mirror of
https://github.com/xiaoqidun/ofdgo.git
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76 lines
2.6 KiB
Go
76 lines
2.6 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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// 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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