feat(后端架构): 优化多后端渲染，修复描边与字形校验

ofdgo_renderer_stroke_gg.go

@@ -0,0 +1,97 @@
+// 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"
+
+// ggNativeStroke 判断GG当前可保真处理的描边范围
+// 入参: command 描边指令, scale 每毫米像素数
+// 返回: bool 是否可使用原生描边
+func ggNativeStroke(command RasterCommand, scale float64) bool {
+	if command.Paint.Gradient != nil && command.Stroke.Width*scale < 1 {
+		return false
+	}
+	joins := command.Stroke.Join == "" || command.Stroke.Join == "Miter"
+	dashed := false
+	for _, value := range command.Stroke.Dashes {
+		dashed = dashed || value > 0
+	}
+	segments := 0
+	for _, segment := range command.Path {
+		switch segment.Verb {
+		case RasterMove:
+			segments = 0
+		case RasterLine, RasterQuad, RasterCubic:
+			segments++
+			if joins && segments > 1 {
+				return false
+			}
+			if dashed && segment.Verb != RasterLine {
+				return false
+			}
+		case RasterClose:
+			if dashed || joins {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+// expandStroke 使用显式几何提供者展开GG尚不可靠的描边，不切换光栅后端
+// 入参: command 描边指令
+// 返回: RasterCommand 等价填充指令, error 能力或几何错误
+func (b GGBackend) expandStroke(command RasterCommand) (RasterCommand, error) {
+	if b.StrokeGeometry == nil {
+		return RasterCommand{}, fmt.Errorf("GG stroke geometry: %w", ErrBackendUnavailable)
+	}
+	values := command.Transform
+	matrix := Matrix{a: values[0], b: values[1], c: values[2], d: values[3], e: values[4], f: values[5]}
+	path, err := b.StrokeGeometry.Transform(geometryFromRaster(command.Path), matrix)
+	if err != nil {
+		return RasterCommand{}, err
+	}
+	path, err = b.StrokeGeometry.Stroke(path, *command.Stroke)
+	if err != nil {
+		return RasterCommand{}, err
+	}
+	path, err = path.Curves(.0001)
+	if err != nil {
+		return RasterCommand{}, err
+	}
+	if command.Paint.Gradient != nil {
+		inverse, ok := matrix.Invert()
+		if !ok {
+			return RasterCommand{}, fmt.Errorf("invalid stroke gradient transform")
+		}
+		path, err = b.StrokeGeometry.Transform(path, inverse)
+		if err != nil {
+			return RasterCommand{}, err
+		}
+	} else {
+		command.Transform = RasterMatrix{1, 0, 0, 1, 0, 0}
+	}
+	command.Path = make([]RasterSegment, len(path))
+	for i, s := range path {
+		verb := RasterVerb(s.Verb)
+		if s.Verb == GeometryClose {
+			verb = RasterClose
+		}
+		command.Path[i] = RasterSegment{Verb: verb, End: RasterPoint{s.End.X, s.End.Y}, Control1: RasterPoint{s.Control1.X, s.Control1.Y}, Control2: RasterPoint{s.Control2.X, s.Control2.Y}}
+	}
+	command.Stroke = nil
+	command.EvenOdd = false
+	return command, nil
+}