Re: GS/OS Hires/Double-Hires File Recognition Problem

[nathan@cco.caltech.edu (Nathan Mates)]

In article <4bjcqv$r93@newsbf02.news.aol.com>,
RUBYWAND <rubywand@aol.com> wrote:
>In article <DK2HqA.787@actrix.gen.nz>, dempson@atlantis.actrix.gen.nz
>(David Empson) writes:
>>In summary: if an application is not recognising a picture because the
>>file size is "wrong", then it is the fault of the application, not the
>>system software.

>    One might expect this to be the case. Nevertheless, I was able to get
>Platinum Paint to accept $1FF8 size hires files by patching Tool 23 under
>GS/OS 5.04. (Unfortunately, System 6.0.1's Tool 23 is quite a bit
>different.)  It seems clear that Platinum Paint is accessing some standard
>file I/O routine which has to do with Tool 23.

   Tool 23 is the tool that helps put up the Open/Save dialog box.
It is not part of GS/OS, but calls many GS/OS calls to do the work.
Reading the documentation for the open call, you can provide a list
of file/auxtypes that will be displayed in the dialog box. This list
is provided _by the application_, and not by GS/OS. 

   Further, you can set up callback procedures to your own code (a
"filter" procedure) that'll accept or deny files based on any
characteristics you choose to program in. This is apparently what PP
does-- it gives the thumbs up or down to each file based on
length. When you patched the 5.0.4 Tool 23, I'd bet you forced a
thumbs up for all files. That's not the problem of the OS, that's the
application once again.

>    Regarding file identification, there is no way to guarantee that any
>file is a hires pic. Using Length = $2000 and filetype = BIN is a fair
>try. Alas, since most hires pics are length $1FF8, it is an inadequate
>try. The routine needs to be fixed to accept $1FF8 - $2000 length files.  

   "Most" files are L=$1FF8? Maybe to you, but not to the authors of
PP. As David said above, it's not the fault of Tool23 that files are
being rejected, it's the callback to PP's filter procedure. I'm on
vacation at my parent's house until the end of the month, but would be
willing to bet that this is the case by tracing the relevant tool calls
and all their parameters. 

   (In reading the docs for the Open dialog box routine, you cannot
pass a list of "Apple II picture files only" that includes BIN files
by length.  If you are using a custom filetype (one of those ones
Apple defined a long time ago, but nobody ever bothered with), then it
just might be in Tool 23's realm to accept/deny based on length, but
that cannot be true with BIN files)

Nathan Mates
-- 
<*> Nathan Mates http://www.ugcs.caltech.edu/~nathan/      <*>
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