Using ShellExecute or CreateProcess caller lose its focus

[sdancer75]

I want to call an external application (created by me) using ShellExecute or CreateProcess. It is just an update application for the main app. The problem is, what ever I tried I failed to get window focus back to my main app when the process (update app) is terminated. I created a simple MFC/SDI app that calls window's notepad under "C:\windows\notepad.exe" which suffers from the same problem, just to show you what I mean. I need the parent window -which is the main app- to be disabled (like a modal dialog box behaviour) until the new app -update application- will finish its job. PS:If I do not disable the main window with EnableWindow(FALSE) I have paint corruption with windows XP and back when I move the update application. Here an example: http://www.filedropper.com/shellexecutecreateprocesstestapp[^]

sdancer75

[Richard Andrew x64]

You could wait on the process handle returned by ShellExecute or CreateProcess, this will let you know when the child process has exited. Then you could use BringWindowToTop to bring your main application window to the foreground.

The difficult we do right away... ...the impossible takes slightly longer.

[sdancer75]

Thank you for your answer. As you can see in the code I am using WaitForSingleObject. I tried to use also the BringWindowToTop with no luck. What ever I tried I had no success.

sdancer75

[Lost User]

sdancer75 wrote:

As you can see ... What ever I tried I had no success.

We cannot see anything, you need to show your code and explain where it goes wrong.

[Jochen Arndt]

When the external update process should also update the executable of your main application, that must be terminated before the new exe file can be copyied. So there is no need to get the focus back. A typical sequence for such a process:

• Ask the user if the update should be installed
• Perform closing tasks that are time consuming or require user interaction like closing open documents
• Start the update process
• Terminate your application
• The update process should check if there is a running instance of your application (after a short wait time) and terminate with an error if so
• The update process might restart your application

In another post you mentioned that you are using WaitForSingleObject to wait for the update process to be terminated. If you call that from within your main thread, your application's message loop is blocked so that paint events are not processed. If you don't want to update the executable itself and must wait for the external process to be finished start the process from within a worker thread where you can call WaitForSingleObject without blocking the message loop. Use a global state variable indicating that the update is executing to disallow specific tasks of your application or just show a modal dialog that is closed automatically when the update has finished.

[Victor Nijegorodov]

> I need the parent window -which is the main app- to be disabled (like a modal dialog box behaviour) until the new app -update application- will finish its job. Did you try to hide or minimize the "parent window" instead?

[sdancer75]

Yes this way it works but I dont want to minimize the parent window. I need a modal like behaviour.

sdancer75

[sdancer75]

Quote:

When the external update process should also update the executable of your main application, that must be terminated before the new exe file can be copyied. So there is no need to get the focus back.

I have managed this kind of problems with success so, dont bother with that.

Quote:

In another post you mentioned that you are using WaitForSingleObject to wait for the update process to be terminated. If you call that from within your main thread, your application's message loop is blocked so that paint events are not processed.

Thats correct. Windows Vista/Win7/Win8 does not have problems with paint events but XP they have. For that reason I want to disable the parent to avoid such kind of problems.

Quote:

If you don't want to update the executable itself and must wait for the external process to be finished start the process from within a worker thread where you can call WaitForSingleObject without blocking the message loop. Use a global state variable indicating that the update is executing to disallow specific tasks of your application or just show a modal dialog that is closed automatically when the update has finished.

I update the executables too, but I dont have problems with that. If you download the sample code, you will understand the focus problem i currently have.

sdancer75

[sdancer75]

I posted a link in my 1st post with a sample MFC/SDI application that have all the code you need. http://www.filedropper.com/shellexecutecreateprocesstestapp[^]

sdancer75

[Victor Nijegorodov]

But what is a problem for you to attach a piece of code to your post?

[sdancer75]

Hi, No problem at all, I just gave all the code in the link. Anyway, I attach you the most important code from the sample app.

void CMainFrame::OnRunExternalApp() {

SHELLEXECUTEINFO	lpExecInfo;
PROCESS\_INFORMATION processInfo;
DWORD				dwExitCode;
HANDLE				hProcess = 0;
BOOL				bResult;
LPTSTR				strCmd;





strCmd = \_T("");

//bResult = StartupApplicationWithShell (\_T("LiveUpdate.exe"), (LPTSTR)strCmd,  GetSafeHwnd(), &hProcess);
bResult = StartupApplicationWithProcess (\_T("C:\\\\Windows\\\\notepad.exe"), (LPTSTR)strCmd,  &processInfo);

EnableWindow(FALSE);



if(bResult) { //(UINT)result > HINSTANCE\_ERROR)

	//ShowWindow( SW\_HIDE );
	//ShowWindow( SW\_SHOWNOACTIVATE );
	

    //WaitForSingleObject( hProcess, INFINITE );
	WaitForSingleObject(processInfo.hProcess, INFINITE);
	//WaitForMultipleObjects(1, &processInfo.hThread, TRUE, INFINITE );



	   
	//if (!GetExitCodeProcess(hProcess, &dwExitCode)) {
	//	   	AMLOGINFO(\_T("LiveUpdate is not terminated normally.")); 
	//}
	if (!GetExitCodeProcess(processInfo.hProcess, &dwExitCode)) {
		   	//failed
	}
	CloseHandle( processInfo.hProcess );
    CloseHandle( processInfo.hThread );
	//CloseHandle(hProcess);


} else {
	
	// failed
}

BringWindowToTop();
EnableWindow(TRUE);

//UpdateWindow();

//::SetWindowPos( GetSafeHwnd(), HWND\_TOP, 0, 0, 0, 0, SWP\_NOMOVE | SWP\_NOSIZE | SWP\_SHOWWINDOW );

}

sdancer75

[Victor Nijegorodov]

Maybe this will help you: windows forceforeground (bringWindowToTop) brings it to top but without being active (a forceForeGround that works with windows xp and windows 7) | Roger's woze[^]

[sdancer75]

I will give it a try but as you may already see, I am using the bringWindowToTop without success. Thanx

sdancer75

[Jochen Arndt]

My intention was to show you a solution that differs from your current implementation and pointing to the fact that you block the message loop. You must not call WaitForSingleObject from within your main thread to ensure that the window is repainted (e.g. when moving another window over the application window). That will solve the problem of paint corruption and might also solve your other problems. Overall I think I must shout: Don't use WaitForSingleObject from within your main GUI thread; especially with long wait times! I (like most others here) will not download a complete project and build it. Especially in this case where it must be tested with XP too.

[Victor Nijegorodov]

Yes, I see. But try it in the following order: EnableWindow SetForegroundWindow SetActiveWindow BringWindowToTop

[sdancer75]

Thanks for your time. Do you suggest to use WaitForMultipleObjects instead ?

sdancer75

[sdancer75]

Seems to work with one exception. I get a flicker since it instantly lose its focus and then regain it back....

sdancer75

[Jochen Arndt]

No. That is similar (it can just wait for more events). Don't use any blocking wait (or more general: any function that may block for long intervals) from within the main GUI thread. As already suggested you might use a worker thread.

[sdancer75]

The worker thread does not lock the main app as long as its active. I dont want this. I just want a modal like behaviour and not floating windows all around the desktop.

sdancer75

[sdancer75]

One last thing. The EnableWindow(xxxx) do the mess in my situation. If I dont use this function I have to process the paint messages from the child window. In this case I think that

WaitForMultipleObjects

will do the job in the XP case. Do you agree with this guess ? .... or better i will give it a try right now.

sdancer75