perf: hide main window from alt tab program switcher

Flow.Launcher/Helper/WindowsInteropHelper.cs

@@ -148,4 +148,64 @@ public static Point TransformPixelsToDIP(Visual visual, double unitX, double uni
 
         return new Point((int)(matrix.M11 * unitX), (int)(matrix.M22 * unitY));
     }
+
+    #region Alt Tab
+
+    private static int SetWindowLong(HWND hWnd, WINDOW_LONG_PTR_INDEX nIndex, int dwNewLong)
+    {
+        PInvoke.SetLastError(WIN32_ERROR.NO_ERROR); // Clear any existing error
+
+        var result = PInvoke.SetWindowLong(hWnd, nIndex, dwNewLong);
+        if (result == 0 && Marshal.GetLastPInvokeError() != 0)
+        {
+            throw new Win32Exception(Marshal.GetLastPInvokeError());
+        }
+
+        return result;
+    }
+
+    /// <summary>
+    /// Hide windows in the Alt+Tab window list
+    /// </summary>
+    /// <param name="window">To hide a window</param>
+    public static void HideFromAltTab(Window window)
+    {
+        var exStyle = GetCurrentWindowStyle(window);
+
+        // Add TOOLWINDOW style, remove APPWINDOW style
+        var newExStyle = ((uint)exStyle | (uint)WINDOW_EX_STYLE.WS_EX_TOOLWINDOW) & ~(uint)WINDOW_EX_STYLE.WS_EX_APPWINDOW;
+
+        SetWindowLong(new(new WindowInteropHelper(window).Handle), WINDOW_LONG_PTR_INDEX.GWL_EXSTYLE, (int)newExStyle);
+    }
+
+    /// <summary>
+    /// Restore window display in the Alt+Tab window list.
+    /// </summary>
+    /// <param name="window">To restore the displayed window</param>
+    public static void ShowInAltTab(Window window)
+    {
+        var exStyle = GetCurrentWindowStyle(window);
+
+        // Remove the TOOLWINDOW style and add the APPWINDOW style.
+        var newExStyle = ((uint)exStyle & ~(uint)WINDOW_EX_STYLE.WS_EX_TOOLWINDOW) | (uint)WINDOW_EX_STYLE.WS_EX_APPWINDOW;
+
+        SetWindowLong(new(new WindowInteropHelper(window).Handle), WINDOW_LONG_PTR_INDEX.GWL_EXSTYLE, (int)newExStyle);
+    }
+
+    /// <summary>
+    /// To obtain the current overridden style of a window.
+    /// </summary>
+    /// <param name="window">To obtain the style dialog window</param>
+    /// <returns>current extension style value</returns>
+    private static int GetCurrentWindowStyle(Window window)
+    {
+        var style = PInvoke.GetWindowLong(new(new WindowInteropHelper(window).Handle), WINDOW_LONG_PTR_INDEX.GWL_EXSTYLE);
+        if (style == 0 && Marshal.GetLastPInvokeError() != 0)
+        {
+            throw new Win32Exception(Marshal.GetLastPInvokeError());
+        }
+        return style;
+    }
+
+    #endregion
 }

Flow.Launcher/MainWindow.xaml

@@ -20,6 +20,7 @@
     Closing="OnClosing"
     Deactivated="OnDeactivated"
     Icon="Images/app.png"
+    SourceInitialized="OnSourceInitialized"
     Initialized="OnInitialized"
     Left="{Binding Settings.WindowLeft, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
     Loaded="OnLoaded"

Flow.Launcher/MainWindow.xaml.cs

@@ -171,6 +171,11 @@ private async void OnClosing(object sender, CancelEventArgs e)
             Environment.Exit(0);
         }
 
+        private void OnSourceInitialized(object sender, EventArgs e)
+        {
+            WindowsInteropHelper.HideFromAltTab(this);
+        }
+
         private void OnInitialized(object sender, EventArgs e)
         {
         }

Flow.Launcher/NativeMethods.txt

@@ -14,4 +14,7 @@ FindWindowEx
 WINDOW_STYLE
 
 WM_ENTERSIZEMOVE
-WM_EXITSIZEMOVE
+WM_EXITSIZEMOVE
+
+SetLastError
+WINDOW_EX_STYLE