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Article #17581: Preventing another instance of your application.

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FAQ2581C.txt   Preventing another instance of your application.
Category   :VCL
Platform    :All
Product    :C++Builder  3.x

How do I prevent another instance of my application fromj comming up 
if there is one already running?

This code will prevent a BCB application from running another
 instance.  Instead, it finds and brings to the forefront the previous
 instance.  Now it also restores the other instance even if it was
 iconic.  Put the following in WinMain() with your own Class Names,
 Application Title, and Mutex name.
     ::CreateMutex(NULL, FALSE, "YourMutexName");
     if ( GetlastError() == ERROR_ALREADY_EXISTS )
         // Found another running application with the same mutex
         // so one instance is already running.
         Application->Title="Testing";  // prohibits finding this instance
         HWND FirsthWnd, FirstChildhWnd;
         FirsthWnd = ::FindWindow("TApplication", "YourApplicationTitle"); // see Application->Title or Options|Project|Application Tab|Title
         if (::IsIconic(FirsthWnd))
             ::ShowWindow(FirsthWnd, SW_SHOWDEFAULT);
         FirstChildhWnd = ::GetLastActivePopup(FirsthWnd);
         if (FirsthWnd != FirstChildhWnd)
             ::BringWindowToTop(FirstChildhWnd); // A pop-up is active so bring it to the top too.
         Application->Title = "YourApplicationTitle";

7/2/98 10:32:32 AM

Last Modified: 01-SEP-99