Offset of an irregular closed spline no longer fails its error certificate; offset fit nodes stay private (#1009)

Fixes #971. At the node limit the offset certificate splits the fitted curve where it meets the exact offset midpoint, so curves with different parameter speeds certify within the same 0.002 mm tolerance. Associated offset fit nodes are hidden from display, picking, box selection and snapping until Break Association.

Thanks @Karl-VonRichter.

crates/ui-egui/src/viewport.rs

@@ -853,8 +853,9 @@ fn pick_hits(app: &SolveApp, proj: &Proj, pos: Pos2, other_sketch_points: bool,
     for ss in point_sketches.iter().filter_map(|sid| st.sketch(*sid)) {
         let sid = ss.feature;
         let shown = snapping.then(|| crate::dialogs::SnapPoints::of(&ss.sketch));
+        let visible = solidcraft_engine::view::SketchPointVisibility::new(&ss.sketch);
         for p in &ss.sketch.points {
-            if shown.as_ref().is_some_and(|f| !f.takes(p)) {
+            if !visible.takes(p) || shown.as_ref().is_some_and(|f| !f.takes(p)) {
                 continue;
             }
             if let Some(sp) = proj.to_screen(ss.plane.to_world(p.pos)) {
@@ -2586,10 +2587,11 @@ fn box_select(app: &mut SolveApp, proj: &Proj, bx: BoxSel, add: bool) {
                 out.push(Sel::SketchCurve { id: c.id.clone() });
             }
         }
+        let visible = solidcraft_engine::view::SketchPointVisibility::new(&ss.sketch);
         for (i, p) in ss.sketch.points.iter().enumerate().filter(|_| !off("sketch") && !off("sketch_points")) {
             if accepts.is_none_or(|a| a & crate::selection::SKETCH_POINTS != 0)
                 && i != 0
-                && solidcraft_engine::view::sketch_point_visible(&ss.sketch, i)
+                && visible.takes(p)
                 && bx.takes(&to2(&[ss.plane.to_world(p.pos)]))
             {
                 out.push(Sel::SketchPoint { id: p.id.clone() });
@@ -2763,8 +2765,9 @@ fn overlays(app: &SolveApp, painter: &egui::Painter, proj: &Proj) {
     let sk = &ss.sketch;
     let locked = sk.locked_points();
     let virtual_corners: Vec<usize> = sk.virtual_corners().into_iter().map(|(i, _)| i).collect();
+    let visible = solidcraft_engine::view::SketchPointVisibility::new(sk);
     for (i, p) in sk.points.iter().enumerate() {
-        if !solidcraft_engine::view::sketch_point_visible(sk, i) {
+        if !visible.takes(p) {
             continue;
         }
         let hidden = (sk.view.hide_points && i != 0) || (sk.view.hide_projected && p.link.is_some());