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// 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 (
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"fmt"
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"slices"
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"strconv"
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"strings"
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"github.com/go-text/typesetting/segmenter"
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)
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// layoutShapedText 将显式塑形结果保存为标准文字定位，成功前不修改对象
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// 入参: obj 文字对象, value 原文, options 排版选项, metrics 字体度量, width 行宽, lineHeight 行高, hScale 横向比例, baseline 首行基线
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// 返回: error 塑形或排版错误
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func layoutShapedText(obj *TextObject, value string, options TextLayout, metrics FontMetrics, width, lineHeight, hScale, baseline float64) error {
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shaper, ok := metrics.(FontShaper)
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if !ok {
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return fmt.Errorf("font shaping: %w", ErrBackendUnavailable)
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}
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var codes []TextCode
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var transforms []CGTransform
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offset := 0
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for _, paragraph := range strings.Split(value, "\n") {
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runes := []rune(paragraph)
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_, advances, err := shapeTextLine(shaper, runes, obj.Font, obj.Size, hScale, options.LetterSpacing)
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if err != nil {
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return err
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}
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lines := breakTextLines(runes, advances, width, options.Wrap, options.LetterSpacing, options.FirstLineIndent)
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for i := 0; i < len(lines); i++ {
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line := lines[i]
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indent := 0.0
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if i == 0 {
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indent = options.FirstLineIndent
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}
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available := width - indent
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glyphs, lineAdvances, err := shapeTextLine(shaper, runes[line[0]:line[1]], obj.Font, obj.Size, hScale, options.LetterSpacing)
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if err != nil {
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return err
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}
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for options.Wrap && shapedLineWidth(runes[line[0]:line[1]], lineAdvances, options.LetterSpacing) > available {
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var seg segmenter.Segmenter
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seg.Init(runes[line[0]:line[1]])
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previous := 0
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for it := seg.GraphemeIterator(); it.Next(); {
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previous = it.Grapheme().Offset
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}
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if previous == 0 {
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break
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}
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oldEnd := line[1]
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line[1] = line[0] + previous
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if i+1 < len(lines) {
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lines[i+1][0] = line[1]
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} else {
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lines = append(lines, [2]int{line[1], oldEnd})
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}
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lines[i] = line
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glyphs, lineAdvances, err = shapeTextLine(shaper, runes[line[0]:line[1]], obj.Font, obj.Size, hScale, options.LetterSpacing)
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if err != nil {
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return err
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}
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}
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chars := runes[line[0]:line[1]]
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x, delta := alignTextLine(chars, lineAdvances, available, options.Align, i+1 < len(lines), options.LetterSpacing)
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x += options.LeftIndent + indent
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y := baseline + float64(len(codes))*lineHeight
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if !finite(x) || !finite(y) {
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return fmt.Errorf("text position exceeds finite range")
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}
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adjusted := parseFloats(delta)
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extra := make([]float64, len(chars)+1)
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raw := make([]float64, len(chars))
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for _, glyph := range glyphs {
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raw[glyph.Cluster] += glyph.Advance * hScale
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}
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for j := range chars {
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advance := lineAdvances[j]
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if j < len(adjusted) {
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advance = adjusted[j]
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}
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extra[j+1] = extra[j] + advance - raw[j]
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}
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code := TextCode{X: ofdNumber(x), Y: ofdNumber(y), Value: escapeOFDText(string(chars))}
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var dx, dy []string
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var lastX, lastY float64
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for j, glyph := range glyphs {
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gx, gy := x+glyph.X*hScale+extra[glyph.Cluster], y+glyph.Y
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if !finite(gx) || !finite(gy) {
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return fmt.Errorf("shaped position exceeds finite range")
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}
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if j == 0 {
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code.X, code.Y = ofdNumber(gx), ofdNumber(gy)
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} else {
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dx, dy = append(dx, ofdNumber(gx-lastX)), append(dy, ofdNumber(gy-lastY))
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}
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lastX, lastY = gx, gy
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}
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code.DeltaX, code.DeltaY = strings.Join(dx, " "), strings.Join(dy, " ")
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for j := 0; j < len(glyphs); {
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end := j + 1
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for end < len(glyphs) && glyphs[end].Cluster == glyphs[j].Cluster {
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end++
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}
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next := len(chars)
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if end < len(glyphs) {
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next = glyphs[end].Cluster
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}
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ids := make([]string, end-j)
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for k := j; k < end; k++ {
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ids[k-j] = strconv.Itoa(int(glyphs[k].Glyph))
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}
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transforms = append(transforms, CGTransform{CodePosition: offset + glyphs[j].Cluster, CodeCount: next - glyphs[j].Cluster, GlyphCount: end - j, Glyphs: strings.Join(ids, " ")})
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j = end
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}
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codes = append(codes, code)
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offset += len(chars)
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}
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}
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obj.TextCode, obj.CGTransform = codes, transforms
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obj.layout = &textLayout{value: value, options: options}
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return nil
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}
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// shapeTextLine 检查可选后端的簇映射，按原文字符分配塑形步进
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// 入参: shaper 字体塑形器, runes 单行字符, font 字体标识, size 字号, scale 横向比例, spacing 字距
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// 返回: []ShapedGlyph 字形, []float64 含字距的字符步进, error 塑形错误
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func shapeTextLine(shaper FontShaper, runes []rune, font string, size, scale, spacing float64) ([]ShapedGlyph, []float64, error) {
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glyphs, err := shaper.ShapeText(string(runes), size)
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if err != nil {
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return nil, nil, err
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}
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if len(runes) > 0 && (len(glyphs) == 0 || glyphs[0].Cluster != 0) {
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return nil, nil, fmt.Errorf("shaper omitted source text")
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}
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advances := make([]float64, len(runes))
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var missing []rune
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for i, glyph := range glyphs {
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if glyph.Cluster < 0 || glyph.Cluster >= len(runes) || i > 0 && glyph.Cluster < glyphs[i-1].Cluster || !finite(glyph.X) || !finite(glyph.Y) || !finite(glyph.Advance) {
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return nil, nil, fmt.Errorf("invalid shaped glyph")
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}
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if glyph.Glyph == 0 {
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missing = append(missing, runes[glyph.Cluster])
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}
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advances[glyph.Cluster] += glyph.Advance * scale
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}
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if err := missingGlyphError(font, missing); err != nil {
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return nil, nil, err
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}
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for i := 0; i < len(glyphs); {
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end := i + 1
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for end < len(glyphs) && glyphs[end].Cluster == glyphs[i].Cluster {
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end++
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}
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next := len(runes)
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if end < len(glyphs) {
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next = glyphs[end].Cluster
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}
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start := glyphs[i].Cluster
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advance := advances[start] / float64(next-start)
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for j := start; j < next; j++ {
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advances[j] = advance
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}
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i = end
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}
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spaceTextAdvances(runes, advances, spacing)
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if slices.ContainsFunc(advances, func(value float64) bool { return !finite(value) }) {
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return nil, nil, fmt.Errorf("shaped advance exceeds finite range")
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}
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return glyphs, advances, nil
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}
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// shapedLineWidth 计算不含尾随空格和末尾字距的行宽
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// 入参: runes 行内字符, advances 字符步进, spacing 字距
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// 返回: float64 行宽
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func shapedLineWidth(runes []rune, advances []float64, spacing float64) float64 {
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end := len(runes)
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for end > 0 && runes[end-1] == ' ' {
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end--
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}
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width := 0.0
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for _, advance := range advances[:end] {
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width += advance
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}
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if end > 0 {
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width -= spacing
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}
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return width
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}
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// validateTextGlyphs 校验显式字形编号及原文区间，不允许跨TextCode或重叠映射
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// 入参: obj 文字对象, glyphCount 字体字形数量
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// 返回: error 无效映射
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func validateTextGlyphs(obj TextObject, glyphCount uint16) error {
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if len(obj.CGTransform) == 0 {
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return nil
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}
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var ends []int
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total := 0
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for _, code := range obj.TextCode {
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total += len(textCodeRunes(code.Value))
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ends = append(ends, total)
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}
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previous := 0
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for _, transform := range obj.CGTransform {
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start, count := transform.CodePosition, transform.CodeCount
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if start < previous || count <= 0 || start >= total || count > total-start {
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return fmt.Errorf("invalid glyph character range")
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}
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end := start + count
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for _, boundary := range ends {
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if start < boundary {
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if end > boundary {
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return fmt.Errorf("glyph mapping crosses text codes")
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}
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break
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}
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}
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ids := strings.Fields(transform.Glyphs)
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if len(ids) == 0 || len(ids) != transform.GlyphCount {
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return fmt.Errorf("invalid glyph count")
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}
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for _, value := range ids {
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id, err := strconv.ParseUint(value, 10, 16)
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if err != nil || id >= uint64(glyphCount) {
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return fmt.Errorf("invalid glyph index %q", value)
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}
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}
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previous = end
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}
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return nil
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}
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