Re: OnCancel not being called

From:

"Tom Serface" <tom.nospam@camaswood.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Wed, 11 Jul 2007 14:21:11 -0700

Message-ID:

<087652C0-62D9-4D55-9BE7-2ADE913A108F@microsoft.com>

You are probably seeing that the progress control is just swamping the UI.
If you are doing some sort of processing you should do that in a thread and
just send a message to the GUI thread to update the progress. Or, you could
call a function like:

//
// Release main thread for background processing
//
void GiveTime()
{
// Idle until the screen redraws itself, et. al.
MSG msg;
while (::PeekMessage( &msg, NULL, 0, 0, PM_NOREMOVE ) ) {
  if (!AfxGetThread()->PumpMessage( )) {
   ::PostQuitMessage(0);
   break;
  }
}
// let MFC do its idle processing
LONG lIdle = 0;
while (AfxGetApp()->OnIdle(lIdle++ ))
  ;
}

During your loop to allow the GUI to continue to operate.

Tom

<cbdeja@my-deja.com> wrote in message
news:1184178864.431490.199540@o61g2000hsh.googlegroups.com...

I have a progress window which is based on Chris Maunder's
CProgressWnd (which is based on CWnd).

The CProgressWnd window contains a Cancel button with an associated
OnCancel() function which closes the window and sets a member boolean
"has_cancelled" flag.

When I am processing some data I send progress messages to my main
window which then calls a function in CProgressWindow to update its
progress bar. The same function also checks the "has_cancelled" flag
to see whether the user has clicked the Cancel button, and returns
that as a boolean. The main window can therefore tidy up if the user
has pressed the Cancel button.

This works well, but I find that I have to limit the frequency of
progress messages being sent to the main window to less than 5
messages per second.

If I send them any more frequently, pressing the Cancel button seems
to have no effect - the OnCancel() function does not get called. But
the progress bar always updates without a problem.

If I press the Cancel button many times rapidly, then after several
presses the OnCancel function does get called.

This seems bizzare. The message routing is obviously working correctly
because the Cancel button works provided the progress messages are
sent infrequently. Surely the cancel message is getting queued so it
should be calling OnCancel EVERY time the button is pressed.

Does anyone have an idea what is going wrong?