Fix segfault on Linux related to EventsLoopProxy. Implement OS window button close

src/Avalonia.Windowing/Bindings/EventNotifier.cs

@@ -10,6 +10,7 @@ namespace Avalonia.Windowing.Bindings
     public delegate void CharacterEventCallback(WindowId windowId, CharacterEvent characterEvent);
     public delegate void AwakenedEventCallback();
     public delegate byte ShouldExitEventLoopCallback(WindowId windowId);
+    public delegate void CloseRequestedCallback(WindowId windowId);
 
     [StructLayout(LayoutKind.Sequential)]
     public struct EventNotifier
@@ -20,5 +21,6 @@ namespace Avalonia.Windowing.Bindings
         public KeyboardEventCallback OnKeyboardEvent;
         public CharacterEventCallback OnCharacterEvent;
         public ShouldExitEventLoopCallback OnShouldExitEventLoop;
+        public CloseRequestedCallback OnCloseRequested;
     }
 }

src/Avalonia.Windowing/Bindings/EventsLoop.cs

@@ -6,7 +6,10 @@ namespace Avalonia.Windowing.Bindings
     public class EventsLoop : IDisposable
     {
         [DllImport("winit_wrapper")]
-        private static extern IntPtr winit_events_loop_new(out IntPtr eventsLoopProxyHandle);
+        private static extern IntPtr winit_events_loop_new();
+
+        [DllImport("winit_wrapper")]
+        private static extern IntPtr winit_events_loop_proxy_new(IntPtr eventsLoopHandle);
 
         [DllImport("winit_wrapper")]
         private static extern void winit_events_loop_destroy(IntPtr handle);
@@ -19,6 +22,7 @@ namespace Avalonia.Windowing.Bindings
         );
 
         public IntPtr Handle { get; private set;  }
+
         private readonly EventsLoopProxy _eventsLoopProxy;
         private readonly EventNotifier _notifier;
 
@@ -28,11 +32,12 @@ namespace Avalonia.Windowing.Bindings
         public event AwakenedEventCallback OnAwakened;
         public event ResizeEventCallback OnResized;
         public event ShouldExitEventLoopCallback OnShouldExitEventLoop;
+        public event CloseRequestedCallback OnCloseRequested;
 
         public EventsLoop()
         {
-            Handle = winit_events_loop_new(out var elpHandle);
-            _eventsLoopProxy = new EventsLoopProxy(elpHandle); 
+            Handle = winit_events_loop_new();
+            _eventsLoopProxy = new EventsLoopProxy(winit_events_loop_proxy_new(Handle)); 
             _notifier = new EventNotifier()
             {
                 OnMouseEvent = (windowId, mouseEvent) => OnMouseEvent?.Invoke(windowId, mouseEvent),
@@ -40,7 +45,8 @@ namespace Avalonia.Windowing.Bindings
                 OnCharacterEvent = (windowId, characterEvent) => OnCharacterEvent?.Invoke(windowId, characterEvent),
                 OnResized = (windowId, resizeEvent) => OnResized?.Invoke(windowId, resizeEvent),
                 OnAwakened = () => OnAwakened?.Invoke(),
-                OnShouldExitEventLoop = (windowId) => (byte)OnShouldExitEventLoop?.Invoke(windowId)
+                OnShouldExitEventLoop = (windowId) => (byte)OnShouldExitEventLoop?.Invoke(windowId),
+                OnCloseRequested = (windowId) => OnCloseRequested?.Invoke(windowId)
             };
         }
 

src/Avalonia.Windowing/WIndowingPlatform.cs

@@ -44,14 +44,29 @@ namespace Avalonia.Windowing
             _eventsLoop.OnAwakened += _eventsLoop_Awakened;
             _eventsLoop.OnResized += _eventsLoop_Resized;
             _eventsLoop.OnShouldExitEventLoop += _eventsLoop_OnShouldExitEventLoop;
+            _eventsLoop.OnCloseRequested += _eventsLoop_OnCloseRequested;
+
             _windows = new Dictionary<WindowId, WindowImpl>();
         }
 
+        void _eventsLoop_OnCloseRequested(WindowId windowId)
+        {
+            if (_windows.ContainsKey(windowId)) 
+            {
+                if (!_windows[windowId].OnCloseRequested()) 
+                {
+                    _windows[windowId].Dispose();    
+                }
+            }
+        }
+
         byte _eventsLoop_OnShouldExitEventLoop(WindowId windowId)
         {
             if (_windows.ContainsKey(windowId))
+            {
+                _windows[windowId].OnClosed();
                 _windows.Remove(windowId);
-            
+            }
             return _windows.Any() ? (byte)0 : (byte)1;
         }
 

src/Avalonia.Windowing/WindowImpl.cs

@@ -319,5 +319,15 @@ namespace Avalonia.Windowing
                 gpuCtx.ResizeContext(ClientSize.Width, ClientSize.Height);
             }
         }
+
+        public void OnClosed() 
+        {
+            Closed?.Invoke();
+        }
+
+        public bool OnCloseRequested() 
+        {
+            return (bool)Closing?.Invoke();
+        }
     }
 }