wags@cimage.com (Bill Wagner) (03/08/91)
Thanks for all the responses to XVT. Here is the summary of the
information I received.
XVT seems to lie somewhere between a union of and the intersection of
the GUIs they support. Where "union" is the appropriate term, XVT
seems to have filled in the holes themselves.
Our evaluation leads us to believe that XVT will be useful for
prototyping apps on the various platforms supported. We find it
limiting in terms of providing a complete "look & feel", and we
would need to cirmcumvent it in order to develop a quality product.
Users seem to feel it more closely resembles the Mac interface
than either MS-Windows, or Motif.
There are no widgets in XVT, and no corresponding entity. The
toolkit is very much like the Mac in that, for the most part, it
is fairly low-level, and if there are any 'extras' they, too have
been written using XVT, not the native toolkit. As far as
'pushing the envelope', it just turns out that there are things
available in Motif or the Athena Widgets that you have to write
yourself in XVT, but this can be done.
There is a mailing list related to XVT questions and info (apparently
there is little activity at this time):
info-xvt-request@presto.ig.com
There is a Dutch firm that specializes in development and support
of XVT apps on various platforms. They also organize training
courses directed to the development of XVT applications:
Paul Veger
Decos Software Engineering BV
Sandtlaan 36
2223 GG Katwijk
The Netherlands
+31 1718 51403
PROS:
It does seem to reduce development time for standard products,
and does allow for manual operation where non-portable entities
(such as timer events) are needed.
Pass-through mode does allow the programmer to use missing
primitive widgets.
CONS:
You are still abandoning full font control, internationalization,
all geometry management other than bulletin boards (and thus you
lose user-font control), and a number of other features.
The pass through mode may allow you to use missing primitive
widgets (e.g. arrow button) however there is no way to use composite
widgets, since there is no way to create XVT objects as children of
those widgets.
Some summary Comments from knowledgable folks:
(consider these opinions)
(not from the same person)
Virtual toolkits are too limiting and that any commercial app will
have to bypass them at one point or another. (A quick survey of
about 17 of the apps on my Mac shows that only one does not have
some non-standard, application-specific interface object).
I do know that there is no way in hell I could have written <product name
deleted> in XVT without going through to the Motif/Xt level.
Some of those cases would be due to dealing with Motif bugs/limitations,
others just a matter of trying to make the interface more usable; I'm
a firm believer in tuning each GUI interface individually.
If the speed of porting is more important than the quality of each
individual interface, then as far as I can tell, XVT does work and can
be used.
If all the platforms your are concerned with support X, XVT does not
buy much, if anything. X, and Motif are (should be?) the same on
these platforms.
I do not see how it could ever increase development time on a single
platform unless one insisted on doing something through XVT when a
non-portable approach was indicated.
In summary, I guess I'm saying that I have an extremely sophisticated
user interface designed to manage litterally thousands of data objects
and tens of megabytes of data, and, while using XVT, I haven't had to
compromise at all between the design and the implementation. Maybe if I
were using Motif directly, I would have written less code, but still not
so much less that it would have been easier to write the application
twice, and since I have to support three platforms, that is very
important.
--
Bill Wagner USPS net: Cimage Corporation
Internet: wags@cimage.com 3885 Research Park Dr.
AT&Tnet: (313)-761-6523 Ann Arbor MI 48108
FaxNet: (313)-761-6551mherman@alias.UUCP (Michael Herman) (03/14/91)
I have recently attended an XVT Programming course and am, personally, very impressed with the product and believe that there is great benefit to be derived for (most) any GUI application that needs to run across multiple platforms. Rather than address/correct the specific comments made in the "Evaluation", I think it is more important to understand background of the founders of XVT and the philosophy behind XVT (i.e. to have the "right" frame of mind). The founders come from Bell Labs. Rochkind spent some 12 years there working with all the famous Bell Labs people. Meier has similar experience. Rochkind worked with the people that created the C programming language and when you begin to understand XVT, you'll recognize that the philosophy behind XVT is the same one that made the C programming language successful for creating all sorts of applications across a large variety of platforms. I think the important thing to understand is: "XVT is to native windows systems as C is to assembly language. - Meier" I hope this makes sense and doesn't sound too much like hype. If XVT is to be faulted, I think they could be doing a better job of communicating (read "marketing") this message. Caveat: I have only read through some XVT applications, taken the course and talked (at length) with a couple of the people from XVT. I haven't written any XVT programs. These comments are entirely my own.