Restore region bounds and exact profile measurements after reload

src/app/doc_api.rs

@@ -1244,11 +1244,14 @@ impl DocApiBackend for HostSession<'_> {
 
     fn bounds(&mut self, id: ObjectId) -> ApiResult<Aabb> {
         let handle = obj_to_handle(id);
-        // Lift-on-miss for solids (consistent with volume/centroid); borrow the cache
+        // Lift-on-miss for modeler geometry (consistent with volume/centroid); borrow the cache
         // read-only via with_body (O(1), no B-rep deep clone).
         if matches!(
             self.document().get_entity(handle),
             Some(EntityType::Solid3D(_))
+        ) || matches!(
+            self.document().get_entity(handle),
+            Some(EntityType::Region(region)) if region.acis_data.has_data()
         ) {
             let mut f = |body: &KernelBody| -> ApiResult<Aabb> {
                 let bb = cadkernel::brep::body_bounds(body)

src/entities/solid3d.rs

@@ -260,17 +260,26 @@ fn position_section(prefix: &str, p: &acadrust::types::Vector3) -> PropSection {
     }
 }
 
-/// Approximate a region's enclosed area and boundary perimeter from its
-/// wireframe loops. Perimeter is the total edge length across every wire.
-/// Area accumulates the Newell area vector of each loop (opposite-wound
-/// holes subtract) and halves its magnitude — exact for a single planar
-/// loop, approximate for multi-loop or curved regions. Returns zeros when
-/// there is nothing to measure.
-/// The area and perimeter of a region's boundary wires.
-///
-/// Measured in space rather than in projection: a region need not lie in a
-/// coordinate plane, and flattening it to XY first would report its shadow.
-fn region_area_perimeter(wires: &[acadrust::entities::Wire]) -> (f64, f64) {
+/// Measure decoded planar curves in a unit frame, retaining legacy wire-only input.
+fn region_area_perimeter(region: &Region) -> (f64, f64) {
+    let exact = (|| {
+        let (plane, loops, true) = crate::scene::model::presspull_model::profile_geometry(
+            &EntityType::Region(region.clone()),
+        )? else { return None; };
+        let unit = cadkernel::space::Plane::orthonormal(plane.origin, plane.x_axis, plane.normal()?)?;
+        let transform = cadkernel::geom2d::Transform {
+            origin: unit.project(plane.origin)?.into(),
+            x_axis: unit.project_vector(plane.x_axis)?.into(),
+            y_axis: unit.project_vector(plane.y_axis)?.into(),
+        };
+        let curves = loops.iter().flatten().map(|curve| curve.transformed(&transform))
+            .collect::<Option<Vec<_>>>()?;
+        let area = curves.iter().map(|curve| curve.enclosed_area()).sum::<f64>().abs();
+        let perimeter = curves.iter().map(|curve| curve.length()).sum::<f64>();
+        (area.is_finite() && perimeter.is_finite()).then_some((area, perimeter))
+    })();
+    if let Some(measurements) = exact { return measurements; }
+    let wires = &region.wires;
     let mut area_vector = [0.0f64; 3];
     let mut perimeter = 0.0;
     for wire in wires {
@@ -351,7 +360,7 @@ impl Grippable for Region {
 
 impl PropertyEditable for Region {
     fn geometry_properties(&self, _text_style_names: &[String]) -> Vec<PropSection> {
-        let (area, perimeter) = region_area_perimeter(&self.wires);
+        let (area, perimeter) = region_area_perimeter(self);
         let mut sections =
             acis_sections(&self.acis_data, &self.wires, &self.silhouettes, self.history_handle);
         sections[0]

src/scene/convert/tess.rs

@@ -1719,6 +1719,15 @@ pub(crate) fn set_wire_aabb(w: &mut WireModel, entity_box: [f32; 4]) {
 }
 
 fn entity_bounds(e: &acadrust::EntityType) -> ([f64; 3], [f64; 3]) {
+    if let acadrust::EntityType::Region(region) = e {
+        if region.wires.is_empty() {
+            if let Some(bounds) = super::solid3d_tess::kernel_region_body(region)
+                .and_then(|body| cadkernel::brep::body_bounds(&body))
+            {
+                return (bounds.min, bounds.max);
+            }
+        }
+    }
     if let acadrust::EntityType::Line(line) = e {
         if let Some(association) = acadrust::entities::CenterMarkAssociation::read(
             &line.common.extended_data,