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Re: hilighting

>I'm trying to figure out how to hilight an object using the hilite
>mode described in IM V, 61-62.  It says:
>"There are two ways to use hilite mode.  The easiest is to call
>    BitClr (Ptr(HiliteMode,pHiliteBit))
>just before calling InvertRect..."
>On the next page it says:
>"The constants used with hilite mode are listed below:
>    hilite     = 50;
>    pHiliteBit = 0;"
>Well, I couldn't figure this out, so I searched files for "hilite" and
>found this example, in MCL:library:Inspector
>; Invert a region using the highlight color (see Inside Mac V-62).
>(defun %invert-region (rgn)
>  (with-macptrs ((hiliteMode (%int-to-ptr #x938)))
>    (%put-byte hiliteMode (logand #x7f (%get-byte hiliteMode))))
>  (#_InvertRgn :ptr rgn))
>The connection between this code and what IM-V says could use some

Pascal's BitClr procedure numbers bits from the most significant.
Hence the Pascal "pHiliteBit" has a value of 0, whereas the
assembly language "hiliteBit" has a value of 7. I don't know where
"hilite=50" came from. This equate is not in any of my interface files.
I assume it's a manual bug.

The MCL code would probably be clearer if it were written as:

(defun %invert-region (rgn)
  (with-macptrs ((hiliteMode (%int-to-ptr #$HiliteMode)))
    (%put-byte hiliteMode
               (logand (lognot (ash 1 #$hiliteBit)) (%get-byte hiliteMode))))
  (#_InvertRgn :ptr rgn))