Re: A Messageloop problem

>From: "C.G.W. van Zeeland" <cees_van_zeeland_at_compuserve.com>
>
>I am doing some Forth exercises with Petzolds examples.
>( Programming Windows: Chapter 5 - Random Rectangles )
>I struggled with the Dispather

while (TRUE)

{
     if (PeekMessage (&msg, NULL, 0, 0, PM_REMOVE))
     {
          if (msg.message == WM_QUIT)
               break ;

          TranslateMessage (&msg) ;
          DispatchMessage (&msg) ;
     }
     else
          DrawRectangle (hwnd) ;
}
return msg.wParam ;

Cees,

Perhaps a better translation of the message loop is

: MSGLOOP ( -- res ) BEGIN
      PAD 0 0 0 PM_REMOVE PeekMessage IF
         PAD CELL+ @ WM_QUIT = IF
            PAD 2 CELLS + @ EXIT
         THEN
         PAD TranslateMessage DROP
         PAD DispatchMessage DROP
      ELSE DrawRectangle THEN
   AGAIN ;

Or, if you object to the exit in the middle:

: MSGLOOP ( -- res ) BEGIN
      PAD 0 0 0 PM_REMOVE PeekMessage IF
         PAD CELL+ @ WM_QUIT <> DUP IF
            PAD TranslateMessage DROP
            PAD DispatchMessage DROP
         THEN 0=
      ELSE DrawRectangle 0 THEN
   UNTIL PAD 2 CELLS + @ ;

but I find the second variation harder to read because
it has to carry a flag around instead of acting immediately
when the exit condition is detected.

Hope this helps!

Rick VanNorman

.
Received on Sun May 21 2000 - 10:06:41 PDT