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/emit.go

@@ -0,0 +1,135 @@
+package svg
+
+import (
+	"fmt"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+// Emit renders the document as an SVG file.
+func Emit(d *Doc) string {
+	var b strings.Builder
+	fmt.Fprintf(&b, `<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 %s %s" width="%s" height="%s">`,
+		num(d.W), num(d.H), num(d.W), num(d.H))
+	b.WriteString("\n")
+	if d.Bg != "" {
+		fmt.Fprintf(&b, `  <rect width="100%%" height="100%%" fill="%s"/>`+"\n", d.Bg)
+	}
+	for _, el := range d.Elems {
+		emitElem(&b, el, 1)
+	}
+	b.WriteString("</svg>\n")
+	return b.String()
+}
+
+func emitElem(b *strings.Builder, el *Elem, depth int) {
+	ind := strings.Repeat("  ", depth)
+	attrs := attrString(el.Attrs)
+	switch el.Kind {
+	case "rect":
+		fmt.Fprintf(b, `%s<rect x="%s" y="%s" width="%s" height="%s"%s/>`+"\n",
+			ind, num(el.Nums[0]), num(el.Nums[1]), num(el.Nums[2]), num(el.Nums[3]), attrs)
+	case "circle":
+		fmt.Fprintf(b, `%s<circle cx="%s" cy="%s" r="%s"%s/>`+"\n",
+			ind, num(el.Nums[0]), num(el.Nums[1]), num(el.Nums[2]), attrs)
+	case "ellipse":
+		fmt.Fprintf(b, `%s<ellipse cx="%s" cy="%s" rx="%s" ry="%s"%s/>`+"\n",
+			ind, num(el.Nums[0]), num(el.Nums[1]), num(el.Nums[2]), num(el.Nums[3]), attrs)
+	case "line":
+		fmt.Fprintf(b, `%s<line x1="%s" y1="%s" x2="%s" y2="%s"%s/>`+"\n",
+			ind, num(el.Nums[0]), num(el.Nums[1]), num(el.Nums[2]), num(el.Nums[3]), attrs)
+	case "polyline", "polygon":
+		pts := make([]string, len(el.Points))
+		for i, p := range el.Points {
+			pts[i] = num(p[0]) + "," + num(p[1])
+		}
+		fmt.Fprintf(b, `%s<%s points="%s"%s/>`+"\n", ind, el.Kind, strings.Join(pts, " "), attrs)
+	case "path":
+		fmt.Fprintf(b, `%s<path d="%s"%s/>`+"\n", ind, escape(el.D), attrs)
+	case "text":
+		fmt.Fprintf(b, `%s<text x="%s" y="%s"%s>%s</text>`+"\n",
+			ind, num(el.Nums[0]), num(el.Nums[1]), attrs, escape(el.Text))
+	case "group":
+		fmt.Fprintf(b, "%s<g%s>\n", ind, attrs)
+		for _, kid := range el.Kids {
+			emitElem(b, kid, depth+1)
+		}
+		fmt.Fprintf(b, "%s</g>\n", ind)
+	}
+}
+
+// defaults SVG would otherwise pick that surprise agents: lines and
+// paths get a visible stroke if none set; polyline defaults fill=none
+// so it doesn't render as a filled blob.
+func effectiveAttrs(el *Elem) map[string]string {
+	out := map[string]string{}
+	for k, v := range el.Attrs {
+		out[k] = v
+	}
+	switch el.Kind {
+	case "line", "polyline":
+		if out["stroke"] == "" {
+			out["stroke"] = "black"
+		}
+		if el.Kind == "polyline" && out["fill"] == "" {
+			out["fill"] = "none"
+		}
+	case "path":
+		if out["stroke"] == "" && out["fill"] == "" {
+			out["stroke"] = "black"
+			out["fill"] = "none"
+		}
+	}
+	return out
+}
+
+func attrString(attrs map[string]string) string {
+	if len(attrs) == 0 {
+		return ""
+	}
+	keys := make([]string, 0, len(attrs))
+	for k := range attrs {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+	var b strings.Builder
+	for _, k := range keys {
+		fmt.Fprintf(&b, ` %s="%s"`, k, escape(attrs[k]))
+	}
+	return b.String()
+}
+
+func num(f float64) string {
+	return strconv.FormatFloat(f, 'f', -1, 64)
+}
+
+func escape(s string) string {
+	r := strings.NewReplacer("&", "&amp;", "<", "&lt;", ">", "&gt;", `"`, "&quot;")
+	return r.Replace(s)
+}
+
+// normalize applies the effective attrs (visibility defaults) onto the
+// tree before emit/raster so both outputs agree.
+func (d *Doc) normalize() {
+	var walk func(els []*Elem)
+	walk = func(els []*Elem) {
+		for _, el := range els {
+			el.Attrs = effectiveAttrs(el)
+			if el.Kind == "group" {
+				walk(el.Kids)
+			}
+		}
+	}
+	walk(d.Elems)
+}
+
+// Build parses src and emits SVG in one step.
+func Build(src string) (string, *Doc, error) {
+	doc, err := Parse(src)
+	if err != nil {
+		return "", nil, err
+	}
+	doc.normalize()
+	return Emit(doc), doc, nil
+}