svg-maker: svgc - .svgd text format -> SVG for agent-helm sharing

Line-based DSL (shapes, text, groups, color vars) with strict
validation and line-numbered errors, SVG emitter with visibility
defaults, truecolor terminal preview (same half-block technique as
spritec), info with bbox + outside-canvas warnings. Verified
end-to-end: svgc build -> helmd share -> visible through the hub.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011KikHkfCiC3yELbsMN8fT9

svg-maker/svg/path.go

@@ -0,0 +1,195 @@
+package svg
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// flattenPath turns a path-data subset (M L H V C Q Z, absolute and
+// relative) into one or more polylines, used for validation, preview
+// rasterization and measurements. Curves become 16 line segments.
+func flattenPath(d string) ([][][2]float64, error) {
+	tokens, err := pathTokens(d)
+	if err != nil {
+		return nil, err
+	}
+	var subpaths [][][2]float64
+	var cur [][2]float64
+	var x, y, startX, startY float64
+	i := 0
+	cmd := ""
+
+	need := func(n int) ([]float64, error) {
+		if i+n > len(tokens) {
+			return nil, fmt.Errorf("command %s needs %d numbers", cmd, n)
+		}
+		out := make([]float64, n)
+		for j := 0; j < n; j++ {
+			v, err := strconv.ParseFloat(tokens[i+j], 64)
+			if err != nil {
+				return nil, fmt.Errorf("command %s: %q is not a number", cmd, tokens[i+j])
+			}
+			out[j] = v
+		}
+		i += n
+		return out, nil
+	}
+	flush := func() {
+		if len(cur) > 1 {
+			subpaths = append(subpaths, cur)
+		}
+		cur = nil
+	}
+
+	for i < len(tokens) {
+		t := tokens[i]
+		if len(t) == 1 && strings.ContainsAny(t, "MLHVCQZmlhvcqz") {
+			cmd = t
+			i++
+			if cmd == "Z" || cmd == "z" {
+				if len(cur) > 0 {
+					cur = append(cur, [2]float64{startX, startY})
+					x, y = startX, startY
+				}
+				flush()
+				continue
+			}
+		} else if cmd == "" {
+			return nil, fmt.Errorf("path must start with M/m, got %q", t)
+		}
+		// repeated coordinate groups reuse the current command
+		rel := cmd >= "a" // lowercase = relative
+		switch strings.ToUpper(cmd) {
+		case "M":
+			n, err := need(2)
+			if err != nil {
+				return nil, err
+			}
+			if rel {
+				n[0] += x
+				n[1] += y
+			}
+			flush()
+			x, y = n[0], n[1]
+			startX, startY = x, y
+			cur = [][2]float64{{x, y}}
+			cmd = map[bool]string{true: "l", false: "L"}[rel] // subsequent pairs are implicit lineto
+		case "L":
+			n, err := need(2)
+			if err != nil {
+				return nil, err
+			}
+			if rel {
+				n[0] += x
+				n[1] += y
+			}
+			x, y = n[0], n[1]
+			cur = append(cur, [2]float64{x, y})
+		case "H":
+			n, err := need(1)
+			if err != nil {
+				return nil, err
+			}
+			if rel {
+				n[0] += x
+			}
+			x = n[0]
+			cur = append(cur, [2]float64{x, y})
+		case "V":
+			n, err := need(1)
+			if err != nil {
+				return nil, err
+			}
+			if rel {
+				n[0] += y
+			}
+			y = n[0]
+			cur = append(cur, [2]float64{x, y})
+		case "Q":
+			n, err := need(4)
+			if err != nil {
+				return nil, err
+			}
+			if rel {
+				n[0] += x
+				n[1] += y
+				n[2] += x
+				n[3] += y
+			}
+			for s := 1; s <= 16; s++ {
+				t := float64(s) / 16
+				u := 1 - t
+				px := u*u*x + 2*u*t*n[0] + t*t*n[2]
+				py := u*u*y + 2*u*t*n[1] + t*t*n[3]
+				cur = append(cur, [2]float64{px, py})
+			}
+			x, y = n[2], n[3]
+		case "C":
+			n, err := need(6)
+			if err != nil {
+				return nil, err
+			}
+			if rel {
+				n[0] += x
+				n[1] += y
+				n[2] += x
+				n[3] += y
+				n[4] += x
+				n[5] += y
+			}
+			for s := 1; s <= 16; s++ {
+				t := float64(s) / 16
+				u := 1 - t
+				px := u*u*u*x + 3*u*u*t*n[0] + 3*u*t*t*n[2] + t*t*t*n[4]
+				py := u*u*u*y + 3*u*u*t*n[1] + 3*u*t*t*n[3] + t*t*t*n[5]
+				cur = append(cur, [2]float64{px, py})
+			}
+			x, y = n[4], n[5]
+		default:
+			return nil, fmt.Errorf("unsupported path command %q (supported: M L H V C Q Z)", cmd)
+		}
+	}
+	flush()
+	if len(subpaths) == 0 {
+		return nil, fmt.Errorf("path draws nothing")
+	}
+	return subpaths, nil
+}
+
+// pathTokens splits path data into command letters and numbers.
+func pathTokens(d string) ([]string, error) {
+	var out []string
+	var cur strings.Builder
+	flush := func() {
+		if cur.Len() > 0 {
+			out = append(out, cur.String())
+			cur.Reset()
+		}
+	}
+	for _, r := range d {
+		switch {
+		case r == ' ' || r == '\t' || r == ',':
+			flush()
+		case (r >= 'A' && r <= 'Z') || (r >= 'a' && r <= 'z'):
+			flush()
+			out = append(out, string(r))
+		case (r >= '0' && r <= '9') || r == '.' || r == 'e' || r == 'E':
+			cur.WriteRune(r)
+		case r == '-' || r == '+':
+			// sign starts a new number unless it follows an exponent
+			s := cur.String()
+			if cur.Len() > 0 && !strings.HasSuffix(s, "e") && !strings.HasSuffix(s, "E") {
+				flush()
+			}
+			cur.WriteRune(r)
+		default:
+			return nil, fmt.Errorf("unexpected character %q in path data", r)
+		}
+	}
+	flush()
+	if len(out) == 0 {
+		return nil, fmt.Errorf("empty path data")
+	}
+	return out, nil
+}