SOLUTION: handling GUI resource locks between event handler and boost::thread

Hey Paavo,

I'll have to chew a bit on your example, doesn't seem so obvious to me -
I haven't yet learned even nearly all aspects of C++.
Put it in my "re-read" folder :)

Meanwhile, I managed to solve my locking problem with the help of input
from this thread, in the way stated below.

Best Regards & thanks to everyone involved,

    Lars

solution relevant code excerpt (missing includes and wxWidgets
initialization):
/* *** */

debuggingGUImainFrame *mainWindow; // wxWidgets main window,
// controls cmd1 (wxButton) and txt1 (wxTextCtrl)

int glbSERVICING = 0; // "keepalive flag" for the background thread

// mutex to ensure alternate access to window controls and glbSERVICING
boost::mutex mutexChecka;

typedef boost::mutex::scoped_lock lockaChecka;

void demonstrateFrameLock()
{
   sleep (1);
   cout << "child thread: acquiring lock" << endl;
   lockaChecka lc (mutexChecka);
   cout << "child thread: got lock, child thread: ready for servicing"
<< endl;
   mainWindow->cmd1->Enable();

   int i = 0;
   while (glbSERVICING) {
     lc.unlock(); // unlock r/w access to keepalive flag
     cout << "child thread: unlocked" << endl;
     ++i;
     sleep (2);
     cout << "child thread: servicing... (i = " << i << ")" << endl;
     lc.lock(); // prepare read access to keepalive flag
     cout << "child thread: got lock" << endl;
   }

   cout << "child thread: mainWindow->txt1->GetValue = " <<
mainWindow->txt1->GetValue() << endl;
   mainWindow->cmd1->Enable();

   lc.unlock();
   cout << "child thread: unlocked, thread finished" << endl;
}

void debuggingGUImainFrame::OnToggle( wxCommandEvent& event )
{
   cmd1->Disable();

   cout << "main thread: acquiring lock" << endl;
   lockaChecka lc (mutexChecka);
   cout << "main thread: got lock" << endl;

   if (glbSERVICING) {
     glbSERVICING = 0;
     mainWindow->cmd1->SetLabel (wxT ("Enable Service"));
   }
   else {
     glbSERVICING = 1;
     mainWindow->cmd1->SetLabel (wxT ("Disable Service"));
     boost::thread *helperThread;
     helperThread = new boost::thread(&demonstrateFrameLock);
     delete helperThread;
     helperThread = 0;
   }

   cout << "main thread: unlocking" << endl;
   lc.unlock();

   cout << "main thread: thread finished" << endl;
}
/* *** */