16)
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Write() []byte
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}
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// ResolvedFont 保存字体来源和只读字体数据，不将外部字体写入文档
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type ResolvedFont struct {
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Data []byte
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Source string
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Face *FontFace
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Exact bool
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}
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// FontBackend 统一字体来源与度量，exact禁止使用无关回退字体
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// ResolveFont不得递归调用Renderer.ResolveFont，OpenFont不得修改输入数据
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type FontBackend interface {
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Backend
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ResolveFont(renderer *Renderer, id string, exact bool) (ResolvedFont, error)
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OpenFont(data []byte) (FontMetrics, error)
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}
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// resolvedFontKey 区分只读资源的字体标识与精确匹配要求
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type resolvedFontKey struct {
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id string
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exact bool
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definition *Font
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}
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// resolvedFontResult 缓存字体解析结果及不可用原因
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type resolvedFontResult struct {
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font ResolvedFont
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err error
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}
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// resetFontCache 重置字体解析及后端私有缓存，不预先创建任何绘图库对象
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func (r *Renderer) resetFontCache() {
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r.preparedFonts = make(map[string]*PreparedFont)
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r.resolvedFonts = make(map[resolvedFontKey]resolvedFontResult)
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r.backendStates = make(map[any]any)
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}
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// ResolveFont 使用配置的字体后端解析资源，保留精确匹配与回退的区别
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// 入参: id 字体资源标识, exact 是否要求精确匹配
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// 返回: ResolvedFont 字体与来源, error 解析错误
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func (r *Renderer) ResolveFont(id string, exact bool) (ResolvedFont, error) {
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if r.backends.Fonts == nil {
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return ResolvedFont{}, fmt.Errorf("fonts: %w", ErrBackendUnavailable)
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}
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key := resolvedFontKey{id: id, exact: exact, definition: r.Reader.fontCache[id]}
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if cached, ok := r.resolvedFonts[key]; ok {
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return cached.font, cached.err
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}
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resolved, err := r.backends.Fonts.ResolveFont(r, id, exact)
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key.definition = r.Reader.fontCache[id]
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r.resolvedFonts[key] = resolvedFontResult{font: resolved, err: err}
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return resolved, err
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}
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// PreparedFont 保存绘制用字体及GID、CID到包装字符的映射，所有数据只读
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// Data可与源编码不同，原始资源仍由ResolveFont和Reader保留
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type PreparedFont struct {
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ResolvedFont
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Glyphs map[uint16]rune
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CIDs map[uint16]rune
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}
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// PrepareFont 统一处理内嵌字体包装和索引映射，供各编译器复用
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// 入参: id 字体资源标识
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// 返回: *PreparedFont 绘制字体, error 字体解析错误
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func (r *Renderer) PrepareFont(id string) (*PreparedFont, error) {
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if cached := r.preparedFonts[id]; cached != nil {
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return cached, nil
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}
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resolved, err := r.ResolveFont(id, false)
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if err != nil {
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return nil, err
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}
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prepared := &PreparedFont{ResolvedFont: resolved}
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definition := r.Reader.fontCache[id]
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if definition != nil && definition.FontFile != "" {
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prepared.CIDs = getCFFCIDRuneMap(resolved.Data)
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if _, data, mapping, _, err := FixFontDataAggressive(resolved.Data, true, true); err == nil {
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prepared.Data = data
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if mapping != nil {
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prepared.Glyphs = make(map[uint16]rune)
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for character, glyph := range mapping {
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if character == packedGlyphRune(glyph) {
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prepared.Glyphs[glyph] = character
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}
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}
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for character, glyph := range mapping {
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if _, ok := prepared.Glyphs[glyph]; !ok {
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prepared.Glyphs[glyph] = character
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}
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}
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}
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}
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}
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if definition != nil {
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r.preparedFonts[id] = prepared
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}
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return prepared, nil
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}
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