WM_SETFONT = &H30

This material does provide the answer. However I thought that a very simple piece of sample code would help others understand how to change a default font on a control.

BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
  hWnd = CreateWindow(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
		    120, 40, 400, 400, NULL, NULL, hInstance, NULL);
  if (!hWnd)
  {
    return FALSE;
  }
// Set the font for all buttons etc: 
  hFont=CreateFont (14, 0, 0, 0, FW_DONTCARE, FALSE, FALSE, FALSE, ANSI_CHARSET, \
		  OUT_DEFAULT_PRECIS, CLIP_DEFAULT_PRECIS, DEFAULT_QUALITY, \
		  DEFAULT_PITCH | FF_SWISS, L"Arial");

// Create our control:
  hBtnButton1 = CreateWindow (L"BUTTON", L"Button1", \
		  WS_CHILD | WS_VISIBLE | BS_PUSHBUTTON | BS_CENTER, \
		  10, 10, 50, 25, hWnd, (HMENU) IDR_BUTTON1, hInst, NULL);
  if (hBtnButton1 == NULL)
  {
    MessageBox (hWnd, L"hBtnButton1 not created", L"Create hBtnButton1", IDOK);
  }

// Set the new font for the control:
  SendMessage (hBtnButton1, WM_SETFONT, WPARAM (hFont), TRUE);

  ShowWindow(hWnd, nCmdShow);
  UpdateWindow(hWnd); 
  return TRUE;
}

Kenneth Spencer

The font object whose handle is passed in the wParam parameter must live at least as long as the control that is sent the message does. You must not delete this font until either a) you destroy the control, or b) set a different font by sending WM_SETFONT again.

The control will use this handle directly in its WM_PAINT handling (by passing it to SelectObject) and strange behaviour will occur if the object has been deleted. If the handle has been reused you might get a different font, or it might point to a different type of GDI object altogether, causing other painting errors.

It is permissible to use the same font object with multiple controls, as long as the font object's lifetime is at least as long as the longest-lived control. You could, for example, create the font object during program startup and retain it for the full lifetime of the program.