Use Hint/Actual naming

src/Avalonia.Controls/Embedding/Offscreen/OffscreenTopLevelImpl.cs

@@ -65,7 +65,7 @@ namespace Avalonia.Controls.Embedding.Offscreen
         public Action Closed { get; set; }
         public abstract IMouseDevice MouseDevice { get; }
 
-        public WindowTransparencyLevel TransparencyLevel { get => WindowTransparencyLevel.None; set { } }
+        public WindowTransparencyLevel TransparencyLevelHint { get => WindowTransparencyLevel.None; set { } }
 
         public IPopupImpl CreatePopup() => null;
     }

src/Avalonia.Controls/Platform/ITopLevelImpl.cs

@@ -59,6 +59,9 @@ namespace Avalonia.Platform
         /// </summary>
         Action<double> ScalingChanged { get; set; }
 
+        /// <summary>
+        /// Gets or sets a method called when the toplevel's TransparencyLevel changes.
+        /// </summary>
         Action<WindowTransparencyLevel> TransparencyLevelChanged { get; set; }
 
         /// <summary>
@@ -111,8 +114,8 @@ namespace Avalonia.Platform
         IPopupImpl CreatePopup();
 
         /// <summary>
-        /// Gets or sets the <see cref="WindowTransparencyLevel"/> ofthe TopLevel.
+        /// Gets or sets the <see cref="WindowTransparencyLevel"/> of the TopLevel.
         /// </summary>
-        WindowTransparencyLevel TransparencyLevel { get; set; }
+        WindowTransparencyLevel TransparencyLevelHint { get; set; }
     }
 }

src/Avalonia.Controls/TopLevel.cs

@@ -83,7 +83,7 @@ namespace Avalonia.Controls
             AffectsMeasure<TopLevel>(ClientSizeProperty);
 
             TransparencyLevelHintProperty.Changed.AddClassHandler<TopLevel>(
-                (tl, e) => { if (tl.PlatformImpl != null) tl.PlatformImpl.TransparencyLevel = (WindowTransparencyLevel)e.NewValue; });
+                (tl, e) => { if (tl.PlatformImpl != null) tl.PlatformImpl.TransparencyLevelHint = (WindowTransparencyLevel)e.NewValue; });
         }
 
         /// <summary>
@@ -402,7 +402,7 @@ namespace Avalonia.Controls
 
             _transparencyFallbackBorder = e.NameScope.Find<Border>("PART_TransparencyFallback");
 
-            HandleTransparencyLevelChanged(PlatformImpl.TransparencyLevel);
+            HandleTransparencyLevelChanged(PlatformImpl.TransparencyLevelHint);
         }
 
         /// <summary>

src/Avalonia.DesignerSupport/Remote/Stubs.cs

@@ -144,7 +144,7 @@ namespace Avalonia.DesignerSupport.Remote
 
         public Action GotInputWhenDisabled { get; set; }
 
-        public WindowTransparencyLevel TransparencyLevel { get => WindowTransparencyLevel.None; set { } }
+        public WindowTransparencyLevel TransparencyLevelHint { get => WindowTransparencyLevel.None; set { } }
     }
 
     class ClipboardStub : IClipboard

src/Avalonia.Native/WindowImplBase.cs

@@ -393,7 +393,7 @@ namespace Avalonia.Native
 
         private WindowTransparencyLevel _transparencyLevel;
 
-        public WindowTransparencyLevel TransparencyLevel 
+        public WindowTransparencyLevel TransparencyLevelHint 
         {
             get => _transparencyLevel;
             set

src/Avalonia.X11/X11Window.cs

@@ -1086,6 +1086,6 @@ namespace Avalonia.X11
 
         public IPopupPositioner PopupPositioner { get; }
         public ITopLevelNativeMenuExporter NativeMenuExporter { get; }
-        public WindowTransparencyLevel TransparencyLevel { get; set; }
+        public WindowTransparencyLevel TransparencyLevelHint { get; set; }
     }
 }

src/Linux/Avalonia.LinuxFramebuffer/FramebufferToplevelImpl.cs

@@ -83,6 +83,6 @@ namespace Avalonia.LinuxFramebuffer
 
         public Size ScaledSize => _outputBackend.PixelSize.ToSize(Scaling);
 
-        public WindowTransparencyLevel TransparencyLevel { get => WindowTransparencyLevel.None; set { } }
+        public WindowTransparencyLevel TransparencyLevelHint { get => WindowTransparencyLevel.None; set { } }
     }
 }

src/Windows/Avalonia.Win32/WindowImpl.cs

@@ -210,7 +210,7 @@ namespace Avalonia.Win32
             }
         }
 
-        public WindowTransparencyLevel TransparencyLevel
+        public WindowTransparencyLevel TransparencyLevelHint
         {
             get => _transparencyLevel;
             set