resource - .h file:

#define CustomAlert 1000

resource - .rcp file:

ALERT ID CustomAlert
BEGIN
  TITLE "custom alert"
  MESSAGE "^1\n^2\n^3"
  BUTTONS "OK"
END

code:

    Char alertMsg[64];
    StrPrintF(alertMsg, "Your value is %d", yourValue);
    FrmCustomAlert(CustomAlert, alertMsg, "", "");

do NOT pass NULL value as param in FrmCustomAlert - always use "".

Boolean SetScreenColorDepth(int depth)
{
    UInt16 reqDepth=depth;
    Err err = WinScreenMode(winScreenModeSet,NULL,NULL,&reqDepth,NULL);
    return !err;
}

Boolean RestoreScreenColorDepth(void)
{
    Err err = WinScreenMode(winScreenModeSetToDefaults,NULL,NULL,NULL,NULL);
    return !err;
}

You must set color depth before any window is created. Check error codes for unsupported modes.

This is an example, how to do and use double buffering (offscreen window) to create smooth animations

WinHandle displayWindow;
WinHandle offscreenWindow;

void CreateOffScreen() {
    Err err;
    offscreenWindow = WinCreateOffscreenWindow(160,160, screenFormat, &err);
}

void PaintOffScreen() {
    WinSetDrawWindow(offscreenWindow);
    // draw there
}

void Show() {
    RectangleType bounds;

    WinSetDrawWindow(displayWindow);
    WinGetBounds(displayWindow, &bounds);
    WinCopyRectangle (offscreenWindow, 0, &bounds, 0, 0, 0);
}

I've bought brand new IBM. It's marvellous and I'm trying to install my favourite OS now.

Updated: all my wishes succeeeeeeded :) It's GREAT