Match ordered tangent constraint behavior

src/modules/parametric/mod.rs

@@ -5,6 +5,7 @@
 mod coincident;
 mod equal_distance;
 mod point_on_entity;
+mod tangent;
 mod tools;
 mod value;
 pub use coincident::{coincident_tool, CoincidentConstraintCommand};
@@ -12,6 +13,7 @@ pub use equal_distance::{equal_distance_tool, EqualDistanceConstraintCommand};
 pub use point_on_entity::{
     center_point_tool, midpoint_tool, point_on_curve_tool, PointOnEntityConstraintCommand,
 };
+pub use tangent::TangentConstraintCommand;
 pub use tools::{
     colinear, concentric, equal, fixed, horizontal, normal, parallel, perpendicular, symmetric,
     tangent, vertical,

src/modules/parametric/tangent.rs

@@ -0,0 +1,168 @@
+use acadrust::{EntityType, Handle};
+use glam::DVec3;
+
+use crate::command::{CadCommand, CmdResult};
+use crate::scene::parametric_constraints::ParametricRef;
+use crate::t;
+
+#[derive(Clone, Copy, PartialEq, Eq)]
+enum TangentOperand {
+    Line,
+    Circle,
+    Ellipse,
+}
+
+#[derive(Clone, Copy)]
+struct TangentPick {
+    reference: ParametricRef,
+    operand: TangentOperand,
+}
+
+pub struct TangentConstraintCommand {
+    first: Option<TangentPick>,
+    picked_entity: Option<EntityType>,
+}
+
+impl TangentConstraintCommand {
+    pub fn new() -> Self {
+        Self {
+            first: None,
+            picked_entity: None,
+        }
+    }
+
+    fn invalid_selection() -> CmdResult {
+        CmdResult::ReportError(
+            t!("Invalid selection for Tangent. Select a line, polyline segment, circle, arc or ellipse.")
+                .into_owned(),
+        )
+    }
+
+    fn picked_reference(entity: &EntityType, handle: Handle, point: DVec3) -> Option<TangentPick> {
+        let (reference, operand) = match entity {
+            EntityType::Line(_) => (ParametricRef::whole(handle), TangentOperand::Line),
+            EntityType::Circle(_) | EntityType::Arc(_) => {
+                (ParametricRef::whole(handle), TangentOperand::Circle)
+            }
+            EntityType::Ellipse(_) => (ParametricRef::whole(handle), TangentOperand::Ellipse),
+            EntityType::LwPolyline(_) | EntityType::Polyline2D(_) => {
+                let (source, _, _) = crate::scene::centerline::picked_source(entity, handle, point)?;
+                let index = usize::try_from(source.segment_index).ok()?;
+                (ParametricRef::segment(handle, index), TangentOperand::Line)
+            }
+            _ => return None,
+        };
+        Some(TangentPick { reference, operand })
+    }
+
+    fn pair_supported(first: TangentOperand, second: TangentOperand) -> bool {
+        matches!(
+            (first, second),
+            (TangentOperand::Circle, TangentOperand::Circle)
+                | (TangentOperand::Circle, TangentOperand::Line)
+                | (TangentOperand::Line, TangentOperand::Circle)
+                | (TangentOperand::Ellipse, TangentOperand::Line)
+                | (TangentOperand::Line, TangentOperand::Ellipse)
+        )
+    }
+
+    pub fn preselected_reference(
+        entity: &EntityType,
+        handle: Handle,
+    ) -> Option<ParametricRef> {
+        match entity {
+            EntityType::Line(_)
+            | EntityType::Circle(_)
+            | EntityType::Arc(_)
+            | EntityType::Ellipse(_) => Some(ParametricRef::whole(handle)),
+            EntityType::LwPolyline(polyline) => {
+                let segments = if polyline.is_closed {
+                    polyline.vertices.len()
+                } else {
+                    polyline.vertices.len().saturating_sub(1)
+                };
+                (segments == 1 && polyline.vertices.first()?.bulge.abs() <= 1.0e-12)
+                    .then(|| ParametricRef::segment(handle, 0))
+            }
+            EntityType::Polyline2D(polyline) => {
+                let segments = if polyline.is_closed() {
+                    polyline.vertices.len()
+                } else {
+                    polyline.vertices.len().saturating_sub(1)
+                };
+                (segments == 1 && polyline.vertices.first()?.bulge.abs() <= 1.0e-12)
+                    .then(|| ParametricRef::segment(handle, 0))
+            }
+            _ => None,
+        }
+    }
+}
+
+impl CadCommand for TangentConstraintCommand {
+    fn name(&self) -> &'static str {
+        "TCONSTRAINT"
+    }
+
+    fn prompt(&self) -> String {
+        if self.first.is_some() {
+            t!("TCONSTRAINT  Select second object:").into_owned()
+        } else {
+            t!("TCONSTRAINT  Select first object:").into_owned()
+        }
+    }
+
+    fn needs_entity_pick(&self) -> bool {
+        true
+    }
+
+    fn entity_pick_highlights_hover(&self) -> bool {
+        true
+    }
+
+    fn inject_before_entity_pick(&self) -> bool {
+        true
+    }
+
+    fn inject_picked_entity(&mut self, entity: EntityType) {
+        self.picked_entity = Some(entity);
+    }
+
+    fn on_entity_pick(&mut self, handle: Handle, point: DVec3) -> CmdResult {
+        if handle.is_null() {
+            return CmdResult::NeedPoint;
+        }
+        let Some(entity) = self.picked_entity.take() else {
+            return CmdResult::NeedPoint;
+        };
+        let Some(pick) = Self::picked_reference(&entity, handle, point) else {
+            return Self::invalid_selection();
+        };
+        let Some(first) = self.first else {
+            self.first = Some(pick);
+            return CmdResult::NeedPoint;
+        };
+        if first.reference == pick.reference
+            || !Self::pair_supported(first.operand, pick.operand)
+        {
+            return Self::invalid_selection();
+        }
+        CmdResult::AddTangentConstraint {
+            first: first.reference,
+            second: pick.reference,
+            label: "Tangent constraint",
+        }
+    }
+
+    fn on_point(&mut self, _point: DVec3) -> CmdResult {
+        CmdResult::NeedPoint
+    }
+
+    fn on_enter(&mut self) -> CmdResult {
+        CmdResult::Cancel
+    }
+
+    fn on_escape(&mut self) -> CmdResult {
+        CmdResult::Cancel
+    }
+}
+