diff -r e4ee19d583bd -r c16fd81b520a GUI/ShowDesktop.cs
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/GUI/ShowDesktop.cs	Mon Sep 06 19:53:13 2010 +0000
@@ -0,0 +1,172 @@
+/*
+  
+  Version: MPL 1.1/GPL 2.0/LGPL 2.1
+
+  The contents of this file are subject to the Mozilla Public License Version
+  1.1 (the "License"); you may not use this file except in compliance with
+  the License. You may obtain a copy of the License at
+ 
+  http://www.mozilla.org/MPL/
+
+  Software distributed under the License is distributed on an "AS IS" basis,
+  WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+  for the specific language governing rights and limitations under the License.
+
+  The Original Code is the Open Hardware Monitor code.
+
+  The Initial Developer of the Original Code is 
+  Michael Möller <m.moeller@gmx.ch>.
+  Portions created by the Initial Developer are Copyright (C) 2010
+  the Initial Developer. All Rights Reserved.
+
+  Contributor(s):
+
+  Alternatively, the contents of this file may be used under the terms of
+  either the GNU General Public License Version 2 or later (the "GPL"), or
+  the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+  in which case the provisions of the GPL or the LGPL are applicable instead
+  of those above. If you wish to allow use of your version of this file only
+  under the terms of either the GPL or the LGPL, and not to allow others to
+  use your version of this file under the terms of the MPL, indicate your
+  decision by deleting the provisions above and replace them with the notice
+  and other provisions required by the GPL or the LGPL. If you do not delete
+  the provisions above, a recipient may use your version of this file under
+  the terms of any one of the MPL, the GPL or the LGPL.
+ 
+*/
+
+using System;
+using System.Runtime.InteropServices;
+using System.Windows.Forms;
+
+namespace OpenHardwareMonitor.GUI {
+  public class ShowDesktop {
+    private static ShowDesktop instance = new ShowDesktop();
+
+    public delegate void ShowDesktopChangedEventHandler(bool showDesktop);
+    
+    private event ShowDesktopChangedEventHandler ShowDesktopChangedEvent;
+
+    private System.Threading.Timer timer;
+    private bool showDesktop = false;   
+    private NativeWindow referenceWindow;
+    private string referenceWindowCaption =
+      "OpenHardwareMonitorShowDesktopReferenceWindow";
+
+    private ShowDesktop() {
+      // create a reference window to detect show desktop
+      referenceWindow = new NativeWindow();
+      CreateParams cp = new CreateParams();
+      cp.ExStyle = GadgetWindow.WS_EX_TOOLWINDOW;
+      cp.Caption = referenceWindowCaption;
+      referenceWindow.CreateHandle(cp);
+      NativeMethods.SetWindowPos(referenceWindow.Handle, 
+        GadgetWindow.HWND_BOTTOM, 0, 0, 0, 0, GadgetWindow.SWP_NOMOVE | 
+        GadgetWindow.SWP_NOSIZE | GadgetWindow.SWP_NOACTIVATE | 
+        GadgetWindow.SWP_NOSENDCHANGING);
+
+      // start a repeated timer to detect "Show Desktop" events 
+      timer = new System.Threading.Timer(OnTimer, null,
+        System.Threading.Timeout.Infinite, System.Threading.Timeout.Infinite);
+    }
+
+    private void StartTimer() {
+      timer.Change(0, 200);
+    }
+
+    private void StopTimer() {
+      timer.Change(System.Threading.Timeout.Infinite,
+        System.Threading.Timeout.Infinite);
+    }
+
+    // the desktop worker window (if available) can hide the reference window
+    private IntPtr GetDesktopWorkerWindow() {
+      IntPtr shellWindow = NativeMethods.GetShellWindow();
+      if (shellWindow == IntPtr.Zero)
+        return IntPtr.Zero;
+
+      int shellId;
+      NativeMethods.GetWindowThreadProcessId(shellWindow, out shellId);
+
+      IntPtr workerWindow = IntPtr.Zero;
+      while ((workerWindow = NativeMethods.FindWindowEx(
+          IntPtr.Zero, workerWindow, "WorkerW", null)) != IntPtr.Zero) {
+
+        int workerId;
+        NativeMethods.GetWindowThreadProcessId(workerWindow, out workerId);
+        if (workerId == shellId) {
+          IntPtr window = NativeMethods.FindWindowEx(
+            workerWindow, IntPtr.Zero, "SHELLDLL_DefView", null);
+          if (window != IntPtr.Zero) {
+            IntPtr desktopWindow = NativeMethods.FindWindowEx(
+              window, IntPtr.Zero, "SysListView32", null);
+            if (desktopWindow != IntPtr.Zero)
+              return workerWindow;
+          }
+        }
+      }
+      return IntPtr.Zero;
+    }
+
+    private void OnTimer(Object state) {
+      bool showDesktopDetected;
+
+      IntPtr workerWindow = GetDesktopWorkerWindow();
+      if (workerWindow != IntPtr.Zero) {
+        // search if the reference window is behind the worker window
+        IntPtr reference = NativeMethods.FindWindowEx(
+          IntPtr.Zero, workerWindow, null, referenceWindowCaption);
+        showDesktopDetected = reference == referenceWindow.Handle;
+      } else {
+        // if there is no worker window, then nothing can hide the reference
+        showDesktopDetected = false;
+      }
+
+      if (showDesktop != showDesktopDetected) {
+        showDesktop = showDesktopDetected;
+        if (ShowDesktopChangedEvent != null) {
+          ShowDesktopChangedEvent(showDesktop);
+        }
+      }
+    }
+
+    public static ShowDesktop Instance {
+      get { return instance; }
+    }
+
+    // notify when the "show desktop" mode is changed
+    public event ShowDesktopChangedEventHandler ShowDesktopChanged {
+      add {
+        // start the monitor timer when someone is listening
+        if (ShowDesktopChangedEvent == null)           
+          StartTimer();
+        ShowDesktopChangedEvent += value;
+      }
+      remove {
+        ShowDesktopChangedEvent -= value;
+        // stop the monitor timer if nobody is interested
+        if (ShowDesktopChangedEvent == null)
+          StopTimer();
+      }
+    }
+
+    private static class NativeMethods {
+      private const string USER = "user32.dll";
+
+      [DllImport(USER, CallingConvention = CallingConvention.Winapi)]
+      public static extern bool SetWindowPos(IntPtr hWnd,
+        IntPtr hWndInsertAfter, int X, int Y, int cx, int cy, uint uFlags);
+
+      [DllImport(USER, CallingConvention = CallingConvention.Winapi)]
+      public static extern IntPtr FindWindowEx(IntPtr hwndParent,
+        IntPtr hwndChildAfter, string lpszClass, string lpszWindow);
+
+      [DllImport(USER, CallingConvention = CallingConvention.Winapi)]
+      public static extern IntPtr GetShellWindow();
+
+      [DllImport(USER, CallingConvention = CallingConvention.Winapi)]
+      public static extern int GetWindowThreadProcessId(IntPtr hWnd,
+        out int processId);
+    }  
+  }
+}