First call is WM_PAINT or WM_CREATE ?

! NOT; true if its argument is false

1 fFlipFlop is declared FALSE
2 then its changed to TRUE
3 so it should call the first argument (black) but it calls FALSE (white) for the first time.

Is it because Windows first calls WM_PAINT and then WM_CREATE ?

Code:

/*-----------------------------------------
   BEEPER1.C  -- Timer Demo Program No. 1
                 (c) Charles Petzold, 1998

  -----------------------------------------*/

#include <windows.h>

#define ID_TIMER    1

LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
     static TCHAR szAppName[] = TEXT ("Beeper1") ;
     HWND         hwnd ;
     MSG          msg ;
     WNDCLASS     wndclass ;
     
     wndclass.style         = CS_HREDRAW | CS_VREDRAW ;
     wndclass.lpfnWndProc   = WndProc ;
     wndclass.cbClsExtra    = 0 ;
     wndclass.cbWndExtra    = 0 ;
     wndclass.hInstance     = hInstance ;
     wndclass.hIcon         = LoadIcon (NULL, IDI_APPLICATION) ;
     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
     wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
     wndclass.lpszMenuName  = NULL ;
     wndclass.lpszClassName = szAppName ;
     
     if (!RegisterClass (&wndclass))
     {
          MessageBox (NULL, TEXT ("Program requires Windows NT!"), 
                      szAppName, MB_ICONERROR) ;
          return 0 ;
     }
     
     hwnd = CreateWindow (szAppName, TEXT ("Beeper1 Timer Demo"),
                          WS_OVERLAPPEDWINDOW,
                          CW_USEDEFAULT, CW_USEDEFAULT,
                          CW_USEDEFAULT, CW_USEDEFAULT,
                          NULL, NULL, hInstance, NULL) ;
          
     ShowWindow (hwnd, iCmdShow) ;
     UpdateWindow (hwnd) ;
          
     while (GetMessage (&msg, NULL, 0, 0))
     {
          TranslateMessage (&msg) ;
          DispatchMessage (&msg) ;
     }
     return msg.wParam ;
}

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
     static BOOL fFlipFlop = FALSE ; //declared FALSE
     HBRUSH      hBrush ;
     HDC         hdc ;
     PAINTSTRUCT ps ;
     RECT        rc ;
     
     switch (message)
     {
     case WM_CREATE:
          SetTimer (hwnd, ID_TIMER, 1000, NULL) ;
          return 0 ;

     case WM_TIMER :
          MessageBeep (-1) ;  
          fFlipFlop = !fFlipFlop ;    // changed to TRUE
          InvalidateRect (hwnd, NULL, FALSE) ;
          return 0 ;
          
     case WM_PAINT :
          hdc = BeginPaint (hwnd, &ps) ;
          
          GetClientRect (hwnd, &rc) ;

          hBrush = CreateSolidBrush (fFlipFlop ? RGB(0,0,0) : RGB(255,255,255)) ;
          // so here its being true, it should call RGB(0,0,0) (black) but it calls (white)

          FillRect (hdc, &rc, hBrush) ;

          EndPaint (hwnd, &ps) ;
          DeleteObject (hBrush) ;
          return 0 ;
          
     case WM_DESTROY :
          KillTimer (hwnd, ID_TIMER) ;
          PostQuitMessage (0) ;
          return 0 ;
     }
     return DefWindowProc (hwnd, message, wParam, lParam) ;
}

When I run it, I get white before the first beep happens -- so for the first second, until WM_TIMER happens, fFlipFlop is still false. Is this not what you expected?

I get white too so it means that it calls WM_PAINT first and then WM_CREATE.

I thought Windows calls WM_CREATE first as the CreateWindow() function in WinMain causes WM_CREATE message.

PS i dont get bip cause i dont know how to make it work in VC++ 2008.

I think you're still missing the point: neither WM_PAINT nor WM_CREATE changes the value of your boolean -- only WM_TIMER does. Regardless of which one happens first, they're both going to get called before WM_TIMER (since that takes an entire second).

PS: To make the beep work in Visual C++, you ... don't do anything. (I mean, I didn't do anything, and there it is.) It is in gdi32.lib, but if it wasn't linking with the library you'd get linking errors. Maybe take your speakers off mute?

I know that it is changed in WM_TIMER but WM_TIMER is called by SetTimer (hwnd, ID_TIMER, 1000, NULL) which is in WM_CREATE. So it must be called after WM_PAINT.

WM_PAINT --> WM_CREATE --> WM_TIMER

PS ok i found reason. I chose "no sound" in Control Panel/ Sounds and Audio Devices.
Thanks for making me think of it.

But the timer is set to start 1000ms after the creation of it, so flipflop isn't being changed until 1 second after WM_PAINT being called.

Perhaps you would be better off opening a file and then logging the relevant stuff. Something along these lines:

Code:

// At beginning of file somewhere
#include <time.h> 
#include <stdio.h>
FILE *logfile;  // Make this a global variable. 
...
// In winMain:
     WNDCLASS     wndclass ;

    logfile = fopen("c:\\logging.txt", "w");
     
     wndclass.style         = CS_HREDRAW | CS_VREDRAW ;
...
// at end of winMain:
    fclose(logfile);
// Then add something like this in relevant places:
     fprintf(logfile, "%6.2f Recieved VM_xxxx\n", clock() / (double)CLOCKS_PER_SEC);

The time will be printed in seconds (with hundreds of a second precision), which should make it perfectly clear what is going on and in which order. I find it very unlikely that a WM_PAINT would precede the WM_CREATE, since before the window is create, there is nothing sensible that can be painted and it serves no purpose to do so - it's like filling the forecourt of a petrol station with petrol, because you didn't have a car, but you thought it was a good idea to fill up anyways... ;-)

--
Mats

Thanks Mats, it makes perfect sense.

I'll try to create this logfile, it indeed will help me to see it better too.

Test using a MessageBox or break point in the event handlers .

Part of creating a window is painting it to the screen (ie generating a WM_PAINT)

So

WM_CREATE (or WM_INITDIALOG)
WM_PAINT (and WM_SIZE, WM_NCPAINT, WM_ERASEBKGND etc)
... appox 1 sec later (and lots of msgs)
WM_TIMER
WM_PAINT

EDIT: WM_TIMER are the lowest priority msg in the apps queue (of default 8 msgs). They will be ignored in favour of other msgs (which is why timers have a min accuracy of +/- 50ms).