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From: rj0z+@andrew.cmu.edu (Robert George Johnston, Jr.)
Newsgroups: comp.sys.mac.programmer
Subject: Hilite Mode Error
Message-ID: <4Y2CH4y00VE1MC7EUf@andrew.cmu.edu>
Date: 27 Feb 89 06:03:48 GMT
Organization: Class of '91, Carnegie Mellon, Pittsburgh, PA
Lines: 33


    In Volume V of Inside Macintosh, on page 61, an explanation of how
to use the Hilite Mode follows:

    There are two ways to use the hilite mode. The easiest is to call
BitClr(Ptr(HiliteMode, pHiliteBit)); just before calling InvertRect,
InvertRgn, InvertArc, InvertRoundRct, or InvertPoly or any drawing using
srcXor mode. On a one-bit-deep destination, this will work exactly like
inversion, and is compatible with all versions of QuickDraw.

    Consider the following Pascal code:
    begin
      PenMode(srcXor);
      BitClr(Ptr(HiliteMode, pHiliteBit));
      FrameRect(SomeRect);
    end;

    On a Macintosh equipped with Color QuickDraw, this procedure acts as
expected, by drawing a rectangle in the current hilite color. If the
screen is only one-bit-deep, it also acts accordingly by inverting the
frame of the rectangle.
    Now, this same code, when executed on a regular SE or Plus without
Color QuickDraw will NOT draw anything to the screen.
    I then discovered that if I set the PenMode to patXor, the procedure
then functions exactly to specifications.

    I have not tried this out on other drawing routines like FrameOval. I
am using Lightspeed Pascal 2.0p1, System Software 6.0.2.

    Perhaps somebody should look into whether the book is wrong or the
implementation is wrong.

    Rob Johnston.