NetNews Usenet Archive 1992 #20/NN_1992_20.iso/spool/comp/sys/mac/programm/15235

Internet Message Format | 1992-09-09 | 1.6 KB

Path: sparky!uunet!mcsun!uknet!qmw-dcs!jeremyr
From: [e-mail] (Jeremy Roussak)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Patching the _Launch Trap
Message-ID: <[e-mail]>
Date: 9 Sep 92 17:21:36 GMT
References: <[e-mail]> <[e-mail]> <[e-mail]>
Sender: [e-mail] (Usenet News System)
Organization: Computer Science Dept, QMW, University of London
Lines: 22
Nntp-Posting-Host: sequent.dcs.qmw.ac.uk

In <[e-mail]> [e-mail] (Keith Rollin) writes:

>I do something like this. I patch InitGraf right now, but I'm considering a
>scheme where I patch InitAllPacks, instead. The problem with patching InitGraf
>is in determining if the call is being made from the start of an application.
>Some InitGraf calls are made from INITs at INIT time (by ShowINIT, for example);
>some applications call InitGraf more than once (applications written with THINK
>Pascal are common "offenders"); and CE Toolbox calls InitGraf at shutdown time
>under certain circumstances. If you patch InitGraf, you'll have to look out for
>all these cases.

The other problem with patching _InitGraf is that it doesn't
move memory, so neither can (should) your patch. We won't get
into the "all traps move memory because of patches" here! You
can argue that unexpectedly moving memory within _InitGraf
probably won't matter because of the way in which apps call it,
but it's a little unsafe. _InitFonts, on the other hand, does
move memory and is usually called immediately after _InitGraf.

When is _InitAllPacks called?

Jeremy