feat(创建编辑): 新增基础图形绘制与样式设置，完善缩放和撤销重做

ofdgo_shape.go

@@ -0,0 +1,64 @@
+// 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"
+)
+
+// ShapeKind 基本图形类型
+type ShapeKind string
+
+const (
+	ShapeLine      ShapeKind = "line"
+	ShapeRectangle ShapeKind = "rectangle"
+	ShapeEllipse   ShapeKind = "ellipse"
+)
+
+// NewShape 创建使用标准紧缩路径的图形，默认黑色描边、不填充。
+// 可调整返回对象的颜色、线宽等属性后通过 Editor.AddObject 写入。
+// 入参: kind 图形类型, box 图形范围；直线从 (X,Y) 到 (X+W,Y+H)，W、H 可为负或零
+// 返回: PathObject 路径对象, error 错误信息
+func NewShape(kind ShapeKind, box Box) (PathObject, error) {
+	if !finite(box.X) || !finite(box.Y) || !finite(box.W) || !finite(box.H) || !finite(box.X+box.W) || !finite(box.Y+box.H) {
+		return PathObject{}, fmt.Errorf("shape coordinates must be finite")
+	}
+	object := PathObject{LineWidth: defaultPathLineWidth}
+	switch kind {
+	case ShapeLine:
+		if box.W == 0 && box.H == 0 {
+			return PathObject{}, fmt.Errorf("line endpoints must differ")
+		}
+		// 为水平、垂直直线保留有效的正尺寸边界，路径端点不变。
+		x, y := math.Min(0, box.W)-defaultPathLineWidth/2, math.Min(0, box.H)-defaultPathLineWidth/2
+		object.AbbreviatedData = fmt.Sprintf("M %g %g L %g %g", -x, -y, box.W-x, box.H-y)
+		box = Box{X: box.X + x, Y: box.Y + y, W: math.Abs(box.W) + defaultPathLineWidth, H: math.Abs(box.H) + defaultPathLineWidth}
+	case ShapeRectangle, ShapeEllipse:
+		if box.W <= 0 || box.H <= 0 {
+			return PathObject{}, fmt.Errorf("shape dimensions must be positive")
+		}
+		if kind == ShapeRectangle {
+			object.AbbreviatedData = fmt.Sprintf("M 0 0 L %g 0 L %g %g L 0 %g C", box.W, box.W, box.H, box.H)
+		} else {
+			rx, ry := box.W/2, box.H/2
+			object.AbbreviatedData = fmt.Sprintf("M 0 %g A %g %g 0 0 1 %g %g A %g %g 0 0 1 0 %g C", ry, rx, ry, box.W, ry, rx, ry, ry)
+		}
+	default:
+		return PathObject{}, fmt.Errorf("unsupported shape %q", kind)
+	}
+	object.Boundary = fmt.Sprintf("%g %g %g %g", box.X, box.Y, box.W, box.H)
+	return object, nil
+}