GUI Generators and Class Libraries (was: Better MacOS Handles...

[kilgallen@eisner.decus.org (Larry Kilgallen)]

In article <1996Sep14.150138@nova.wright.edu>, jmatthews@nova.wright.edu (Dr. John B. Matthews) writes:

> I agree. I was particularly intrigued by the potential for tools
> like AppMaker (a GUI-oriented, multi-language code generator from
> Bowers Development) to be adapted to Ada. Another approach would be
> a class library. I'd heard of an effort along this line, but never
> tracked it down. Anybody?

Since I have a lot of experience using AppMaker, I would love to be
able to use it for Ada programs on MacOS.  Templates can be created
by the end-user for AppMaker in addition to the ones supplied for
C* and Pascal, so I expect I will end up doing that.  If so I would
release them for general use sometime after the compiler world got
to the state of being able to build stand-along 68K applications for
Macintosh (that is when it makes business sense for me to spend the
time).  Jim Hopper has indicated he is interested in 68K, but there
are various obstacles.

But I do think that a GUI-generator like AppMaker really fills a
separate need than class libraries.  For Pascal and C, AppMaker will
generate your interface for raw compilation, or for use with the
MacApp or TCL class libraries (you have to specify at the start
which type of output you want).  When your GUI has been generated
to use a class library you respect, maintenance is much easier.

In looking at potential Macintosh class libraries, MacApp seemed to
stand out for keeping up to date with the latest Apple features, and
I thought I would possibly have to transliterate MacApp to Ada.  Jim
Hopper told me, however, that GNAT for Macintosh allowed Ada programs
to subclass C++ classes, meaning transliteration could be deferred and
MacApp could be used right away.  I have not tried this, but it sounds
reasonable.

There has been some talk about a portable Ada class library for
GUIs, but I am skeptical that anything covering multiple operating
systems can get all the nits of each correct.  Macintosh users expect
Balloon Help to be covered, along with hooks to Apple Guide.  Unix
users expect the new Common Desktop features associated with saving
application state to be there.  OS/2 users expect _their_ particular
set of right-mouse-button actions to be implemented.  I am skeptical
that platform-agnostic Ada zealots could match the performance of
language-agnostic-but-stuck-with-C++ platform zealots in meeting the
GUI requirements of the True Believers in various platforms. for that
reason, I am interested in good Ada bindings to, and eventually good
Ada implementation of, a well-designed MacOS class library.  Rewriting
MacApp in Ada might not be hard, but distributing the results involves
Apple's intellectual property.  Since they give away the C++ version,
they certainly don't view MacApp as a revenue source, but probably rather
a way to help folks develop for MacOS, so even getting them to distribute
an Ada version might be possible.

That's my take, but if someone has a different approach don't let
my enthusiasm be a deterrent to following another path as well.

Larry Kilgallen
LJK Software