c++ - QApplication In Non-Main Thread

Question

I need to exec() a QApplication in a thread that is not main (my GUIs must be plugins that can be dynamically loaded and unloaded at runtime, so I have no access to the main thread). Does anyone know of a (relatively) painless way to hack around Qt's restriction against starting QApplication outside of main?

I'm developing in Linux with Qt4 in C++ using gcc4.3.4.

Answer 1

You can start a QApplication in a PThread as below

//main.cpp

#include <iostream>
#include "appthread.h"
int main(int argc, char *argv[]) {
  InputArgs args = {argc, argv};
  StartAppThread(args);
  sleep(10);
  return 0;
}

//appthread.h

struct InputArgs{
  int argc;
  char **argv;
};
void StartAppThread(InputArgs &);

//appthread.cpp

#include <QApplication>
#include <QMainWindow>
#include <QPushButton>
#include "appthread.h"
#include <pthread.h>

void *StartQAppThread(void *threadArg) {
  InputArgs *args = (struct InputArgs*) threadArg;
  QApplication app(args->argc, args->argv);
  QMainWindow w;
  w.show();
  w.setCentralWidget(new QPushButton("NewButton"));
  app.exec();
  pthread_exit(NULL);
}

void StartAppThread(InputArgs &args) {
  pthread_t thread1;  
  int rc = pthread_create(&thread1, NULL, StartQAppThread, (void*)&args);
}