Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!asuvax!ukma!psuvax1!psuvm!f0o
From: F0O@psuvm.psu.edu
Newsgroups: comp.lang.pascal
Subject: Problem with the WVSPrintF function
Message-ID: <91156.113452F0O@psuvm.psu.edu>
Date: 5 Jun 91 15:34:52 GMT
Organization: Penn State University
Lines: 42

Hi netters!

   I'm new to Windows programming and I was trying to modify the
STEP3.PAS example program that comes with TPW.  I was changing the
WMLButtonDown method.  The original routine looks like this:

Procedure TMyWindow.WMLButtonDown(Var Msg:TMessage);
VAR
  DC: HDC;
  S: array[0..9] of char;
BEGIN
  WVSPrintF(S, '(%d,%d)', Msg.LParam);
  DC := GetDC(HWindow);
  TextOut(DC, Msg.LParamLo, Msg.LParamHi, S, StrLen(S));
  ReleaseDC(HWindow, DC);
END;

   This of course works fine, but I modified the code in the following
way so I could print some text instead of a number:

Procedure TMyWindow.WMLButtonDown(Var TextString: PChar);
VAR
  DC: HDC;
  S: PChar;
BEGIN
  WVSPrintF(S, '%s', TextString);
  DC := GetDC(HWindow);
  TextOut(DC, Msg.LParamLo, Msg.LParamHi, S, StrLen(S));
  ReleaseDC(HWindow, DC);
END;

   When Windows hits the WVSPrintF statement, I get a UAE.  By running
in the debugger, the UAE is reported as exception code 13, a memory
addressing error.
   The problem must be that I'm not using PChar correctly, although
the on-line help states all parameters of WVSPrintF are of type PChar
and the manual shows examples of where you can put a text string into
a variable of type PChar.
   If someone can tell me what I'm doing wrong, I'd greatly appreciate
it!

                                                      [Tim]