Fixed unnecessary window displacement on resize (#18004)

* Added new test: changing window size should not change position

* Removed unnecessary window placement assignment to fix window position shifting due to incorrect workspace coordinate usage

* Fixed test because buttons went off the window on tiny screen resolutions

* Make test Windows specific

* Use `Bounds` instead of `Width` and `Height` properties as they are "requested" size rather than actual size (see #18060)

samples/IntegrationTestApp/ShowWindowTest.axaml

@@ -53,7 +53,11 @@
       <Label Grid.Row="11" Content="MeasuredWith:" />
       <TextBlock Grid.Column="1" Grid.Row="11" Name="CurrentMeasuredWithText" Text="{Binding #MyBorder.MeasuredWith}" />
 
-      <Button Name="HideButton" Grid.Row="12" Command="{Binding $parent[Window].Hide}">Hide</Button>
+      <StackPanel Orientation="Horizontal" Grid.Row="12">
+        <Button Name="HideButton" Command="{Binding $parent[Window].Hide}">Hide</Button>
+        <Button Name="AddToWidth" Click="AddToWidth_Click">Add to Width</Button>
+        <Button Name="AddToHeight" Click="AddToHeight_Click">Add to Height</Button>
+      </StackPanel>
       
     </Grid>
   </integrationTestApp:MeasureBorder>

samples/IntegrationTestApp/ShowWindowTest.axaml.cs

@@ -2,6 +2,7 @@ using System;
 using System.Runtime.InteropServices;
 using Avalonia;
 using Avalonia.Controls;
+using Avalonia.Interactivity;
 using Avalonia.Threading;
 
 namespace IntegrationTestApp
@@ -70,5 +71,8 @@ namespace IntegrationTestApp
         {
             _orderTextBox!.Text = MacOSIntegration.GetOrderedIndex(this).ToString();
         }
+
+        private void AddToWidth_Click(object? sender, RoutedEventArgs e) => Width = Bounds.Width + 10;
+        private void AddToHeight_Click(object? sender, RoutedEventArgs e) => Height = Bounds.Height + 10;
     }
 }

src/Windows/Avalonia.Win32/WindowImpl.cs

@@ -608,12 +608,6 @@ namespace Avalonia.Win32
                     return;
                 }
             }
-            else
-            {
-                var position = Position;
-                windowPlacement.NormalPosition.left = position.X;
-                windowPlacement.NormalPosition.top = position.Y;
-            }
 
             windowPlacement.NormalPosition.right = windowPlacement.NormalPosition.left + windowWidth;
             windowPlacement.NormalPosition.bottom = windowPlacement.NormalPosition.top + windowHeight;

tests/Avalonia.IntegrationTests.Appium/WindowTests.cs

@@ -349,6 +349,24 @@ namespace Avalonia.IntegrationTests.Appium
             }
         }
 
+        [PlatformFact(TestPlatforms.Windows)]
+        public void Changing_Size_Should_Not_Change_Position()
+        {
+            using (OpenWindow())
+            {
+                var info = GetWindowInfo();
+
+                Session.FindElementByAccessibilityId("AddToWidth").SendClick();
+                Session.FindElementByAccessibilityId("AddToHeight").SendClick();
+
+                var updatedInfo = GetWindowInfo();
+                Assert.Equal(info.Position, updatedInfo.Position);
+                Assert.Equal(info.FrameSize
+                    .WithWidth(info.FrameSize.Width + 10)
+                    .WithHeight(info.FrameSize.Height + 10), updatedInfo.FrameSize);
+            }
+        }
+
         public static TheoryData<Size?, ShowWindowMode, WindowStartupLocation, bool> StartupLocationData()
         {
             var sizes = new Size?[] { null, new Size(400, 300) };