[X11] Fixed maximize behavior for transient windows

samples/ControlCatalog/Pages/DialogsPage.xaml

@@ -6,6 +6,7 @@
       <Button Name="SaveFile">Save File</Button>
       <Button Name="SelectFolder">Select Folder</Button>
       <Button Name="DecoratedWindow">Decorated window</Button>
+      <Button Name="DecoratedWindowDialog">Decorated window (dialog)</Button>
       <Button Name="Dialog">Dialog</Button>
   </StackPanel>
 </UserControl>

samples/ControlCatalog/Pages/DialogsPage.xaml.cs

@@ -31,9 +31,13 @@ namespace ControlCatalog.Pages
                 }.ShowAsync(GetWindow());
             };
             this.FindControl<Button>("DecoratedWindow").Click += delegate
-                {
-                    new DecoratedWindow().ShowDialog(GetWindow());
-                };
+            {
+                new DecoratedWindow().Show();
+            };
+            this.FindControl<Button>("DecoratedWindowDialog").Click += delegate
+            {
+                new DecoratedWindow().ShowDialog(GetWindow());
+            };
             this.FindControl<Button>("Dialog").Click += delegate
                 {
                     new MainWindow().ShowDialog(GetWindow());

src/Avalonia.X11/X11PlatformThreading.cs

@@ -176,6 +176,8 @@ namespace Avalonia.X11
 
                 if (cancellationToken.IsCancellationRequested)
                     return;
+                //Flush whatever requests were made to XServer
+                XFlush(_display);
                 epoll_event ev;
                 var len = epoll_wait(_epoll, &ev, 1,
                     nextTick == null ? -1 : Math.Max(1, (int)(nextTick.Value - _clock.Elapsed).TotalMilliseconds));

src/Avalonia.X11/X11Window.cs

@@ -95,6 +95,9 @@ namespace Avalonia.X11
                 _x11.Atoms.WM_DELETE_WINDOW
             };
             XSetWMProtocols(_x11.Display, _handle, protocols, protocols.Length);
+            XChangeProperty(_x11.Display, _handle, _x11.Atoms._NET_WM_WINDOW_TYPE, _x11.Atoms.XA_ATOM,
+                32, PropertyMode.Replace, new[] {_x11.Atoms._NET_WM_WINDOW_TYPE_NORMAL}, 1);
+            
             var feature = (EglGlPlatformFeature)AvaloniaLocator.Current.GetService<IWindowingPlatformGlFeature>();
             var surfaces = new List<object>
             {
@@ -105,7 +108,7 @@ namespace Avalonia.X11
                     new EglGlPlatformSurface((EglDisplay)feature.Display, feature.DeferredContext,
                         new SurfaceInfo(this, _x11.DeferredDisplay, _handle, _renderHandle)));
             Surfaces = surfaces.ToArray();
-            UpdateMotifHits();
+            UpdateMotifHints();
             XFlush(_x11.Display);
         }
 
@@ -141,10 +144,12 @@ namespace Avalonia.X11
             public double Scaling => _window.Scaling;
         }
 
-        void UpdateMotifHits()
+        void UpdateMotifHints()
         {
-            var functions = MotifFunctions.All;
-            var decorations = MotifDecorations.All;
+            var functions = MotifFunctions.Move | MotifFunctions.Close | MotifFunctions.Resize |
+                            MotifFunctions.Minimize | MotifFunctions.Maximize;
+            var decorations = MotifDecorations.Menu | MotifDecorations.Title | MotifDecorations.Border |
+                              MotifDecorations.Maximize | MotifDecorations.Minimize | MotifDecorations.ResizeH;
 
             if (_popup || !_systemDecorations)
             {
@@ -164,7 +169,6 @@ namespace Avalonia.X11
                 functions = new IntPtr((int)functions)
             };
 
-
             XChangeProperty(_x11.Display, _handle,
                 _x11.Atoms._MOTIF_WM_HINTS, _x11.Atoms._MOTIF_WM_HINTS, 32,
                 PropertyMode.Replace, ref hints, 5);
@@ -392,6 +396,8 @@ namespace Avalonia.X11
             get => _lastWindowState;
             set
             {
+                if(_lastWindowState == value)
+                    return;
                 _lastWindowState = value;
                 if (value == WindowState.Minimized)
                 {
@@ -624,7 +630,7 @@ namespace Avalonia.X11
         public void SetSystemDecorations(bool enabled)
         {
             _systemDecorations = enabled;
-            UpdateMotifHits();
+            UpdateMotifHints();
         }
 
 
@@ -652,7 +658,7 @@ namespace Avalonia.X11
         public void CanResize(bool value)
         {
             _canResize = value;
-            UpdateMotifHits();
+            UpdateMotifHints();
         }
 
         public void SetCursor(IPlatformHandle cursor)