create an independent hidden process

Question

I'm creating an application with its main window hidden by using the following code:

STARTUPINFO siStartupInfo;
PROCESS_INFORMATION piProcessInfo;

memset(&siStartupInfo, 0, sizeof(siStartupInfo));
memset(&piProcessInfo, 0, sizeof(piProcessInfo));

siStartupInfo.cb = sizeof(siStartupInfo);
siStartupInfo.dwFlags = STARTF_USESHOWWINDOW | STARTF_FORCEOFFFEEDBACK | STARTF_USESTDHANDLES;
siStartupInfo.wShowWindow = SW_HIDE;

if(CreateProcess(MyApplication, "", 0, 0, FALSE, 0, 0, 0, &siStartupInfo, &piProcessInfo) == FALSE)  
{
 // blah    
 return 0;
}

Everything works correctly except my main application (the one calling this code) window loses focus when I open the new program. I tried lowering the priority of the new process but the focus problem is still there.

Is there anyway to avoid this? furthermore, is there any way to create another process without using CreateProcess (or any of the API's that call CreateProcess like ShellExecute)?

My guess is that my app is losing focus because it was given to the new process, even when it's hidden.

To those of you curious out there that will certainly ask the usual "why do you want to do this", my answer is because I have a watchdog process that cannot be a service and it gets started whenever I open my main application. Satisfied?

Thanks for the help. Code will be appreciated. Jess.

Answer 1

The application you are running is taking the Window focus.

One way to work around this problem is to start your new process in a new desktop. This would prevent the application from stealing the window focus on your desktop.

The code to run a process on a new desktop should look something like this:

HDESK hOld = GetThreadDesktop( GetCurrentThreadId() );
HDESK hNew = OpenDesktop( "name", 0, FALSE, GENERIC_ALL );
SetThreadDesktop( hNew );
CreateProcess( ... );
SetThreadDesktop( hOld );
CloseDesktop( hNew );

Answer 2

Clearly the target application is not honoring the ShowWindow flags. You need to fix the launched application so that its not being greedy.