M6: the open-subpath fixture covers stroke-first paint order

A third row in open_subpaths.svg: a filled and stroked path that is only
0.001 short stays one layer, and an open triangle with
paint-order="stroke" puts its stroke layer under its fill layer.

crates/svg/tests/corpus.rs

@@ -257,8 +257,11 @@ fn fills_close_open_subpaths() {
     let (fill, stroke) = (layer(&d, f, "stroked fill"), layer(&d, f, "stroked"));
     assert_eq!((loops(fill), fill.fills.len(), fill.strokes.len()), (2, 1, 0));
     assert_eq!((loops(stroke), stroke.fills.len(), stroke.strokes.len()), (0, 0, 1));
+    // Only near-closed ends: one layer, closed, stroke and all.
+    let near = layer(&d, f, "near");
+    assert_eq!((loops(near), near.fills.len(), near.strokes.len()), (1, 1, 1));
     let order: Vec<&str> = d.node(f).unwrap().children.iter().filter_map(|c| d.node(*c)).map(|n| n.name.as_str()).collect();
-    assert_eq!(order, ["filled", "stroked fill", "stroked"], "the fill paints first, as SVG paints fill then stroke");
+    assert_eq!(order, ["filled", "stroked fill", "stroked", "near", "under", "under fill"], "paint order: fill then stroke, or the stroke first");
 }
 
 #[test]

crates/svg/tests/corpus/open_subpaths.svg

@@ -1,10 +1,14 @@
-<svg xmlns="http://www.w3.org/2000/svg" width="200" height="80">
+<svg xmlns="http://www.w3.org/2000/svg" width="200" height="120">
   <!-- Fill closes every subpath (SVG painting: "fill ... as if a closepath"). Top row, one filled
        path: closed with Z; back on its start without Z; 0.001 short of its start without Z (what
        PDF exports rounded to three decimals write); an open triangle. Bottom row, filled and
-       stroked: 0.001 short (closed, stroke and all); an open triangle (stroked open). -->
+       stroked: 0.001 short (closed, stroke and all); an open triangle (stroked open). Third row,
+       filled and stroked: only 0.001 short (one layer); an open triangle with its stroke under
+       the fill. -->
   <path id="filled" fill="#000000" d="M10 10h20v20h-20z M50 10h20v20h-20v-20 M90 10h20v20h-20v-19.999 M130 10h20v20"/>
   <path id="stroked" fill="#000000" stroke="#ff0000" stroke-width="2" d="M10 50h20v20h-20v-19.999 M130 50h20v20"/>
+  <path id="near" fill="#000000" stroke="#ff0000" stroke-width="2" d="M50 90h20v20h-20v-19.999"/>
+  <path id="under" fill="#000000" stroke="#ff0000" stroke-width="2" paint-order="stroke" d="M130 90h20v20"/>
   <!-- probe 20 20 #000000ff -->
   <!-- probe 60 20 #000000ff -->
   <!-- probe 100 20 #000000ff -->
@@ -15,4 +19,10 @@
   <!-- probe 140 50 #ff0000ff -->
   <!-- probe 145 55 #000000ff -->
   <!-- probe 135 65 #00000000 -->
+  <!-- probe 60 100 #000000ff -->
+  <!-- probe 50 100 #ff0000ff -->
+  <!-- probe 140 89 #ff0000ff -->
+  <!-- probe 140 90 #000000ff -->
+  <!-- probe 145 95 #000000ff -->
+  <!-- probe 135 105 #00000000 -->
 </svg>