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List:       xul-announce
Subject:    [xul-announce] XUL Titan Interview: Son To (of Sulu fame) - Part I
From:       Gerald Bauer <gerald () vamphq ! com>
Date:       2004-06-18 14:38:25
Message-ID: 20040618143825.29916.qmail () web109 ! biz ! mail ! yahoo ! com
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Hello,

  Welcome back to the XUL Titan Interview series.
Today let's welcome Sulu mastermind Son To.

Q: Can you tell us a little bit about yourself?

Son To: I grew up in Philadelphia, PA and still
currently live there. I've been programming computers
since the age of 10 in a dozen different languages. I
graduated from the University of Pennsylvania's
Wharton School in 2000. I'm currently an independent
contractor working mostly with Java related
technologies. I also teach c#, java, python, linux
classes. I've been an avid linux user since my high
school years (circa 1994). In a previous life, I was
also a unix sysadmin.

I've been a Java programmer since 1995 and use it
primarily for work, but I make an effort to learn a
new language each year because although all languages
are isomorphic in the sense that they're all turing
complete, each languages has a unique way of solving a
given problem in different way. This year my new
language is Prolog ... it has help me understand
semantic web RDF.

Q: How did you stumble onto XUL?

Son To: I stumbled upon XUL via Mozilla around 1999. I
was really excited about XUL when I heard of it
because I like the simplicity of html for quickly
creating GUI forms, but dislike the contortions one
has to go through to create a desktop like GUI.

I think the Mozilla Application Object Model (AOM) is
very elegant. Mozilla views the application GUI as a
tree. Manipulating that tree manipulates the GUI.

I think XML is abused by falling into the "Golden
Hammer" antipattern which says if all you have is a
hammer everything looks like a nail. Look at apache
jelly for example. Executable XML is a bad idea.

However, Mozilla's use of XML to represent a GUI is a
good idea. Since XML can be represented as a tree
structure, it is great for representing a GUI because
the relationships between the components in a GUI can
be represented well with a tree. Since DOM is a
standard way of representing and manipulating the XML
tree, it provides a uniform and simple way to
manipulate a GUI. Since the GUI can be respresented as
a DOM XML tree, programmers can use XPath to navigate
the GUI. Mozilla doesn't have support for XPath yet,
but Sulu does.

In writing swing GUI, often times I would have a
component within containers within containers within
containers so its easier to layout but navigating the
object model to get to that component can be a real
pain. This can now be done easily and elegantly with
XPath.

Q: How did you get started on Sulu?

Son To: Around 2001, I prototyped a POS (Point Of
Sale) system using Mozilla XUL. The Mozilla XUL gui
connected to the backend using jabber instant
messaging. Writing socket code in C++/javascript to
connect to jabber server was a real pain. Then I
discovered PyXPCOM which allowed me to write the same
code faster and more elegantly in python. However
PyXPCOM would break with a new Mozilla release and
getting it to work is a black art.

The Mozilla blackwood project promised Java support on
par with JavaScript, but that never happened and the
project seem to have died.

I wanted Mozilla XUL, but I did not want to write
business logic code in C++ or JavaScript. So in
septermber 2003, I decided to write an Mozilla XUL
rendering engine that will allow writing business
logic in java and python.

Q: Can you tell us some challenges you faced building
Sulu using Java and Swing?

Son To: The implementation strategy I choose was to
create org.jdom.Element Adapter (aka Wrapper) for
Swing components. Look at
net.openbx.sulu.swing.XulSwingAdapter.

The idea behind this use of the Adapter pattern is
that a client manipulates a Swing component using the
org.jdom.Element API. Manipulating an org.jdom.Element
will result in manipulation of the corresponding Swing
component. This technique worked well when there's a
one to one mapping between Mozilla XUL tags and Swing
components for example <button> and JButton.

Not all xul tags map one to one to Swing components,
for example <splitter> and JSplitPane. Mozilla treats
the <splitter> as a component just like <button> but
JSplitPane is not just a component, it's also a
container.

Q: Can you tell us how you handle the mapping from XML
tags/attributes to Swing classses/properties? Do you
use reflection? Do you use hand-coded glue code?

Son To: The mapping from xul tags to XulSwingAdapter
classes is hardcoded in
net.openbx.sulu.swing.XulSwingAdapterFactory although
the mapping should be refactored into a property file.

Q: Can you tell us what Sulu can do today? What works
and what needs to be done?

Son To: You can write fairly complex GUI, but since
there isn't a one to one mapping from Mozilla XUL to
Swing components, not all tags are compatible with
Mozilla... for example <table> ... Mozilla XUL doesn't
have a <table> tag. To make it compatible with
Mozilla, instead of delegating to swing components,
sulu will have to render its own components using
Java2D for example.

The goal is 100% Mozilla xul compatibility, but Sulu
isn't there yet. There's lot to be done like RDF.


Thanks Son To. Check back next week for the second
part of the XUL Titan interview with Son To discussing
why Son chose Python for scripting, what's the state
of CSS support, how Sulu differs from alternative XUL
toolkits for Java, what the future holds for Sulu and
much much more.   

Full interview and links @
http://xul.sourceforge.net/post/2004/06/xul_titan_interview_son_to_of_sulu_fame_part_i.html

  - Gerald

-------------------
Gerald Bauer

Mozilla XUL Developers Group |
http://groups.yahoo.com/group/mozilla-xul
PHP XUL Developers Group     |
http://groups.yahoo.com/group/php-xul
Perl XUL Developers Group    | http://groups.yahoo.com/group/perl-xul


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