feat(后端架构): 完善后端解耦

ofdgo_text_layout.go

@@ -0,0 +1,122 @@
+// 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 (
+	"fmt"
+	"math"
+	"slices"
+	"strings"
+	"unicode/utf8"
+)
+
+// LayoutText 按自有字体度量重排横向文字，保留绘制属性，不进行复杂文字塑形
+// 不修改文档，通过AddObject或UpdateObject提交；选项仅供当前编辑过程使用，保存为标准文字定位
+// 入参: obj 文字对象, value 原文, options 段落排版选项, metrics 字体度量
+// 返回: error 错误信息
+func LayoutText(obj *TextObject, value string, options TextLayout, metrics FontMetrics) error {
+	if metrics.UnitsPerEm() == 0 {
+		return fmt.Errorf("font units per em must be positive")
+	}
+	if obj.ReadDirection != 0 || obj.CharDirection != 0 {
+		return fmt.Errorf("automatic text layout requires horizontal text")
+	}
+	if !finite(obj.Size) || obj.Size <= 0 || !finite(obj.HScale) || obj.HScale < 0 {
+		return fmt.Errorf("invalid text dimensions")
+	}
+	value = strings.ReplaceAll(strings.ReplaceAll(value, "\r\n", "\n"), "\r", "\n")
+	if !utf8.ValidString(value) || strings.Contains(value, "\t") || strings.Trim(value, "\n") == "" {
+		return fmt.Errorf("text must contain UTF-8 characters without tabs")
+	}
+	lineHeight := options.LineHeight
+	if !finite(lineHeight) || lineHeight < 0 {
+		return fmt.Errorf("line height must be finite and nonnegative")
+	}
+	if !finite(options.LetterSpacing) {
+		return fmt.Errorf("letter spacing must be finite")
+	}
+	if !finite(options.LeftIndent) || !finite(options.RightIndent) || !finite(options.FirstLineIndent) {
+		return fmt.Errorf("paragraph indents must be finite")
+	}
+	if !slices.Contains([]string{"", "left", "center", "right", "justify"}, options.Align) {
+		return fmt.Errorf("invalid text alignment %q", options.Align)
+	}
+	var width float64
+	if options.Wrap || options.Align != "" && options.Align != "left" || options.LeftIndent != 0 || options.RightIndent != 0 || options.FirstLineIndent != 0 {
+		box, err := obj.TextFrame()
+		if err != nil {
+			return err
+		}
+		width = box.W - options.LeftIndent - options.RightIndent
+		if !finite(width) || width <= 0 || !finite(width-options.FirstLineIndent) || width-options.FirstLineIndent <= 0 {
+			return fmt.Errorf("paragraph indents leave no text width")
+		}
+	}
+	hScale := obj.HScale
+	if hScale == 0 {
+		hScale = 1
+	}
+	ascender, descender, gap := metrics.VerticalMetrics()
+	unit := obj.Size / float64(metrics.UnitsPerEm())
+	if lineHeight == 0 {
+		lineHeight = math.Max(obj.Size, float64(int(ascender)+int(descender)+int(gap))*unit)
+	}
+	var codes []TextCode
+	var missing []rune
+	for _, paragraph := range strings.Split(value, "\n") {
+		runes := []rune(paragraph)
+		advances := make([]float64, len(runes))
+		for i, char := range runes {
+			glyph := metrics.GlyphIndex(char)
+			if glyph == 0 {
+				missing = append(missing, char)
+				continue
+			}
+			advances[i] = float64(metrics.GlyphAdvance(glyph)) * unit * hScale
+		}
+		if len(missing) != 0 {
+			continue
+		}
+		spaceTextAdvances(runes, advances, options.LetterSpacing)
+		for _, advance := range advances {
+			if !finite(advance) {
+				return fmt.Errorf("text advance exceeds finite range")
+			}
+		}
+		lines := breakTextLines(runes, advances, width, options.Wrap, options.LetterSpacing, options.FirstLineIndent)
+		for i, line := range lines {
+			indent := 0.0
+			if i == 0 {
+				indent = options.FirstLineIndent
+			}
+			x, deltas := alignTextLine(runes[line[0]:line[1]], advances[line[0]:line[1]], width-indent, options.Align, i+1 < len(lines), options.LetterSpacing)
+			x += options.LeftIndent + indent
+			y := float64(ascender)*unit + float64(len(codes))*lineHeight
+			if !finite(x) || !finite(y) {
+				return fmt.Errorf("text position exceeds finite range")
+			}
+			codes = append(codes, TextCode{X: ofdNumber(x), Y: ofdNumber(y), DeltaX: deltas, Value: escapeOFDText(string(runes[line[0]:line[1]]))})
+		}
+	}
+	if err := missingGlyphError(obj.Font, missing); err != nil {
+		return err
+	}
+	obj.TextCode = codes
+	obj.layout = nil
+	if options != (TextLayout{}) {
+		obj.layout = &textLayout{value: value, options: options}
+	}
+	return nil
+}