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Posted 20 Jan 2008
Licenced CPOL

Window Tabifier

, 29 Mar 2008
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A simple application for hosting several Windows in one parent window
Sample Image



This program allows to host several open Windows in one parent window so that you can easily access and navigate between them, as well as clean up space in the taskbar. The idea of creating this program came to me when I was reading an article by Jay Nelson: Hosting EXE Applications in a WinForm project. Instead of hosting just a single executable inside a WinForm project, I decided to have a tabcontrol and host different Windows on different tabs. This will allow to group similar Windows together, easily navigate between them and clean up space in the taskbar. Interested? In that case, let's start exploring the application.


All the functionality of this application is achieved using Windows API functions, so you should be familiar with basic winapi programming. Consequently you should know what P/Invoke is and how it works. If you are familiar with the article: Window Tray Minimizer, then it will help you a lot.

How the Program Works

When you run the application, it hides the main form and an icon is shown in the system tray. If you right-click the icon, a context menu will be shown which has two main buttons: 'Tab Windows' and 'Tab all Windows'. When you click 'Tab Windows', a new window will pop up with a list of open Windows. The list can be filtered by the title of the Windows. When you select the Windows you wish to tabify and click 'OK', a new window will be created and all the checked Windows will be hosted in a tabcontrol. There will be one more tabpage called Menu which has two buttons: one for adding open Windows to the tabcontrol and another for choosing files that will be automatically opened in new tabs. You can also drag & drop files or folders from Windows Explorer on this tabpage for having them opened in new tabs automatically. You can navigate between tabs by clicking Ctrl+1, Ctrl+2 and so on or you can just simply hover mouse over the tab and it will be selected automatically. When selected tab changes, icon of the host window is changed either with the icon of the executable file that created current window or with the icon of the window itself. Minimizing the host window minimizes it to tray, but if it is not what you want, you can turn off the feature from the options dialog.

Code Behind the Application

Before we begin exploring the application itself, I'd like to introduce a class for storing simple properties of a window and methods for manipulation on it. The main properties are: Handle, Location, Parent, Size and Title. The main methods include closing the window, getting the path of the executable file that created the window, moving it, setting/restoring parent and setting style. There is also one static method that enumerates all open Windows. The class has one constructor that takes the window's handle as a parameter and sets its simple properties. Here is a class diagram:


Enumerating Windows and Filtering Them

When you click the 'Tab Windows' button, a window is shown which lists all open Windows. In order to enumerate all Windows, you should call the winapi function called EnumWindows. The function takes two parameters. The first one is a pointer to a callback function. The code snippet below shows how this function works:

public static List<window> GetOpenWindows()
openwnd = new List<window>();

winapi.EnumWindowsProc callback = new winapi.EnumWindowsProc(EnumWindows);
winapi.EnumWindows(callback, 0);

List<window> result = new List<window>(openwnd);

result.RemoveAt(result.Count - 1);

return result;

private static bool EnumWindows(IntPtr hWnd, int lParam)
if (!winapi.IsWindowVisible(hWnd) || hWnd == winapi.statusbar)

return true;

openwnd.Add(new window(hWnd));

return true;

After this, we need to filter this list. Firstly, we need to get rid of the Windows that were opened by our application so that we don't get host Windows hosting other host Windows. This can be done for each returned window by finding the path of the executable that created the window and comparing it to our application's location. Secondly, if the user has selected to ignore Windows without a title, we have to remove them.

Finding Windows Executable

These are the steps required to find the path of the executable that created a given window:

  1. Get the process id that created the specified window using the GetWindowThreadProcessId() function
  2. Get a handle of the process by OpenProcess() function
  3. Get the executable path by calling GetModuleFileNameEx() function

All these functions are winapi functions imported by dllimport attribute. Here is the actual implementation ported to C#:

public string GetExecutablePath()

uint dwProcessId;

//Get the process id
winapi.GetWindowThreadProcessId(handle, out dwProcessId);

//Get the handle of the process
IntPtr hProcess = winapi.OpenProcess(winapi.ProcessAccessFlags.VMRead |
 winapi.ProcessAccessFlags.QueryInformation, false, dwProcessId);

//Get the executable path
StringBuilder path = new StringBuilder(1024);
winapi.GetModuleFileNameEx(hProcess, IntPtr.Zero, path, 1024);


return path.ToString();

Filtering Windows

At this point we have a variable of List<window> class. In C# 2.0, we can use FindAll method of List<T> class to filter it.

private void GetWindows()
 if (Properties.Settings.Default.Ignore)
 windows = window.GetOpenWindows().FindAll(delegate(window wnd) {

return wnd.Title.Length > 0 && wnd.GetExecutablePath() != Application.ExecutablePath; });
windows = window.GetOpenWindows().FindAll(delegate(window wnd) {
 return wnd.GetExecutablePath() != Application.ExecutablePath; });

In C# 3.0, you can make use of a new feature called Lambda expressions and rewrite it like this:

private void GetWindows()
 if (Properties.Settings.Default.Ignore)
 windows = window.GetOpenWindows().FindAll((window wnd)=>wnd.Title.Length>0 &&
windows = window.GetOpenWindows().FindAll((window wnd) => wnd.GetExecutablePath()
!= Application.ExecutablePath);

Hosting Windows

When a user selects those Windows that are to be tabbed and clicks OK, a new 'host' window is created and selected Windows are passed to it. When the host is displayed, it adds a new tabpage for each window and displays the window.

private void ProcessWindows(List<window> windows)
lock (tabs)
 int startindex = tabs.Items.Count - 1;
 for (int i = startindex; i < windows.Count; i++)
 int count = tabs.Items.Add(new FATabStripItem(windows[i].Title, null));

 windows[i].SetStyle(winapi.GWL_STYLE, (IntPtr)winapi.WS_VISIBLE);
 windows[i].Move(tabs.Location, tabs.Size, true);

Whenever a tabpage is closed, the window that was displayed on it is released.

private void Release(window wnd)
wnd.SetStyle(winapi.GWL_STYLE, (IntPtr)wnd.PreviousStyle);
wnd.Move(wnd.Location, wnd.Size, true);

Managing Drag & Drop

Detecting drag 'n' drop of files from Windows Explorer on the menu tab is detected by the component that comes with the source code of this book: Windows Forms 2.0 Programming. When files or folders are dropped on the form or user selects them by clicking 'Open files in new tab', they are filtered and a new process is started using the filename.

private void ProcessFiles(string[] files)
 foreach (string filename in files)
 //If it isn't a shortcut then process it.
 if (!filename.EndsWith(".lnk"))
    ParameterizedThreadStart thrparam = new ParameterizedThreadStart(ProcessFile);
    Thread thr = new Thread(thrparam);

The ProcessFile method starts a new process based on a parameter, waits 5 seconds for an application to become idle and then checks its MainWindowHandle property. If a folder was dropped, then it tries to get the handle to the window which was created by using winapi FindWindow function.

private void ProcessFile(object filename)
 string path = filename as string;
 if (File.Exists(path))
 Process proc = Process.Start(path);

 if (proc != null)
    if (proc.MainWindowHandle != IntPtr.Zero)
    lock (hostedwindows)
    hostedwindows.Add(new window(proc.MainWindowHandle));
 if (Directory.Exists(path))
    int i = 0;

    //Tries five times to find new window
    IntPtr handle = IntPtr.Zero;
    while (handle==IntPtr.Zero && i<5)
    // 'CabinetWClass' is the class name of explorer windows.
    handle = window.FindWindow("CabinetWClass", Path.GetFileName(path));

    if (handle != IntPtr.Zero)
    lock (hostedwindows)
    hostedwindows.Add(new window(handle));

Navigation Between Tabs

Except just clicking the tab with mouse which you wish to select there are two ways to navigate between them: You can either click Ctrl+1, Ctrl+2, etc. at the same time to switch to the corresponding tab or you can simply hover mouse over the tab and it will be selected automatically. The code snippets below show how these are accomplished.

Code Snippet for Ctrl+1, Ctrl+2, etc.

private void tabs_KeyDown(object sender, KeyEventArgs e)
 //Check if Ctrl key is pressed and that there is
 //corresponding tab item to the number which was pressed.
 if (e.Control && e.KeyValue>48 && e.KeyValue<58 && tabs.Items.Count>=(e.KeyValue-48))
 tabs.SelectedItem = tabs.Items[e.KeyValue - 49];

Code Snippet for Automatically Selecting Tab when Mouse is Moved Over It

private void tabs_MouseMove(object sender, MouseEventArgs e)
 //Make sure that there is tab under mouse and that automatic selection is enabled.
 FATabStripItem c = tabs.GetTabItemByPoint(e.Location);
 if (c != null && Properties.Settings.Default.SelectonHover)
 tabs.SelectedItem = tabs.Items[tabs.Items.IndexOf(c)];

Host Window Icon

When you change active tab in host window, the host window icon changes either with the icon of the executable file that created the currently displayed window or with the icon of the window itself that is displayed. So we need to retrieve either the executable icon or the window's icon.

Retrieving Executable Icon

In order to retrieve the executable icon we need to call SHGetFileInfo() and pass the path of the executable file and an instance of SHFILEINFO structure. After you have retrieved a handle to the icon, you must call DestoyIcon() API to prevent a memory leak.

private Icon GetIcon()
 System.Drawing.Icon icon = null;
 string path = GetExecutablePath();

 if (System.IO.File.Exists(path))
    //Retrieve SHFILEINFO type variable
    winapi.SHFILEINFO info = new winapi.SHFILEINFO();
    winapi.SHGetFileInfo(path, 0, ref info, (uint)Marshal.SizeOf(info),
            winapi.SHGFI_ICON | winapi.SHGFI_SMALLICON);

    //Create icon and destroy the handle
    System.Drawing.Icon temp = System.Drawing.Icon.FromHandle(info.hIcon);
    icon = (System.Drawing.Icon)temp.Clone();

 return icon;

Retrieving Window Icon

In order to retrieve window icon, I used the code snippet from this article: Screen Captures, Window Captures and Window Icon Captures with Spy++ Style Window Finder! with small modifications. Here it is:

private Icon GetWindowIcon()
 int result;

 winapi.SendMessageTimeout(handle, winapi.WM_GETICON, winapi.ICON_SMALL, 0,
 winapi.SMTO_ABORTIFHUNG, 1000, out result);

 IntPtr IconHandle = new IntPtr(result);

 if (IconHandle == IntPtr.Zero)
 result = winapi.GetClassLong(handle, winapi.GCL_HICONSM);
 IconHandle = new IntPtr(result);

 if (IconHandle == IntPtr.Zero)
 winapi.SendMessageTimeout(handle, winapi.WM_QUERYDRAGICON, 0, 0,
 winapi.SMTO_ABORTIFHUNG, 1000, out result);
 IconHandle = new IntPtr(result);

 if (IconHandle == IntPtr.Zero)
 return null;

 System.Drawing.Icon temp = System.Drawing.Icon.FromHandle(IconHandle);
 System.Drawing.Icon icon = (System.Drawing.Icon)temp.Clone();


 return icon;

Managing Start-up

You can add the program to start-up from the options Window. To add program to start-up, you need to navigate to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run key, create a new string and set its value equal to the application's path. Removing the program from start-up is easier: you just remove the value. The code snippet below shows how to do it:

 Write = @"HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run")]
private void startup(bool add)
RegistryKey key = Registry.CurrentUser.OpenSubKey(@"Software\Microsoft\Windows\
 CurrentVersion\Run", true);

if (add)
key.SetValue("Window Tabifier", "\"" + Application.ExecutablePath + "\"");
key.DeleteValue("Window Tabifier");


Making the Application Single-instance

If you try to launch the second instance of the application, you will get a message box saying that it is already running. This is achieved using the mutex class. Mutex allows to share resources between threads. When the first instance of the program is launched, it creates a new mutex. When a second instance is launched, it checks the existence of the mutex. If it exists, then it exits. When the first instance quits, it releases the existing mutex.

static void Main()
Mutex mt = null;

//Try to open existing mutex
mt = Mutex.OpenExisting("Window Tabifier");
 catch (WaitHandleCannotBeOpenedException)


 if (mt == null)
 //If the mutex doesn't exist create it and launch the application.
mt = new Mutex(true, "Window Tabifier");
 Application.Run(new Main());

 //Tell GC not to destroy mutex until the application is running and
//release the mutex when application exits.
//The mutex exists so exit
MessageBox.Show("Application already running");

Possible Enhancements

These are possible features that would make the application more useful:

  • Detecting window opening automatically and adding it to the host window
  • Detecting WM_SETTEXT message for tabbed Windows in order to update tab title.

Both features require setting Windows hooks.

Points of Interest

While experimenting with this application, I found that if you start a new process through file shortcut, then the return value is always null.


I would like to thank Giorgi Moniava for the advice he gave me.


  • 20th January, 2008 - Initial release

  • 11th February, 2008 - version 1.5

    Bugs Fixed

    • Bug #1: When a tabbed window is released, it has the same state as before it was tabbed. (If the window was maximized before tabbing, it will be maximized after it is released.)
    • Bug #2: When a minimized window is released, you no more need to right-click it with the mouse and click restore in order to open it, you can just click it with the mouse as you usually would.

    Features Added

    • Feature #1: You can now drag and drop a folder on the host window and it will be automatically opened in a new tab.
  • 6th March, 2008 - version 1.6

    Features Added

    • Feature #1: A tab is selected automatically when the mouse is moved over it.
  • 20th March, 2008 - version 1.8

    Features Added

    • Feature #1: When you change the active tab in the host window, the host window icon is set to the icon of the executable file that created the currently displayed window.
    • Feature #2: Host window minimizes to system tray. This feature can be turned off from the options dialog.
  • 29th March, 2008 - version 1.9

    Features Added

    • Feature #1: When you change the active tab in the host window, the host window icon changes either with the icon of the executable file that created the currently displayed window or with the icon of the window itself. This behaviour can be configured from the options dialog.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Giorgi Dalakishvili
Software Developer
Georgia Georgia
No Biography provided

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Comments and Discussions

Questiondoes not work for every program Pin
Member 129822817-Feb-17 6:12
memberMember 129822817-Feb-17 6:12 
QuestionGreat application! Pin
Jack Liu Angel12-Dec-14 17:09
memberJack Liu Angel12-Dec-14 17:09 
Questionmy votes Pin
khoirom14-Aug-14 17:40
memberkhoirom14-Aug-14 17:40 
QuestionFocus problem Pin
khoirom14-Aug-14 17:39
memberkhoirom14-Aug-14 17:39 
QuestionDrag and Drop not working properly Pin
timir1231-Jan-14 4:10
membertimir1231-Jan-14 4:10 
QuestionProblem in using this code. Pin
Mahesh Murty13-Oct-12 0:51
memberMahesh Murty13-Oct-12 0:51 
QuestionNice work Pin
ghvnd10-Sep-12 1:17
memberghvnd10-Sep-12 1:17 
GeneralMy vote of 5 Pin
ghvnd10-Sep-12 1:13
memberghvnd10-Sep-12 1:13 
totally awesome!!!
Very good work Smile | :)
Questionhow to embedd the popps also in the window Pin
deveoper1234521-Oct-11 2:52
memberdeveoper1234521-Oct-11 2:52 
GeneralMy vote of 5 Pin
Indivara25-Nov-10 16:25
professionalIndivara25-Nov-10 16:25 
Generalcool Pin
Member 30146966-Sep-10 21:58
memberMember 30146966-Sep-10 21:58 
QuestionSingle process can hang all other processes Pin
blahblah996-Aug-10 6:43
memberblahblah996-Aug-10 6:43 
GeneralNice application! Congratulations Pin
Wojciech28-Apr-09 8:32
memberWojciech28-Apr-09 8:32 
GeneralRe: Nice application! Congratulations Pin
Giorgi Dalakishvili28-Apr-09 8:35
mentorGiorgi Dalakishvili28-Apr-09 8:35 
GeneralRe: Nice application! Congratulations Pin
Wojciech28-Apr-09 8:52
memberWojciech28-Apr-09 8:52 
QuestionPls help for FarsiLibrary Pin
mightygirls16-Apr-09 23:06
membermightygirls16-Apr-09 23:06 
AnswerRe: Pls help for FarsiLibrary Pin
Giorgi Dalakishvili18-Apr-09 5:28
mentorGiorgi Dalakishvili18-Apr-09 5:28 
Generaldamn awesome Pin
Xmen Real 20-Mar-09 4:20
professional Xmen Real 20-Mar-09 4:20 
GeneralRe: damn awesome Pin
Giorgi Dalakishvili20-Mar-09 6:25
mentorGiorgi Dalakishvili20-Mar-09 6:25 
GeneralRe: damn awesome Pin
Xmen Real 20-Mar-09 6:28
professional Xmen Real 20-Mar-09 6:28 
GeneralThis app rules Pin
Vodstok24-Dec-08 4:24
memberVodstok24-Dec-08 4:24 
GeneralRe: This app rules Pin
Giorgi Dalakishvili24-Dec-08 7:44
mentorGiorgi Dalakishvili24-Dec-08 7:44 
GeneralRe: This app rules Pin
Vodstok24-Dec-08 8:58
memberVodstok24-Dec-08 8:58 
GeneralRe: This app rules Pin
Giorgi Dalakishvili23-Nov-09 1:57
mentorGiorgi Dalakishvili23-Nov-09 1:57 
GeneralMy vote of 1 Pin
ProJester12-Dec-08 10:43
memberProJester12-Dec-08 10:43 

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