fix(symbols): render S-101 even-odd danger symbols with their holes

go.mod

@@ -10,6 +10,7 @@ require (
 	github.com/dhconnelly/rtreego v1.2.0
 	github.com/srwiley/oksvg v0.0.0-20221011165216-be6e8873101c
 	github.com/srwiley/rasterx v0.0.0-20220730225603-2ab79fcdd4ef
+	github.com/srwiley/scanFT v0.0.0-20220128184157-0d1ee492111f
 	github.com/stretchr/testify v1.11.1
 	github.com/yuin/gopher-lua v1.1.2
 	golang.org/x/image v0.43.0

go.sum

@@ -35,6 +35,8 @@ github.com/srwiley/oksvg v0.0.0-20221011165216-be6e8873101c h1:km8GpoQut05eY3GiY
 github.com/srwiley/oksvg v0.0.0-20221011165216-be6e8873101c/go.mod h1:cNQ3dwVJtS5Hmnjxy6AgTPd0Inb3pW05ftPSX7NZO7Q=
 github.com/srwiley/rasterx v0.0.0-20220730225603-2ab79fcdd4ef h1:Ch6Q+AZUxDBCVqdkI8FSpFyZDtCVBc2VmejdNrm5rRQ=
 github.com/srwiley/rasterx v0.0.0-20220730225603-2ab79fcdd4ef/go.mod h1:nXTWP6+gD5+LUJ8krVhhoeHjvHTutPxMYl5SvkcnJNE=
+github.com/srwiley/scanFT v0.0.0-20220128184157-0d1ee492111f h1:uLR2GaV0kWYZ3Ns3l3sjtiN+mOWAQadvrL8HXcyKjl0=
+github.com/srwiley/scanFT v0.0.0-20220128184157-0d1ee492111f/go.mod h1:LZwgIPG9X6nH6j5Ef+xMFspl6Hru4b5EJxzMfeqHYJY=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
 github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=

pkg/s100/symbols/symbols.go

@@ -3,10 +3,13 @@
 // and rasterizes them in pure Go. It is the single source of truth for
 // SVG→raster, used by the sprite-atlas builder.
 //
-// Two oksvg defects are worked around here: it ignores a non-zero viewBox
-// origin (we normalize to "0 0 W H" and wrap the content in a translate), and
-// it applies stroke-width in device px without scaling by the draw transform
-// (we pre-multiply stroke-width by the px/mm scale).
+// Three oksvg/rasterx defects are worked around here: oksvg ignores a non-zero
+// viewBox origin (we normalize to "0 0 W H" and wrap the content in a
+// translate); it applies stroke-width in device px without scaling by the draw
+// transform (we pre-multiply stroke-width by the px/mm scale); and it ignores
+// the fill-rule attribute while rasterx's ScannerGV cannot do even-odd fills at
+// all (we force even-odd winding and rasterize through scanFT, which honours
+// it) so the catalogue's even-odd danger symbols don't fill their holes solid.
 package symbols
 
 import (
@@ -23,6 +26,7 @@ import (
 
 	"github.com/srwiley/oksvg"
 	"github.com/srwiley/rasterx"
+	"github.com/srwiley/scanFT"
 )
 
 var cssRuleRE = regexp.MustCompile(`\.([A-Za-z0-9_]+)\s*\{([^}]*)\}`)
@@ -58,14 +62,28 @@ func Render(svg []byte, css map[string]string, pxPerMM float64) (*Rendered, erro
 	if err != nil {
 		return nil, err
 	}
+	// oksvg ignores the SVG fill-rule attribute and always fills with the
+	// nonzero winding rule. Every S-101 symbol is authored with
+	// fill-rule="evenodd": the danger hatch of ISODGR01/DANGER0x and similar
+	// glyphs is a single compound path whose inner subpath is a hole, and
+	// nonzero winding fills that hole solid (an ISODGR01 with no star in it).
+	// Force even-odd winding on every path so the holes render. For simple,
+	// non-self-intersecting paths even-odd and nonzero are identical, so this
+	// is safe for the rest of the set.
+	for i := range icon.SVGPaths {
+		icon.SVGPaths[i].UseNonZeroWinding = false
+	}
 	w := int(math.Ceil(vb[2] * pxPerMM))
 	h := int(math.Ceil(vb[3] * pxPerMM))
 	if w < 1 || h < 1 {
 		return nil, fmt.Errorf("degenerate viewBox %gx%g", vb[2], vb[3])
 	}
 	rgba := image.NewRGBA(image.Rect(0, 0, w, h))
 	icon.SetTarget(0, 0, float64(w), float64(h))
-	scanner := rasterx.NewScannerGV(w, h, rgba, rgba.Bounds())
+	// scanFT (freetype-backed) honours the even-odd winding set above;
+	// rasterx's own ScannerGV silently ignores it (it is nonzero-only), which
+	// fills the danger-symbol holes solid.
+	scanner := scanFT.NewScannerFT(w, h, scanFT.NewRGBAPainter(rgba))
 	icon.Draw(rasterx.NewDasher(w, h, scanner), 1.0)
 
 	// rasterx writes alpha-premultiplied RGBA; draw.Src into NRGBA converts to

pkg/s100/symbols/symbols_test.go

@@ -0,0 +1,38 @@
+package symbols
+
+import "testing"
+
+// TestRenderEvenOddHole guards the fill-rule="evenodd" handling. Every S-101
+// symbol is authored with even-odd winding; the ISODGR01/DANGER0x danger glyphs
+// carve their inner shape out of the outer body with a single compound path
+// whose inner subpath is a hole. oksvg ignores fill-rule and fills nonzero,
+// which would fill that hole solid (the "ISODGR01 with no star in it" bug).
+func TestRenderEvenOddHole(t *testing.T) {
+	// Outer 8x8 square with a concentric 4x4 inner subpath, both wound the same
+	// way. Under nonzero winding the inner square fills solid; under even-odd it
+	// is a hole. fill-rule="evenodd" sits on the root <svg> exactly as the
+	// catalogue authors it.
+	svg := []byte(`<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="-5 -5 10 10" fill-rule="evenodd">
+  <path class="fX" d="M -4,-4 L 4,-4 L 4,4 L -4,4 L -4,-4 Z M -2,-2 L 2,-2 L 2,2 L -2,2 L -2,-2 Z"/>
+</svg>`)
+	css := map[string]string{"fX": "fill:#C045D1"}
+
+	const pxPerMM = 10
+	r, err := Render(svg, css, pxPerMM)
+	if err != nil {
+		t.Fatalf("Render: %v", err)
+	}
+
+	// Pivot is the SVG origin (0,0); the hole is centred there.
+	cx, cy := int(r.PivotX), int(r.PivotY)
+	if _, _, _, a := r.Image.At(cx, cy).RGBA(); a != 0 {
+		t.Errorf("centre pixel (%d,%d) alpha=%d, want 0 (even-odd hole filled solid — fill-rule ignored)", cx, cy, a>>8)
+	}
+
+	// A pixel in the ring between the two squares must be painted.
+	rx, ry := int(r.PivotX+3*pxPerMM), cy // svg (3,0)
+	if _, _, _, a := r.Image.At(rx, ry).RGBA(); a == 0 {
+		t.Errorf("ring pixel (%d,%d) is transparent, want painted", rx, ry)
+	}
+}