DOCS: Added PlayerInput.ActionEvent documentation

Packages/com.unity.inputsystem/InputSystem/Plugins/PlayerInput/PlayerInput.cs

@@ -519,6 +519,8 @@ public PlayerNotifications notificationBehavior
         /// <remarks>
         /// This array is only used if <see cref="notificationBehavior"/> is set to
         /// <see cref="UnityEngine.InputSystem.PlayerNotifications.InvokeUnityEvents"/>.
+        ///
+        /// The list of actions will be dependent on the <see cref="InputActionAsset"/> specified in the <see cref="PlayerInput"/> Editor UI.
         /// </remarks>
         public ReadOnlyArray<ActionEvent> actionEvents
         {
@@ -783,7 +785,7 @@ public ReadOnlyArray<InputDevice> devices
         /// </summary>
         /// <value>True if the player is missing devices required by the control scheme.</value>
         /// <remarks>
-        /// This can happen, for example, if the a device is unplugged during the game.
+        /// This can happen, for example, if a device is unplugged during the game.
         /// </remarks>
         /// <seealso cref="InputControlScheme.deviceRequirements"/>
         /// <seealso cref="InputUser.hasMissingRequiredDevices"/>
@@ -1978,19 +1980,67 @@ private void SwitchControlSchemeInternal(ref InputControlScheme controlScheme, p
             }
         }
 
+        /// <summary>
+        /// An event associated with an PlayerInput action.
+        /// </summary>
+        /// <remarks>
+        /// Represents an event invoked in response to actions being triggered.
+        ///
+        /// Contains the ID and name of the <see cref="InputAction"/> being triggered and the associated <see cref="UnityAction"/> to handle the action response.
+        ///
+        /// The list of action events is specified in <see cref="PlayerInput"/> Editor UI based on the selected <see cref="InputActionAsset"/>.
+        /// The individual action callbacks are then specified in a <see cref="MonoBehaviour"/>.
+        ///
+        /// <example>
+        /// <code>
+        /// public class MyPlayerScript : MonoBehaviour
+        /// {
+        ///     void OnFireEvent(InputAction.CallbackContext context)
+        ///     {
+        ///         // Handle fire event
+        ///     }
+        /// }
+        /// </code>
+        /// </example>
+        /// </remarks>
+        /// <seealso cref="PlayerInput.actionEvents"/>
         [Serializable]
         public class ActionEvent : UnityEvent<InputAction.CallbackContext>
         {
+            /// <summary>
+            /// Action GUID string for the action that triggered the event.
+            /// </summary>
             public string actionId => m_ActionId;
+
+            /// <summary>
+            /// Name of the action that triggered the event.
+            /// </summary>
             public string actionName => m_ActionName;
 
             [SerializeField] private string m_ActionId;
             [SerializeField] private string m_ActionName;
 
+            /// <summary>
+            /// Construct an empty action event.
+            /// </summary>
+            /// <remarks>
+            /// The event will not have an associated action.
+            /// </remarks>
+            /// <seealso cref="PlayerInput.actionEvents"/>
             public ActionEvent()
             {
             }
 
+            /// <summary>
+            /// Construct an action event and associate it with an action.
+            /// </summary>
+            /// <remarks>
+            /// The event will be associated with the specified action. The action must be part of an action asset.
+            /// </remarks>
+            /// <param name="action">The action to associate with the event. The action must be part of an action asset.</param>
+            /// <exception cref="ArgumentNullException">The action is <c>null</c>.</exception>
+            /// <exception cref="ArgumentException">The action is not part of an action asset.</exception>
+            /// <seealso cref="PlayerInput.actionEvents"/>
             public ActionEvent(InputAction action)
             {
                 if (action == null)
@@ -2004,6 +2054,15 @@ public ActionEvent(InputAction action)
                 m_ActionName = $"{action.actionMap.name}/{action.name}";
             }
 
+            /// <summary>
+            /// Construct an action event and associated it with an action by GUID.
+            /// </summary>
+            /// <remarks>
+            /// The event will be associated with the specified action.
+            /// </remarks>
+            /// <param name="actionGUID">Action GUID</param>
+            /// <param name="name">Name of the action</param>
+            /// <seealso cref="PlayerInput.actionEvents"/>
             public ActionEvent(Guid actionGUID, string name = null)
             {
                 m_ActionId = actionGUID.ToString();