fixed bug with initial size and position calculation for X11Window (in some cases scaling is not applied until first position change event, and all calculations before it provided wrong values) (#12833)

Co-authored-by: Herman Kirshin <herman.kirshin@jetbrains.com>

src/Avalonia.Controls/Window.cs

@@ -714,6 +714,11 @@ namespace Avalonia.Controls
                 _shown = true;
                 IsVisible = true;
 
+                // We need to set position first because it is required for getting correct display scale. If position is not manual then it can be
+                // determined only by calling this method. But here it will calculate not precise location because scaling may not yet be applied (see i.e. X11Window),
+                // thus we ought to call it again later to center window correctly if needed, when scaling will be already applied
+                SetWindowStartupLocation(owner);
+
                 var initialSize = new Size(
                     double.IsNaN(Width) ? Math.Max(MinWidth, ClientSize.Width) : Width,
                     double.IsNaN(Height) ? Math.Max(MinHeight, ClientSize.Height) : Height);
@@ -727,6 +732,7 @@ namespace Avalonia.Controls
 
                 Owner = owner;
 
+                // Second call will calculate correct position because both current and owner windows have correct scaling.
                 SetWindowStartupLocation(owner);
 
                 StartRendering();
@@ -787,6 +793,11 @@ namespace Avalonia.Controls
                 _showingAsDialog = true;
                 IsVisible = true;
 
+                // We need to set position first because it is required for getting correct display scale. If position is not manual then it can be
+                // determined only by calling this method. But here it will calculate not precise location because scaling may not yet be applied (see i.e. X11Window),
+                // thus we ought to call it again later to center window correctly if needed, when scaling will be already applied
+                SetWindowStartupLocation(owner);
+
                 var initialSize = new Size(
                     double.IsNaN(Width) ? ClientSize.Width : Width,
                     double.IsNaN(Height) ? ClientSize.Height : Height);
@@ -802,6 +813,7 @@ namespace Avalonia.Controls
 
                 Owner = owner;
 
+                // Second call will calculate correct position because both current and owner windows have correct scaling.
                 SetWindowStartupLocation(owner);
 
                 StartRendering();

src/Avalonia.X11/X11Window.cs

@@ -1026,7 +1026,11 @@ namespace Avalonia.X11
 
 
         public void Resize(Size clientSize, WindowResizeReason reason) => Resize(clientSize, false, reason);
-        public void Move(PixelPoint point) => Position = point;
+        public void Move(PixelPoint point)
+        {
+            Position = point;
+            UpdateScaling();
+        }
         private void MoveResize(PixelPoint position, Size size, double scaling)
         {
             Move(position);