Add RoutedEventRegistry. Fixes #1846.

src/Avalonia.Interactivity/RoutedEvent.cs

@@ -72,7 +72,9 @@ namespace Avalonia.Interactivity
         {
             Contract.Requires<ArgumentNullException>(name != null);
 
-            return new RoutedEvent<TEventArgs>(name, routingStrategy, typeof(TOwner));
+            var routedEvent = new RoutedEvent<TEventArgs>(name, routingStrategy, typeof(TOwner));
+            RoutedEventRegistry.Instance.Register(typeof(TOwner), routedEvent);
+            return routedEvent;
         }
 
         public static RoutedEvent<TEventArgs> Register<TEventArgs>(
@@ -83,7 +85,9 @@ namespace Avalonia.Interactivity
         {
             Contract.Requires<ArgumentNullException>(name != null);
 
-            return new RoutedEvent<TEventArgs>(name, routingStrategy, ownerType);
+            var routedEvent = new RoutedEvent<TEventArgs>(name, routingStrategy, ownerType);
+            RoutedEventRegistry.Instance.Register(ownerType, routedEvent);
+            return routedEvent;
         }
 
         public IDisposable AddClassHandler(

src/Avalonia.Interactivity/RoutedEventRegistry.cs

@@ -0,0 +1,90 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System;
+using System.Collections.Generic;
+
+namespace Avalonia.Interactivity
+{
+    /// <summary>
+    /// Tracks registered <see cref="RoutedEvent"/>s.
+    /// </summary>
+    public class RoutedEventRegistry
+    {
+        private readonly Dictionary<Type, List<RoutedEvent>> _registeredRoutedEvents =
+            new Dictionary<Type, List<RoutedEvent>>();
+
+        /// <summary>
+        /// Gets the <see cref="RoutedEventRegistry"/> instance.
+        /// </summary>
+        public static RoutedEventRegistry Instance { get; }
+            = new RoutedEventRegistry();
+
+        /// <summary>
+        /// Registers a <see cref="RoutedEvent"/> on a type.
+        /// </summary>
+        /// <param name="type">The type.</param>
+        /// <param name="event">The event.</param>
+        /// <remarks>
+        /// You won't usually want to call this method directly, instead use the
+        /// <see cref="RoutedEvent.Register{TOwner, TEventArgs}(string, RoutingStrategies)"/>
+        /// method.
+        /// </remarks>
+        public void Register(Type type, RoutedEvent @event)
+        {
+            Contract.Requires<ArgumentNullException>(type != null);
+            Contract.Requires<ArgumentNullException>(@event != null);
+
+            if (!_registeredRoutedEvents.TryGetValue(type, out var list))
+            {
+                list = new List<RoutedEvent>();
+                _registeredRoutedEvents.Add(type, list);
+            }
+            list.Add(@event);
+        }
+
+        /// <summary>
+        /// Returns all routed events, that are currently registered in the event registry.
+        /// </summary>
+        /// <returns>All routed events, that are currently registered in the event registry.</returns>
+        public IEnumerable<RoutedEvent> GetAllRegistered()
+        {
+            foreach (var events in _registeredRoutedEvents.Values)
+            {
+                foreach (var e in events)
+                {
+                    yield return e;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Returns all routed events registered with the provided type.
+        /// If the type is not found or does not provide any routed events, an empty list is returned.
+        /// </summary>
+        /// <param name="type">The type.</param>
+        /// <returns>All routed events registered with the provided type.</returns>
+        public IReadOnlyList<RoutedEvent> GetRegistered(Type type)
+        {
+            Contract.Requires<ArgumentNullException>(type != null);
+
+            if (_registeredRoutedEvents.TryGetValue(type, out var events))
+            {
+                return events;
+            }
+
+            return Array.Empty<RoutedEvent>();
+        }
+
+        /// <summary>
+        /// Returns all routed events registered with the provided type.         
+        /// If the type is not found or does not provide any routed events, an empty list is returned.
+        /// </summary>
+        /// <typeparam name="TOwner">The type.</typeparam>
+        /// <returns>All routed events registered with the provided type.</returns>
+        public IReadOnlyList<RoutedEvent> GetRegistered<TOwner>()
+        {
+            return GetRegistered(typeof(TOwner));
+        }
+    }
+}

tests/Avalonia.Interactivity.UnitTests/RoutedEventRegistryTests.cs

@@ -0,0 +1,49 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System.Collections.Generic;
+using Avalonia.Controls;
+using Avalonia.Input;
+using Xunit;
+
+namespace Avalonia.Interactivity.UnitTests
+{
+    public class RoutedEventRegistryTests
+    {
+        [Fact]
+        public void Pointer_Events_Should_Be_Registered()
+        {
+            var expectedEvents = new List<RoutedEvent> { InputElement.PointerPressedEvent, InputElement.PointerReleasedEvent }; 
+            var registeredEvents = RoutedEventRegistry.Instance.GetRegistered<InputElement>();
+            Assert.Contains(registeredEvents, expectedEvents.Contains);
+        }
+
+        [Fact]
+        public void ClickEvent_Should_Be_Registered_On_Button()
+        {
+            var expectedEvents = new List<RoutedEvent> { Button.ClickEvent };
+            var registeredEvents = RoutedEventRegistry.Instance.GetRegistered<Button>();
+            Assert.Contains(registeredEvents, expectedEvents.Contains);
+        }
+
+        [Fact]
+        public void ClickEvent_Should_Not_Be_Registered_On_ContentControl()
+        {
+            // force ContentControl type to be loaded
+            new ContentControl();
+            var expectedEvents = new List<RoutedEvent> { Button.ClickEvent };
+            var registeredEvents = RoutedEventRegistry.Instance.GetRegistered<ContentControl>();
+            Assert.DoesNotContain(registeredEvents, expectedEvents.Contains);
+        }
+
+        [Fact]
+        public void InputElement_Events_Should_Not_Be_Registered_On_Button()
+        {
+            // force Button type to be loaded
+            new Button();
+            var expectedEvents = new List<RoutedEvent> { InputElement.PointerPressedEvent, InputElement.PointerReleasedEvent };
+            var registeredEvents = RoutedEventRegistry.Instance.GetRegistered<Button>();
+            Assert.DoesNotContain(registeredEvents, expectedEvents.Contains);
+        }
+    }
+}