Add missing comments.

src/geometry/broad_phase_multi_sap/broad_phase_pair_event.rs

@@ -2,12 +2,16 @@ use crate::geometry::ColliderHandle;
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
 #[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+/// A pair of collider handles.
 pub struct ColliderPair {
+    /// The handle of the first collider involved in this pair.
     pub collider1: ColliderHandle,
+    /// The handle of the second ocllider involved in this pair.
     pub collider2: ColliderHandle,
 }
 
 impl ColliderPair {
+    /// Creates a new pair of collider handles.
     pub fn new(collider1: ColliderHandle, collider2: ColliderHandle) -> Self {
         ColliderPair {
             collider1,
@@ -15,10 +19,12 @@ impl ColliderPair {
         }
     }
 
+    /// Swaps the two collider handles in `self`.
     pub fn swap(self) -> Self {
         Self::new(self.collider2, self.collider1)
     }
 
+    /// Constructs a pair of artificial handles that are not guaranteed to be valid..
     pub fn zero() -> Self {
         Self {
             collider1: ColliderHandle::from_raw_parts(0, 0),
@@ -27,7 +33,10 @@ impl ColliderPair {
     }
 }
 
+/// An event emitted by the broad-phase.
 pub enum BroadPhasePairEvent {
+    /// A potential new collision pair has been detected by the broad-phase.
     AddPair(ColliderPair),
+    /// The two colliders are guaranteed not to touch any more.
     DeletePair(ColliderPair),
 }