fix: collapse shadow padding when window touches a screen edge

src/Views/ChromelessWindow.cs

@@ -26,6 +26,8 @@ public ChromelessWindow()
         {
             Focusable = true;
             Native.OS.SetupForWindow(this);
+            PositionChanged += (_, _) => UpdateEdgeSnapInsets();
+            Resized += (_, _) => UpdateEdgeSnapInsets();
         }
 
         public void BeginMoveWindow(object _, PointerPressedEventArgs e)
@@ -89,6 +91,9 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
 
             if (OperatingSystem.IsWindows() && change.Property == WindowStateProperty)
                 Native.Win64Utilities.FixWindowFrame(this);
+
+            if (change.Property == WindowStateProperty)
+                UpdateEdgeSnapInsets();
         }
 
         protected override void OnKeyDown(KeyEventArgs e)
@@ -132,5 +137,47 @@ private void OnWindowBorderPointerPressed(object sender, PointerPressedEventArgs
             if (sender is Border { Tag: WindowEdge edge } && CanResize)
                 BeginResizeDrag(edge, e);
         }
+
+        // The transparent padding around the window holds the self-drawn shadow
+        // (keep the value in sync with "Window.custom_window_frame" style).
+        // Collapse it on the side touching a screen edge so the content sits flush.
+        private void UpdateEdgeSnapInsets()
+        {
+            if (!Classes.Contains("custom_window_frame"))
+                return;
+
+            if (WindowState != WindowState.Normal)
+            {
+                // Let the "WindowState=Maximized" style take over
+                ClearValue(PaddingProperty);
+                return;
+            }
+
+            var screen = Screens.ScreenFromWindow(this);
+            if (screen == null)
+                return;
+
+            var workArea = screen.WorkingArea;
+            var right = Position.X + Bounds.Width;
+            var bottom = Position.Y + Bounds.Height;
+
+            const double tolerance = 2.0;
+            var snapTop = Position.Y <= workArea.Y + tolerance;
+            var snapLeft = Position.X <= workArea.X + tolerance;
+            var snapRight = right >= workArea.Right - tolerance;
+            var snapBottom = bottom >= workArea.Bottom - tolerance;
+
+            if (!snapTop && !snapLeft && !snapRight && !snapBottom)
+            {
+                ClearValue(PaddingProperty);
+                return;
+            }
+
+            Padding = new Thickness(
+                snapLeft ? 0 : 12,
+                snapTop ? 0 : 12,
+                snapRight ? 0 : 12,
+                snapBottom ? 0 : 12);
+        }
     }
 }