Fix icon back in taskbar after Alt+Tab activation

DesktopClock.Tests/WindowUtilTests.cs

@@ -0,0 +1,47 @@
+namespace DesktopClock.Tests;
+
+public class WindowUtilTests
+{
+    private const int WsExTransparent = 0x00000020;
+    private const int WsExToolWindow = 0x00000080;
+    private const int WsExAppWindow = 0x00040000;
+
+    [Fact]
+    public void GetWindowVisibilityExtendedStyle_HideFromAltTab_SetsToolWindowAndClearsAppWindow()
+    {
+        var style = WsExTransparent | WsExAppWindow;
+
+        var updatedStyle = WindowUtil.GetWindowVisibilityExtendedStyle(
+            style,
+            showInTaskbar: true,
+            hideFromAltTab: true);
+
+        Assert.Equal(WsExTransparent | WsExToolWindow, updatedStyle);
+    }
+
+    [Fact]
+    public void GetWindowVisibilityExtendedStyle_ShowInTaskbar_SetsAppWindowAndClearsToolWindow()
+    {
+        var style = WsExTransparent | WsExToolWindow;
+
+        var updatedStyle = WindowUtil.GetWindowVisibilityExtendedStyle(
+            style,
+            showInTaskbar: true,
+            hideFromAltTab: false);
+
+        Assert.Equal(WsExTransparent | WsExAppWindow, updatedStyle);
+    }
+
+    [Fact]
+    public void GetWindowVisibilityExtendedStyle_HideTaskbarWithoutHidingFromAltTab_ClearsBothFlags()
+    {
+        var style = WsExTransparent | WsExToolWindow | WsExAppWindow;
+
+        var updatedStyle = WindowUtil.GetWindowVisibilityExtendedStyle(
+            style,
+            showInTaskbar: false,
+            hideFromAltTab: false);
+
+        Assert.Equal(WsExTransparent, updatedStyle);
+    }
+}

DesktopClock/MainWindow.xaml.cs

@@ -46,8 +46,7 @@ public MainWindow()
         _settingsPropertyChanged = (s, e) => Dispatcher.Invoke(() => Settings_PropertyChanged(s, e));
         Settings.Default.PropertyChanged += _settingsPropertyChanged;
 
-        // Not done through binding due to what's explained in the comment in WindowUtil.HideFromScreen().
-        ShowInTaskbar = Settings.Default.ShowInTaskbar;
+        ApplyWindowVisibilitySettings();
 
         // Restore the last displayed text so the window starts near its previous size.
         CurrentTimeOrCountdownString = Settings.Default.LastDisplay;
@@ -84,6 +83,7 @@ public void HideForNow()
         }
 
         this.HideFromScreen();
+        ApplyWindowVisibilitySettings();
     }
 
     /// <summary>
@@ -119,6 +119,12 @@ protected override void OnClosed(EventArgs e)
         base.OnClosed(e);
     }
 
+    protected override void OnActivated(EventArgs e)
+    {
+        base.OnActivated(e);
+        ApplyWindowVisibilitySettings();
+    }
+
     private void ConfigureTrayIcon()
     {
         if (_trayIcon == null)
@@ -155,12 +161,8 @@ private void Settings_PropertyChanged(object sender, PropertyChangedEventArgs e)
                 break;
 
             case nameof(Settings.Default.ShowInTaskbar):
-                ShowInTaskbar = Settings.Default.ShowInTaskbar;
-                this.SetHiddenFromAltTab(Settings.Default.HideFromAltTab);
-                break;
-
             case nameof(Settings.Default.HideFromAltTab):
-                this.SetHiddenFromAltTab(Settings.Default.HideFromAltTab);
+                ApplyWindowVisibilitySettings();
                 break;
 
             case nameof(Settings.Default.ClickThrough):
@@ -303,7 +305,7 @@ private void Window_SourceInitialized(object sender, EventArgs e)
 
         // Apply click-through setting.
         this.SetClickThrough(Settings.Default.ClickThrough);
-        this.SetHiddenFromAltTab(Settings.Default.HideFromAltTab);
+        ApplyWindowVisibilitySettings();
 
         UpdateTimeString();
         _systemClockTimer.Start();
@@ -315,6 +317,7 @@ private void Window_SourceInitialized(object sender, EventArgs e)
         {
             _trayIcon?.ShowNotification("Started hidden", "Use the tray icon to show it");
             this.HideFromScreen();
+            ApplyWindowVisibilitySettings();
         }
 
         // Show the window now that it's finished loading.
@@ -380,6 +383,13 @@ private void Window_StateChanged(object sender, EventArgs e)
             _systemClockTimer.Start();
             EfficiencyModeUtilities.SetEfficiencyMode(false);
         }
+
+        ApplyWindowVisibilitySettings();
+    }
+
+    private void ApplyWindowVisibilitySettings()
+    {
+        this.ApplyWindowVisibility(Settings.Default.ShowInTaskbar, Settings.Default.HideFromAltTab);
     }
 
     private void Window_KeyDown(object sender, KeyEventArgs e)

DesktopClock/Utilities/WindowUtil.cs

@@ -66,27 +66,35 @@ public static void SetClickThrough(this Window window, bool clickThrough)
     }
 
     /// <summary>
-    /// Hides or shows the window in Alt+Tab.
+    /// Applies the window's taskbar and Alt+Tab visibility.
     /// </summary>
-    public static void SetHiddenFromAltTab(this Window window, bool hideFromAltTab)
+    public static void ApplyWindowVisibility(this Window window, bool showInTaskbar, bool hideFromAltTab)
     {
+        window.ShowInTaskbar = showInTaskbar;
+
         var hwnd = new WindowInteropHelper(window).Handle;
         if (hwnd == IntPtr.Zero)
             return;
 
         var extendedStyle = GetWindowLong(hwnd, GWL_EXSTYLE);
-        if (hideFromAltTab)
-        {
-            extendedStyle |= WS_EX_TOOLWINDOW;
-            extendedStyle &= ~WS_EX_APPWINDOW;
-        }
-        else
-        {
-            extendedStyle |= WS_EX_APPWINDOW;
-            extendedStyle &= ~WS_EX_TOOLWINDOW;
-        }
+        extendedStyle = GetWindowVisibilityExtendedStyle(extendedStyle, showInTaskbar, hideFromAltTab);
 
         SetWindowLong(hwnd, GWL_EXSTYLE, extendedStyle);
         SetWindowPos(hwnd, IntPtr.Zero, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOZORDER | SWP_FRAMECHANGED);
     }
+
+    /// <summary>
+    /// Returns the extended style that matches the requested taskbar and Alt+Tab behavior.
+    /// </summary>
+    public static int GetWindowVisibilityExtendedStyle(int extendedStyle, bool showInTaskbar, bool hideFromAltTab)
+    {
+        extendedStyle &= ~(WS_EX_TOOLWINDOW | WS_EX_APPWINDOW);
+
+        if (hideFromAltTab)
+            return extendedStyle | WS_EX_TOOLWINDOW;
+
+        return showInTaskbar
+            ? extendedStyle | WS_EX_APPWINDOW
+            : extendedStyle;
+    }
 }