fix: review fixes for the metric template and the radial constraint

A new drawing (#1441) recorded ISO-25 as the current dimension style by
name only. Every other place that changes it sets the header's handle as
well, and a DWG carries the current style by handle alone, so a saved new
drawing reopened on Standard. The style's handle now comes back from the
helper that adds it.

A radius constraint (#1443) anchored the circle's centre from the shape of
its references — one whole entity — but a single whole reference is also a
line's length, whose start is what stays. The entity decides now.

The two tests that encoded the replaced rules follow them: a negative
radius validates by its magnitude, as a negative distance already did, and
only zero is refused; a new drawing's dimension text reads at ISO-25's
comma separator.

Co-Authored-By: Claude Opus 5 <[email protected]>

src/app/dimension_preview_tests.rs

@@ -63,7 +63,9 @@ fn ordinate_preview_matches_commit() {
     assert!(app.dimension_preview_entities(i, DVec3::ZERO).is_none());
     let _ = app.feed_command(StepInput::Point(DVec3::new(12.5, 40.0, 0.0)));
     let entity = commit_and_compare(&mut app, i, DVec3::new(12.5, 90.0, 0.0));
-    assert_eq!(text(&app, &entity), "12.5");
+    // A new drawing is metric and current on ISO-25, whose decimal separator
+    // is a comma and whose trailing zeros are suppressed.
+    assert_eq!(text(&app, &entity), "12,5");
 }
 
 #[test]

src/scene/creation_style.rs

@@ -36,14 +36,16 @@ fn named_text_style(doc: &CadDocument, name: &str) -> Option<TextStyle> {
 }
 
 /// Adds the reference's ISO-25 dimension style (the current style of its
-/// metric template) when the drawing has none of that name.
-pub fn ensure_iso_dim_style(doc: &mut CadDocument) {
-    if doc
+/// metric template) when the drawing has none of that name, and hands back its
+/// handle: the header records the current dimension style by handle as well as
+/// by name, and a DWG carries only the handle.
+pub fn ensure_iso_dim_style(doc: &mut CadDocument) -> Handle {
+    if let Some(style) = doc
         .dim_styles
         .iter()
-        .any(|style| style.name.eq_ignore_ascii_case("ISO-25"))
+        .find(|style| style.name.eq_ignore_ascii_case("ISO-25"))
     {
-        return;
+        return style.handle;
     }
     let mut style = DimStyle::new("ISO-25");
     style.handle = doc.allocate_handle();
@@ -82,7 +84,9 @@ pub fn ensure_iso_dim_style(doc: &mut CadDocument) {
     style.dimjogang = std::f64::consts::FRAC_PI_2;
     style.dimmzf = 100.0;
     style.dimaltmzf = 100.0;
+    let handle = style.handle;
     let _ = doc.dim_styles.add(style);
+    handle
 }
 
 fn named_dim_style(doc: &CadDocument, name: &str) -> Option<DimStyle> {

src/scene/entity.rs

@@ -2733,8 +2733,11 @@ impl Scene {
         // current. Standard stays available for imperial work.
         self.document.header.measurement = 1;
         self.document.header.insertion_units = 4;
-        crate::scene::creation_style::ensure_iso_dim_style(&mut self.document);
+        let iso = crate::scene::creation_style::ensure_iso_dim_style(&mut self.document);
         self.document.header.current_dimstyle_name = "ISO-25".to_string();
+        // The name alone leaves the header pointing at the previous style, and
+        // a DWG writes the current style by handle only.
+        self.document.header.current_dimstyle_handle = iso;
         for obj in self.document.objects.values_mut() {
             if let acadrust::objects::ObjectType::Layout(l) = obj {
                 if l.name != "Model" {

src/scene/parametric_constraints.rs

@@ -732,8 +732,15 @@ pub(crate) fn dimensional_anchor_refs(
         return Vec::new();
     };
     // A whole circle or arc (a radius or diameter): its center stays and the
-    // value resizes it.
-    if refs.len() == 1 && first.marker.is_none() {
+    // value resizes it. A single whole reference can also be a line's length,
+    // whose start is what stays, so the entity decides.
+    if refs.len() == 1
+        && first.marker.is_none()
+        && matches!(
+            document.get_entity(first.entity),
+            Some(acadrust::EntityType::Circle(_) | acadrust::EntityType::Arc(_))
+        )
+    {
         return vec![ParametricRef::center(first.entity)];
     }
     // Three point references: a three-point angle `[first, vertex, second]`.

src/scene/parametric_solve.rs

@@ -4152,7 +4152,8 @@ mod tests {
         )));
         let refs = [ParametricRef::point(line, 0), ParametricRef::point(line, 1)];
         // A distance keeps a negative value's sign in the parameter and
-        // measures its magnitude (`d1=-50`); a radius has no such reading.
+        // measures its magnitude (`d1=-50`); a radius reads the same way
+        // (`rad1=-20` is a radius of 20), and only zero leaves no circle.
         assert!(scene
             .validate_parametric_constraint(
                 ConstraintKind::Distance,
@@ -4170,6 +4171,13 @@ mod tests {
                 &[ParametricRef::whole(circle)],
                 Some(&DrivingValue::Literal(-1.0)),
             )
+            .is_ok());
+        assert!(scene
+            .validate_parametric_constraint(
+                ConstraintKind::Radius,
+                &[ParametricRef::whole(circle)],
+                Some(&DrivingValue::Literal(0.0)),
+            )
             .is_err());
         assert!(scene
             .validate_parametric_constraint(