refactor: DRY/factor out BendShape::render_discretization

crates/topola-egui/src/painter.rs

@@ -36,26 +36,15 @@ impl<'a> Painter<'a> {
                 ],
                 egui::Stroke::new(seg.width as f32 * self.transform.scaling, color),
             ),
-            PrimitiveShape::Bend(bend) => {
-                let circle = bend.circle();
-
-                let angle_from = bend.start_angle();
-                let angle_step = bend.spanned_angle() / 100.0;
-
-                let points = (0..=100)
-                    .into_iter()
-                    .map(|i| circle.position_at_angle(angle_from + i as f64 * angle_step))
+            PrimitiveShape::Bend(bend) => egui::Shape::line(
+                bend.render_discretization(101)
                     .map(|point| {
                         self.transform
                             .mul_pos([point.0.x as f32, -point.0.y as f32].into())
                     })
-                    .collect();
-
-                egui::Shape::line(
-                    points,
-                    egui::Stroke::new(bend.width as f32 * self.transform.scaling, color),
-                )
-            }
+                    .collect(),
+                egui::Stroke::new(bend.width as f32 * self.transform.scaling, color),
+            ),
         };
 
         self.ui.painter().add(epaint_shape);

src/geometry/primitive.rs

@@ -296,6 +296,16 @@ impl BendShape {
             angle
         }
     }
+
+    /// Render this bend as a list of points on its circle.
+    pub fn render_discretization(&self, point_count: usize) -> impl Iterator<Item = Point> + '_ {
+        let circle = self.circle();
+        let angle_from = self.start_angle();
+        // we need to use one less than the whole point count
+        // because we need to also emit the end-point
+        let angle_step = self.spanned_angle() / ((point_count - 1) as f64);
+        (0..point_count).map(move |i| circle.position_at_angle(angle_from + i as f64 * angle_step))
+    }
 }
 
 impl MeasureLength for BendShape {

src/specctra/design.rs

@@ -94,19 +94,9 @@ impl SpecctraDesign {
                         // line segments.
                         // TODO: make this configurable? pick a smarter value?
                         let segment_count: usize = 100;
-
-                        let circle = bend.circle();
-                        let angle_from = bend.start_angle();
-                        let angle_step = bend.spanned_angle() / segment_count as f64;
-
-                        (0..=segment_count)
-                            .into_iter()
-                            .map(|i| {
-                                circle
-                                    .position_at_angle(angle_from + i as f64 * angle_step)
-                                    .into()
-                            })
-                            .collect::<Vec<structure::Point>>()
+                        bend.render_discretization(segment_count + 1)
+                            .map(Into::into)
+                            .collect()
                     }
 
                     // Intentionally skipped for now.