Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.csd.uwm.edu!gem.mps.ohio-state.edu!ginosko!husc6!sunfs3!kent
From: kent@sunfs3.camex.uucp (Kent Borg)
Newsgroups: comp.sys.mac.programmer
Subject: Re: System 7.0 & Aliases
Message-ID: <488@sunfs3.camex.uucp>
Date: 24 Aug 89 16:27:37 GMT
References: <227700026@uxa.cso.uiuc.edu> <483@sunfs3.camex.uucp> <9173@thorin.cs.unc.edu> <13784@shamash.cdc.com> <490@sunfs3.camex.uucp> <30837@ucbvax.BERKELEY.EDU>
Reply-To: kent@sunfs3.UUCP (Kent Borg)
Organization: Camex, Inc., Boston, Mass USA
Lines: 47

In article <30837@ucbvax.BERKELEY.EDU> oster@dewey.soe.berkeley.edu.UUCP (David Phillip Oster) writes:
>In article <490@sunfs3.camex.uucp> kent@sunfs3.UUCP (Kent Borg) writes:
>>`Aliases', as they are calling them, are implemented as a
>>little file which has the volume name and file id (itself a new 7.0
>>feature) of the actual file.
>
>Note, this means that your Save command had better write the data back 
>into the original file, and not into some newly created file that it will
>rename if the write succeeds. (if it destroys the original in the course
>of the save, it will disconect any aliases that file might have.)
>
>How many programs do a delete before the save? How many don't catch the
>fact that delete uses the poor man's search path, so if you try to create
>a document named "Finder" a side effect is to delete the Finder?
>
>Programmer beware! Programer take care!

As I understand it, aliases are implemented as a charade put on by the
standard file dialogs and the Finder.  

When user says "Open...", and in the open file dialog selects an alias
file, then clicks "OK", the reply record will be filled in with the
details of the *actual* file (mounting a needed AppleShare volume if
needed), as if the user had actually gone and opened that file.  The
application never sees the alias file or its directory.

The Finder will do about the same.  If the user double clicks on an
alias file, the Finder will find the real thing and pass info about it
to the application.

(I don't know about icons for aliases.  I guess that they might be
just like the icon of the actual file, but with some regular adornment
like a gray drop shadow??)

One problem I see with aliases will be for people who have hacked the
standard file dialog.  What if you want to access the file in a hook
routine?  Maybe you are displaying a thumbnail sketch of a large image
and need to look at a low resolution version you left in a resource.
What will you see at hook time?

Will delete still use the Poor Man's Search Path?  I don't know.  I do
know that Apple is working very hard to not break old programs.

Kent Borg
kent@lloyd.uucp
or
...!husc6!lloyd!kent