From 93e5e6d27ed2efb5b4f6fed453645e42c3920113 Mon Sep 17 00:00:00 2001
From: Shane Celis <shane.celis@gmail.com>
Date: Sat, 21 Sep 2024 21:33:02 -0400
Subject: [PATCH] feature: Add From impls for DistanceLimit.

Add From<Scalar> and From<(Scalar, Scalar)> for DistanceLimit.
---
 crates/avian2d/examples/distance_joint_2d.rs |  2 +-
 crates/avian3d/examples/distance_joint_3d.rs |  2 +-
 src/dynamics/solver/joints/distance.rs       | 32 +++++++++++++-------
 src/dynamics/solver/joints/mod.rs            | 20 ++++++++++++
 4 files changed, 43 insertions(+), 13 deletions(-)

diff --git a/crates/avian2d/examples/distance_joint_2d.rs b/crates/avian2d/examples/distance_joint_2d.rs
index 77aa85d0..f2bde85b 100644
--- a/crates/avian2d/examples/distance_joint_2d.rs
+++ b/crates/avian2d/examples/distance_joint_2d.rs
@@ -51,7 +51,7 @@ fn setup(mut commands: Commands) {
         DistanceJoint::new(anchor, object)
             .with_local_anchor_1(Vector::ZERO)
             .with_local_anchor_2(Vector::ZERO)
-            .with_rest_length(100.0)
+            .with_length_limits(100.0)
             .with_linear_velocity_damping(0.1)
             .with_angular_velocity_damping(1.0)
             .with_compliance(0.00000001),
diff --git a/crates/avian3d/examples/distance_joint_3d.rs b/crates/avian3d/examples/distance_joint_3d.rs
index 8a617960..594654f2 100644
--- a/crates/avian3d/examples/distance_joint_3d.rs
+++ b/crates/avian3d/examples/distance_joint_3d.rs
@@ -52,7 +52,7 @@ fn setup(
     commands.spawn(
         DistanceJoint::new(static_cube, dynamic_cube)
             .with_local_anchor_2(0.5 * Vector::ONE)
-            .with_rest_length(1.5)
+            .with_length_limits(1.5)
             .with_compliance(1.0 / 400.0),
     );
 
diff --git a/src/dynamics/solver/joints/distance.rs b/src/dynamics/solver/joints/distance.rs
index 665af1e0..4c5ad52a 100644
--- a/src/dynamics/solver/joints/distance.rs
+++ b/src/dynamics/solver/joints/distance.rs
@@ -167,22 +167,32 @@ impl DistanceJoint {
         self.compute_force(self.lagrange, dir, dt)
     }
 
-    /// Sets the minimum and maximum distances between the attached bodies.
-    pub fn with_limits(self, min: Scalar, max: Scalar) -> Self {
+    /// Returns self with the minimum and maximum distances between the attached
+    /// bodies.
+    ///
+    /// ``
+    /// # #[cfg(feature = "2d")]
+    /// # use avian2d::prelude::*;
+    /// # #[cfg(feature = "3d")]
+    /// # use avian3d::prelude::*;
+    /// # use bevy::perlude::*;`
+    /// # fn new_joint() -> DistanceJoint { DistanceJoint::new(Entity::PLACEHOLDER, Entity::PLACEHOLDER) }
+    /// let j: DistanceJoint = new_joint();
+    /// let a = j.with_length_limits(DistanceLimit { min: 0.0, max: 1.0 });
+    /// let b = j.with_length_limits((0.0, 1.0));
+    /// assert_eq!(a, b);
+    ///
+    /// let c = j.with_length_limits(DistanceLimit { min: 0.5, max: 0.5 });
+    /// let d = j.with_length_limits(0.5);
+    /// assert_eq!(c, d);
+    /// ```
+    pub fn with_length_limits(self, limit: impl Into<DistanceLimit>) -> Self {
         Self {
-            length_limits: DistanceLimit::new(min, max),
+            length_limits: limit.into(),
             ..self
         }
     }
 
-    /// Sets the joint's minimum and maximum length limit to `rest_length`, or
-    /// distance the bodies will be kept at.
-    pub fn with_rest_length(self, rest_length: Scalar) -> Self {
-        Self {
-            length_limits: DistanceLimit::new(rest_length, rest_length),
-            ..self
-        }
-    }
 }
 
 impl PositionConstraint for DistanceJoint {}
diff --git a/src/dynamics/solver/joints/mod.rs b/src/dynamics/solver/joints/mod.rs
index 6fa37350..b0cfb396 100644
--- a/src/dynamics/solver/joints/mod.rs
+++ b/src/dynamics/solver/joints/mod.rs
@@ -194,6 +194,26 @@ pub struct DistanceLimit {
     pub max: Scalar,
 }
 
+/// Convert the `limit` into a distance limit where _min = max = limit_.
+impl From<Scalar> for DistanceLimit {
+    fn from(limit: Scalar) -> DistanceLimit {
+        DistanceLimit {
+            min: limit,
+            max: limit
+        }
+    }
+}
+
+/// Convert the `(min, max)` pair into a distance limit.
+impl From<(Scalar, Scalar)> for DistanceLimit {
+    fn from((min, max): (Scalar, Scalar)) -> DistanceLimit {
+        DistanceLimit {
+            min,
+            max
+        }
+    }
+}
+
 impl DistanceLimit {
     /// A `DistanceLimit` with `min` and `max` set to zero.
     pub const ZERO: Self = Self { min: 0.0, max: 0.0 };