Updating ListBox during lengthy operation

Through WM_COMMAND i call a function that will process something and put out results to a listbox.

Im trying to call

Code:

  
// inside the lengthy function
while(PeekMessage (&msg, NULL, 0, 0, PM_REMOVE))
{
        if (msg.message == WM_QUIT)
            break;
        TranslateMessage (&msg) ;
        DispatchMessage (&msg) ;
}

    UpdateWindow(hWnd);
    RedrawWindow(hWnd, 0, 0,
                 RDW_INVALIDATE | RDW_ERASE | RDW_ERASENOW | RDW_UPDATENOW);

to update the listbox but apparently its not enough or I dont call PeekMessage the right way.
I dont know where should i put PeekMessage?
Right now I use GetMessage also in WinMain.

Try changing the RedrawWindow() to an InvalidateRect() followed by an UpdateWindow(). This combo generates a WM_PAINT msg but posts it directly to the HWNDs callback (bypassing the msg queue). Also remove the PeekMsg pump.

I generally use a worker thread to do lengthy operations and use PostMessage() to send UI updates to the main thread. This ensures my UI remains responsive.
If you want to get complicated register a HWND_BROADCAST msgs (or similar) to send the ListBox items to the main thread and have the main thread add them to the control.

Part of your problem is that DispatchMessage() blocks until the message has been processed. As you are generating msgs (ie WM_ERASEBKGRND ) your PeekMsg will always be finding new msgs to process.

Using Messages and Message Queues

Thanks Novocain!

With a workerthread its working well.
Also your other advices will serve me in the future.