PDF export: warn about spot stops in freeform gradients without points

A freeform gradient whose field has no points of its own takes its
colors from the stops, so spot-linked stops in it are written in
process colors too. The export now warns in that case, as it does for
the other gradients drawn as images.

crates/engine/src/tests/linked_stops.rs

@@ -321,3 +321,19 @@ fn spot_gradients_drawn_as_images_warn() {
     assert!(pdf.contains("/Subtype/Image") && !pdf.contains("/Separation"), "a process Perceptual gradient");
     assert!(!spot_warning(&warnings), "{warnings:?}");
 }
+
+#[test]
+fn freeform_gradients_without_points_warn_about_spot_stops() {
+    let (mut s, id) = setup();
+    run(&mut s, "paint.editGradient", with(ink_to_white(100.0), json!({"kind": "freeform"})));
+    // A freeform field with no points of its own: the colors come from the stops, the first
+    // linked to the spot swatch.
+    let mut g = gradient(&s, id);
+    g.freeform = Some(vectorcraft_color::Freeform::default());
+    g.gradient.stops[0].swatch = Some("Ink".into());
+    let d = std::sync::Arc::make_mut(&mut s.doc_mut().unwrap().doc);
+    d.node_mut(id).unwrap().appearance.set_fill(Paint::Gradient(Box::new(g)));
+    let (pdf, warnings) = pdf_of(&s);
+    assert!(pdf.contains("/Subtype/Image"), "an image");
+    assert!(warnings.iter().any(|w| w.contains("spot colors in gradients exported as images")), "{warnings:?}");
+}

crates/pdf/src/export/paint.rs

@@ -431,7 +431,7 @@ impl Exporter<'_> {
     /// in process colors, so the spot inks have no plate of their own.
     fn warn_spot_image(&mut self, g: &vectorcraft_color::GradientPaint) {
         let doc = self.doc;
-        let from_stops = g.gradient.kind != GradientKind::Freeform || g.freeform.is_none();
+        let from_stops = g.gradient.kind != GradientKind::Freeform || !g.has_freeform_points();
         if from_stops && g.gradient.stops.iter().any(|s| s.swatch.as_deref().is_some_and(|n| doc.swatch(n).is_some_and(|w| w.spot))) {
             self.warn(
                 "spot colors in gradients exported as images (freeform or dithered gradients, and Perceptual ones with RGB or Lab stops or too many stops) are written in process colors",