Fixed GTK/Cairo render

src/Gtk/Perspex.Cairo/CairoPlatform.cs

@@ -38,7 +38,11 @@ namespace Perspex.Cairo
 
         public IRenderTarget CreateRenderer(IPlatformHandle handle, double width, double height)
         {
-            return new RenderTarget(handle, width, height);
+            if (handle.HandleDescriptor != "GtkWindow")
+                throw new NotSupportedException(string.Format(
+                    "Don't know how to create a Cairo renderer from a '{0}' handle",
+                    handle.HandleDescriptor));
+            return new RenderTarget((Gtk.Window)handle, width, height);
         }
 
         public IRenderTargetBitmapImpl CreateRenderTargetBitmap(int width, int height)

src/Gtk/Perspex.Cairo/RenderTarget.cs

@@ -17,19 +17,18 @@ namespace Perspex.Cairo
     /// </summary>
     public class RenderTarget : IRenderTarget
     {
-        private readonly IPlatformHandle _handle;
         private readonly Surface _surface;
-        private Gdk.Window _window;
+        private Gtk.Window _window;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="RenderTarget"/> class.
         /// </summary>
-        /// <param name="handle">The window handle.</param>
+        /// <param name="window">The window.</param>
         /// <param name="width">The width of the window.</param>
         /// <param name="height">The height of the window.</param>
-        public RenderTarget(IPlatformHandle handle, double width, double height)
+        public RenderTarget(Gtk.Window window, double width, double height)
         {
-            _handle = handle;
+            _window = window;
         }
 
         public RenderTarget(ImageSurface surface)
@@ -56,19 +55,7 @@ namespace Perspex.Cairo
         {
             if(_surface != null)
                 return new DrawingContext(_surface);
-
-            switch (_handle.HandleDescriptor)
-            {
-                case "GdkWindow":
-                    if (_window == null)
-                        _window = new Gdk.Window(_handle.Handle);
-
-                    return new DrawingContext(_window);
-                default:
-                    throw new NotSupportedException(string.Format(
-                        "Don't know how to create a Cairo renderer from a '{0}' handle",
-                        _handle.HandleDescriptor));
-            }
+            return new DrawingContext(_window.GdkWindow);
         }
         
         public void Dispose() => _surface?.Dispose();

src/Gtk/Perspex.Gtk/WindowImpl.cs

@@ -14,12 +14,10 @@ namespace Perspex.Gtk
 {
     using Gtk = global::Gtk;
 
-    public class WindowImpl : Gtk.Window, IWindowImpl
+    public class WindowImpl : Gtk.Window, IWindowImpl, IPlatformHandle
     {
         private IInputRoot _inputRoot;
-
-        private IPlatformHandle _windowHandle;
-
+        
         private Size _clientSize;
 
         private Gtk.IMContext _imContext;
@@ -46,7 +44,6 @@ namespace Perspex.Gtk
             Events = EventMask.PointerMotionMask |
               EventMask.ButtonPressMask |
               EventMask.ButtonReleaseMask;
-            _windowHandle = new PlatformHandle(Handle, "GtkWindow");
             _imContext = new Gtk.IMMulticontext();
             _imContext.Commit += ImContext_Commit;
         }
@@ -73,7 +70,8 @@ namespace Perspex.Gtk
             }
         }
 
-        IPlatformHandle ITopLevelImpl.Handle => _windowHandle;
+        IPlatformHandle ITopLevelImpl.Handle => this;
+        public string HandleDescriptor => "GtkWindow";
 
         public Action Activated { get; set; }
 
@@ -94,7 +92,9 @@ namespace Perspex.Gtk
 
         public void Invalidate(Rect rect)
         {
-            base.GdkWindow.InvalidateRect (new Rectangle ((int)rect.X, (int)rect.Y, (int)rect.Width, (int)rect.Height), true);
+            if (base.GdkWindow != null)
+                base.GdkWindow.InvalidateRect(
+                    new Rectangle((int) rect.X, (int) rect.Y, (int) rect.Width, (int) rect.Height), true);
         }
 
         public Point PointToScreen(Point point)

src/Perspex.Application/Application.cs

@@ -177,7 +177,7 @@ namespace Perspex
         /// <param name="platformID">The value of Environment.OSVersion.Platform.</param>
         protected void InitializeSubsystems(int platformID)
         {
-            if (platformID == 4 || platformID == 6)
+            if (true)
             {
                 InitializeSubsystem("Perspex.Cairo");
                 InitializeSubsystem("Perspex.Gtk");

src/Perspex.Controls/Platform/ITopLevelRenderer.cs

@@ -5,6 +5,7 @@ using System.Text;
 using System.Threading.Tasks;
 using Perspex.Platform;
 using Perspex.Rendering;
+using Perspex.Threading;
 
 namespace Perspex.Controls.Platform
 {
@@ -42,7 +43,8 @@ namespace Perspex.Controls.Platform
                 viewport.Resize((int) clientSize.Width, (int) clientSize.Height);
             }));
             resources.Add(queueManager.RenderNeeded.Subscribe(_
-                => topLevel.PlatformImpl.Invalidate(new Rect(topLevel.ClientSize))));
+                =>
+                Dispatcher.UIThread.InvokeAsync(() => topLevel.PlatformImpl.Invalidate(new Rect(topLevel.ClientSize)))));
 
             topLevel.PlatformImpl.Paint = rect =>
             {