Program Doesn't Terminate Correctly

I'm writing a computer vision app (C++ and OpenCV). I am creating a GUI for it with wxWidgets - this is very simple; a button-press event calls the tracker app to begin.

My call to terminate the app (i.e. on clicking to close button) is as follows:

// Exiting the App
void MyFrame::OnQuit(wxCommandEvent& WXUNUSED(event))
{
    // true is to force the frame to close
    Close(true);
}

This usually works with more trivial GUI apps. However, on this occasion, the frame disappears yet, in the task manager, the process seems to continu开发者_Go百科e running and holding memory. It's very annoying because if I run or debug the application and later make some changes and try to run again, without manually terminating the process beforehand, the compiler throws a link error because the .exe is

not found or not built by the last incremental link.

Tried inserting a brute force exit(1); in the onQuit method but it causes the app to crash.

I'm not sure what it is.. when running without the GUI, the app runs and terminates fine (albeit it is called slightly differently - from the main() function instead of from a button-press event handler which calls an abstract base class).

Is it possible that it is because a class is being declared with global scope? As in, in one file I have an instance of a class declared outside of any class method? Perhaps wxWidgets can't handle this?

To clarify:

The frame I'm closing is a top level frame. I had no problems with the exact same GUI code when it does not call the computer vision methods.

I haven't specifically coded any multi-threading but to begin with, I was getting an error that said "Error: Cannot initialize OLE". To fix this, I had to set wxUSE_DRAG_AND_DROP, wxUSE_CLIPBOARD, wxUSE_OLE and wxUSE_OLE_AUTOMATION to 0 (instead of 1) and then (re)compile wxWidgets.

Just wondering, is there some kind of threading going on with HighGUI that is inconsistent with WxWidgets? Has anybody else encountered similar problems?

::wxExit

void wxExit()

Exits application after calling wxApp::OnExit. Should only be used in an emergency: normally the top-level frame should be deleted (after deleting all other frames) to terminate the application. See wxCloseEvent and wxApp.

Include files

<wx/app.h>

You can also simply call the crt function exit() which will instantly shut down everything.

However, if you want to more polite than these rather brutal methods ( which you may want to do in particular if you have placed some special shut down code in wxApp::OnExit ) then you want to find the top level window and close that. To do this from anywhere in your code

wxGetApp().GetTopWindow()->Close()

Thanks for all the help, I have solved the problem. Seems fairly obvious now but couldn't figure it out at the time!

Originally, my computer vision app was called from a main function. However, with the new GUI code there is no need for a main so I replaced the original main with a shell class.

Though I had been careful to free allocated memory within the methods of my computer vision classes I had not been so careful with the original main function because once that function ended, all memory previously in use would be cleared up by the program's regular exiting.

The difference with the new GUI code is that when the shell class is finished - the program is still running. The clue was in the fact that even when the computer vision app had ended, the blue light on my webcam was still shining.

* Be sure to call cvReleaseCapture( &capture ); to free up that thread and release the hardware *

Your call to Close only closes the frame, but doesn't stop the application, because it is not the last top level window. The wxWidget contains a topic Window Deletion Overview. It states that

A wxWidgets application automatically exits when the last top level window (wxFrame or wxDialog), is destroyed. Put any application-wide cleanup code in wxApp::OnExit (this is a virtual function, not an event handler).

Is your frame the top-level frame? If not, you may have to call Close or Destroy on a top-level frame.