Virtual Desktop: A Simple Desktop Management Tool

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Introduction

A few months ago, one of my colleagues was using a tool that was managing multiple desktops. I was wondering how the tool could manage multiple desktops. I thought it would be just hiding-and-displaying the application windows for different desktops when a user switches between them. As a matter of curiosity, I started studying multiple desktops and ended up with this article.

As I went through the details, I found that I was wrong in thinking that the tool was just hiding-and-displaying the application windows for different desktops. Even the thought that the "Desktop" we see is just a directory was wrong. Let's see how it works.

Window Station and Window Desktop

Actually Windows uses Window Station and Desktop architecture to provide additional security. For the time being, we can refer to "Desktop" as a logical display surface, which contains User Interface Objects (GDI objects) and User Objects. A Window Station is a secure kernel object which contains a clipboard, an atom table, and one or more desktop objects. There exists a default window station "WinSta0", an interactive window station. "WinSta0" is the only interactive window station that can display a user interface or receive user input. All other window stations are non-interactive. By default, there exist three Desktops in an interactive window station : Default, WinLogon and ScreenSaver.

A Desktop is also a secure kernel object. When a new desktop is created, it is associated with the current window station of the calling process. There will always be only one desktop visible (Active) and ready to receive user inputs, provided the desktop is associated with an interactive window station i.e. WinSta0. This active desktop is called the Input Desktop.

As I specified, there exist three desktops in an interactive window station: Default, WinLogon and ScreenSaver. The screen prompting to press ALT + CTL + DEL to login is the WinLogon desktop. Whenever the user logs in, the Default desktop is created and made visible. This "Default" is the default active desktop for any logged in user. When you press ALT + CTL + DEL, you'll be switched back again to the WinLogon desktop. The ScreenSaver desktop will be made visible whenever the screen saver gets activated. As these desktop names are case-insensitive, there could be only one desktop of a specific name in a window station. But a desktop name can be repeated in different window stations. The purpose behind Window Station and Desktop objects is to provide top level isolation between processes.

About the Virtual Desktop (A Sample Application)

The Virtual Desktop Tool helps you to create and switch between different desktops. It even gives you an illusion of switching the application from one desktop to another. But this isn't true as any running application cannot be moved from one desktop to other. As I said, it's just an illusion. The application will be closed in the current desktop and will be launched on the specified desktop. This may cause loss of any unsaved data of the application and may not persist the state as it will be restarted.

The application is using hooks to display "Move To" menu options in the applications Control Panel (System Menu). For more details about the hooks, I would refer this article. I will give you an overview of different APIs used and classes built in the application. Rest of the code in the application is self explanatory and (what I think is) well documented.

Different APIs Used and Classes Built

GetProcessWindowStation

It retrieves the handle to the current Window Station of the calling process. The retrieved handle is used to enumerate all the desktops of the window station.

CreateDesktop

It creates a new Desktop with the specified name. This newly created desktop will be associated with the Window Station of the calling process and will be assigned to the calling thread.

OpenDesktop

It opens the specified Desktop. The handle returned by this function is used to switch between desktops.

CloseDesktop

It closes an open handle to Desktop.

SwitchDesktop

This makes the specified Desktop visible and ready to receive user inputs (i.e. makes it Active).

GetThreadDesktop

It retrieves the handle to the Desktop associated with the specified thread.

GetUserObjectInformation

It gives information about the Window Station and Desktop Objects.

The application has a class called CDesktopManager, in which all the desktop related activities are wrapped up. The application solution has a DLL Project, in which all the windows hook functionalities are wrapped up. This Event Hooker DLL is responsible for inserting menu options into the System Menu of the other applications.

Points of Interest

When we create a new desktop and switch to it, it shows nothing. The desktop will be blank(with just a wallpaper visible) -- that's because no process is running on that desktop. So, to avoid that, I launch an Explorer shell whenever I create a new desktop. I think I could add a feature to launch a new process/application on a specified desktop. And so I did in the current update. I have a few more features in mind. I'll keep updating whenever I complete them.

Revision History

• 17 Nov 2007 : Initial release
• 27 Dec 2007 : The application was exiting once it switches the desktop. It wasn't programmed to stay in memory any longer after desktop switch. But in this release the application launches a new instance of its own after desktop switch and then exits. This makes users feel that the application is always there for them in all desktops. This change has been made after reading one of the comments posted by a reader.
• 1 Jun 2008 : The feature of launching application is been incorporated. Also few bugs I found have been fixed.
• 25 July 2008 : Modified the code to encorporate following features:
  • Removed the bug of hooking my own application. :D
  • Added featue of shortcut-keys to easily navigate between the desktops.
  • Displaying the current desktop name in the application icon tooltip [so you don't get confused on which desktop you are !].
  • Tested on Vista also.

If you find a bug in the application or any feature to be embeded, please let me know, so that I can work on it.

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cool, vb.net version? rio_p 8:44 3 May '09   can you give me some example application like this using vb.net? Sign In·View Thread·PermaLink Global shortcuts do not work... Vincent Marie 7:58 28 Apr '09   Very good program !!! however, global shortcuts like + E (to open an explorer window) are still redirected to the default desktop. Sign In·View Thread·PermaLink Re: Global shortcuts do not work... Malli_S 3:58 7 May '09   Thanks Vincent, I'll look into the issue and will fix in the next update. With Regards, Mallinathk. [Delegates]      [Virtual Desktop]      [Tray Me !] -Malli...! Sign In·View Thread·PermaLink Lauching an application in desktop created in other machine TVRD 23:25 13 Apr '09   Hi, I wanted to create a process and show it in the desktop which is present in other machine. Is this possible? Thanks, Ramadevi. Sign In·View Thread·PermaLink Re: Lauching an application in desktop created in other machine Malli_S 4:02 7 May '09   As per my knowledge, you can't move the process across the desktops. The process' desktop is assigned at the time of/before launching it. The only way I found to move the process across the desktop (which is actually not the movement of process) is kill the process from the current desktop and relaunch it in the another desktop. [Delegates]      [Virtual Desktop]      [Tray Me !] -Malli...! Sign In·View Thread·PermaLink Moving a Process Sachin_Developer 7:22 6 Feb '09   Is there any way to move a window or process from one desktop to another without killing/closing that process? I tried SetThreadDesktop function it seems that its not working because after applying this function my application remains on the same Desktop?? Sky is the limit... Sign In·View Thread·PermaLink Re: Moving a Process Malli_S 4:06 7 May '09   Hi Sachin, There's no way out to move the process' across the desktops. MSDN says "The SetThreadDesktop function will fail if the calling thread has any windows or hooks on its current desktop (unless the hDesktop parameter is a handle to the current desktop)." What you're trying to do will work fine with the Windows Services. With Regards, Mallinathk. [Delegates]      [Virtual Desktop]      [Tray Me !] -Malli...! Sign In·View Thread·PermaLink Any way to close the desktop? sujianloma 23:55 17 Dec '08   I can not find a proper function to close a desktop after it is created.I just find a tricky way to do this ( from another guy's article ) :kill all processes belong to a special desktop. But the problem is how to enum all processed belonged to a special desktop?Could anybody figure out a solution? Thanks Sign In·View Thread·PermaLink Very optimistic raghugada 20:06 5 Aug '08   Its excellent to switch between desktops and it works fine without any errors. So now we can have more than one desktop running on the same machine as its in linux. Sign In·View Thread·PermaLink Here're already exists solutions Cuchuk Sergey 21:11 28 Jul '08   Here're already exists solutions such as http://virtuawin.sourceforge.net/[^] that has a lot of plugins with it and works well with many extraordinary situations and some others So what the new your project brings? Sign In·View Thread·PermaLink Re: Here're already exists solutions Malli_S 20:23 29 Jul '08   What I could see after having a look at the application is that the application is not creating any new desktop (may be i misunderstood or VirtuaWin is managing the feature with some other logic ). The application may be managing the "virtual desktops" on the existing desktop only. Here I'm not marketing out my product , but I'd like to specify that I'm dealing with the "Windows Desktop Object" (No comments about VirtuaWin product regarding this ! ). I'd be glad if you could suggest any enhancements ! -Malli...! Sign In·View Thread·PermaLink Excellent, it works fine! Tage Lejon 23:50 27 Jul '08   and looking forward to the new features you will add in to this powerful and useful code/application. Sign In·View Thread·PermaLink Very interesting Paul Conrad 17:35 26 Jul '08   Interesting article. Bookmarking it "The clue train passed his station without stopping." - John Simmons / outlaw programmer "Real programmers just throw a bunch of 1s and 0s at the computer to see what sticks" - Pete O'Hanlon Sign In·View Thread·PermaLink Using CloseDesktop TyrionTheImp 3:18 26 Jun '08   Hi Malli, Thanks for writing a super app like this ! i was going thru ur source code and saw that ur calling CloseDesktop() soon after calling OpenDesktop and SwitchDesktop.Can you please tell why this is done ? Thanks Sign In·View Thread·PermaLink Re: Using CloseDesktop Malli_S 21:32 13 Jul '08   Hi TyrionTheImp, I apologize for my late reply, as because I couldn't get time to login into the codeproject. Anyway, the CloseDesktop() function just closes the handle to the desktop object that was obtained by CreateDestop(), OpenDesktop or OpenInputDesktop() function. And since the work is done with the handle, and is no more needed, I'm closing that desktop handle soon after calling OpenDesktop() and SwitchDesktop(). -Malli...! Sign In·View Thread·PermaLink one prob in my system P s G 22:25 4 Jun '08   hi..i like ur app... but in my PC after i switch to a desktop, tht desktop stays for a few seconds only and then it switches back to the default desktop ....wt cud b the reason ? Sign In·View Thread·PermaLink Re: one prob in my system Malli_S 2:27 5 Jun '08   Hey thanks for the reporting the bug. But I wonder about the error. Are you sure that it switches back to default desktop ? How did you confirm that it switches back to default desktop ? Detailed information will help me to rectify the bug. -Malli...! Sign In·View Thread·PermaLink Excellent App (Shortcut-keys?) David B. Taylor 3:46 2 Jun '08   Really excellent stuff. What about some shortcut-keys to easily flip between your desktops? I'm thinking Ctrl+1, Ctrl+2 etc... Gineer Sign In·View Thread·PermaLink 1.00/5 (1 vote) Re: Excellent App (Shortcut-keys?) Malli_S 2:28 5 Jun '08   Yup ! That's a nice suggestion friend. surely I'll consider it for next update. -Malli...! Sign In·View Thread·PermaLink To create interactive window station under other than system account... masaniparesh 4:02 29 Nov '07   Hi, Could you please tell me if it is possible to create interactive window station under other than system account? My problem is i am creating interactive process from windows service which is running under domain account. So if i could create interactive window then only interactive process will get created. Let me tell you something more that microsoft providing interactive service only under system account. So if you know is there any way to create interactive service under other than system account then it will really a helpful to me. Thanks in advance, Paresh Sign In·View Thread·PermaLink Re: To create interactive window station under other than system account... Malli_S 4:24 30 Nov '07   I think a given login session can have only one Interactive Window Station. The standard versions of windows have only one Interactive Window Station. But Server versions can have more than one Interactive Window Station. I need to see details about interactive window station creation. If I get anything, I'll let u know. And do add to my knowledge, if you get it. -Malli...! Sign In·View Thread·PermaLink Re: To create interactive window station under other than system account... masaniparesh 21:30 30 Nov '07   Thanks, One more thing if you know, How to create process as another user from application which is running under system account. I wrote following code to achieve this but still it is creating new process as system only: IntPtr userToken = IntPtr.Zero; uint sessionId = WTSGetActiveConsoleSessionId(); WTSQueryUserToken(sessionId, ref userToken); // set startup parameters. STARTUPINFO si = new STARTUPINFO(); si.cb = Marshal.SizeOf(si); si.lpDesktop = @"Winsta0\default"; si.dwFlags = STARTF_USESTDHANDLES; si.hStdOutput = (IntPtr)hStdOutput; si.hStdError = (IntPtr)hStdError; si.wShowWindow = STARTF_USESHOWWINDOW; // needed to create a new process SecurityAttributes sa = new SecurityAttributes(); sa.InheritHandle = false; sa.SecurityDescriptor = IntPtr.Zero; sa.Length = Marshal.SizeOf(sa); PROCESS_INFORMATION pi = new PROCESS_INFORMATION(); bool newProcessCreated = CreateProcessAsUser( userToken, null, commandPath, ref sa, ref sa, false, (int)ProcessPriorityTypes.Normal, IntPtr.Zero, null, ref si, out pi); Thanks, Paresh Sign In·View Thread·PermaLink Re: To create interactive window station under other than system account... SNI 0:16 31 Oct '08   Paresh, you must be thinking how I am asking this question to you. I am compiling some code with following functions WTSGetActiveConsoleSessionId WTSQueryUserToken CreateEnvironmentBlock .But for all above functions it giving me "error C2065: 'WTSGetActiveConsoleSessionId' : undeclared identifier". For WTSGetActiveConsoleSessionId i have added "WtsApi32.lib" and #define _WIN32_WINNT 0x0501 in my stdAfx.h. Please let me know how to resolve other compile errors for WTSQueryUserToken & CreateEnvironmentBlock. Thanks SNI jhghjghj Sign In·View Thread·PermaLink Re: To create interactive window station under other than system account... masaniparesh 1:54 31 Oct '08   Please look below articles: http://www.eggheadcafe.com/tutorials/aspnet/2132f6ee-47db-4e6a-b446-4800e91ee809/get-the-windows-terminal.aspx http://www.eggheadcafe.com/tutorials/aspnet/08772e71-a1fd-4ba1-8135-ae053e28433a/generate-user-token-which.aspx Regards, Paresh Sign In·View Thread·PermaLink Re: To create interactive window station under other than system account... masaniparesh 1:44 31 Oct '08   Malli, I came out with the solution long back but now I am replying. It is not possible to create interactive window station other than System account running context. I have used psexec.exe utility to create the process under system account and kept windows service is under domain account. Thanks, Paresh Sign In·View Thread·PermaLink

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