Keep the clock above the taskbar after the shell raises itself

DesktopClock/MainWindow.xaml.cs

@@ -224,6 +224,8 @@ private void SystemClockTimer_SecondChanged(object sender, EventArgs e)
     {
         UpdateTimeString();
 
+        TryReassertTopmost();
+
         TryShiftPixels();
 
         TryPlaySound();
@@ -271,6 +273,21 @@ private void TryPlaySound()
         }
     }
 
+    /// <summary>
+    /// Puts the clock back above the taskbar, which buries it whenever the shell raises itself.
+    /// </summary>
+    /// <remarks>
+    /// Checking every second rather than reacting to a foreground event is deliberate: the shell also raises itself without changing the foreground, as an auto-hide taskbar does, and reasserting mid-switch gets undone anyway.
+    /// </remarks>
+    private void TryReassertTopmost()
+    {
+        Dispatcher.Invoke(() =>
+        {
+            if (Settings.Default.Topmost && IsVisible && WindowState != WindowState.Minimized)
+                this.ReassertTopmost();
+        });
+    }
+
     private void TryShiftPixels()
     {
         if (!Settings.Default.BurnInMitigation || DateTimeOffset.Now.Second != 0)

DesktopClock/Utilities/WindowUtil.cs

@@ -14,8 +14,11 @@ public static class WindowUtil
     private const uint SWP_NOMOVE = 0x0002;
     private const uint SWP_NOSIZE = 0x0001;
     private const uint SWP_NOZORDER = 0x0004;
+    private const uint SWP_NOACTIVATE = 0x0010;
     private const uint SWP_FRAMECHANGED = 0x0020;
 
+    private static readonly IntPtr HWND_TOPMOST = new(-1);
+
     [DllImport("user32.dll")]
     private static extern int GetWindowLong(IntPtr hwnd, int index);
 
@@ -83,6 +86,23 @@ public static void ApplyWindowVisibility(this Window window, bool showInTaskbar,
         SetWindowPos(hwnd, IntPtr.Zero, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOZORDER | SWP_FRAMECHANGED);
     }
 
+    /// <summary>
+    /// Moves the window back to the top of the topmost band so it covers the taskbar again.
+    /// </summary>
+    /// <remarks>
+    /// Topmost windows all share one band, so the shell raising itself leaves the clock buried inside it.
+    /// Assigning <see cref="Window.Topmost"/> again wouldn't help because WPF only reapplies the z-order when the value changes.
+    /// </remarks>
+    public static void ReassertTopmost(this Window window)
+    {
+        var hwnd = new WindowInteropHelper(window).Handle;
+        if (hwnd == IntPtr.Zero)
+            return;
+
+        // SWP_NOZORDER is deliberately left out because moving within the band is the whole point, and SWP_NOACTIVATE keeps focus wherever the user left it.
+        SetWindowPos(hwnd, HWND_TOPMOST, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE);
+    }
+
     /// <summary>
     /// Returns the extended style that matches the requested taskbar and Alt+Tab behavior.
     /// </summary>