Cycle of processing / processing mouse messages

I wrote a multi-threaded program that does some thinking and outputs some diagnostic data along the way. I noticed that if I shake my mouse while the program is running, the program will run faster. Now I could go into detail about exactly how I type ... but I will stick in place because I noticed that in many other programs everything happens faster if the mouse moves, I wonder if this is some classic error that produced many people in which the message loop is somehow slowed down by a moving mouse.

EDIT: my "print" method looks like this ... I have an advanced edit control window for displaying text. When I want to print something, I'll add new text to the existing text inside the window and then redraw the window using SendMessage (, WM_PAINT, 0,0).

It's actually a little more complex, I have several rich edit control windows, one for each thread (4 threads on my 4-core PC). A rough outline of my "my_printf ()" looks like this:

void _cdecl my_printf(char *the_text_to_add)
{
    EnterCriticalSection(&my_printf_critsec);
    GetWindowText(...); // get the existing text
    SetWindowText(...); // append the_text_to_add
    SendMessage(...WM_PAINT...);
    LeaveCriticalSection(&my_printf_critsec);
}

      

        
        
        
      

    

I must point out that I have been using this printing method for many years in a multi-threaded program without even noticing any mouse interaction.

EDIT: Ok, here is my entire messageloop that runs on the root thread while the child threads do their job. In child threads, my_printf () are reporting their progress.

for(;;)
{
    DWORD   dwWake;
    MSG msg;

    dwWake = MsgWaitForMultipleObjects(
                            current_size_of_handle_list,
                            hThrd,
                            FALSE,
                            INFINITE,
                            QS_ALLEVENTS);

    if (dwWake >= WAIT_OBJECT_0 && dwWake < (WAIT_OBJECT_0 + current_size_of_handle_list))
    {
        int index;
        index = dwWake - WAIT_OBJECT_0;
        int j;
        for (j = index+1;j < current_size_of_handle_list;j++)
        {
            hThrd[j-1] = hThrd[j];
        }
        current_size_of_handle_list--;
        if (current_size_of_handle_list == 0)
        {
            break;
        }

    }
    else if (dwWake == (WAIT_OBJECT_0 + current_size_of_handle_list))
    {
        while (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
        {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
    }
    else if (dwWake == WAIT_TIMEOUT)
    {
        printmessage("TIMEOUT!");
    }
    else
    {
        printmessage("Goof!");
    }
}

      

        
        
        
      

    

EDIT: Solved! It might be an ugly solution, but I just changed the timeout from infinite to 20ms, then in the if (dwWake == WAIT_TIMEOUT) section I changed printmessage ("TIMEOUT!"); for:

while (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
{
    TranslateMessage(&msg);
    DispatchMessage(&msg);
}

      

        
        
        
      

    

I am not closing this question yet, because I would still like to know why the original code was not working on its own.