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Re: [e4-dev] how to contribute to toolkit model ?
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Yves,
I think most of us agree on the advantages of declarative UI (or
explicit representation of a GUI using a DOM), but some of us disagree
that the solution is an XML-based representation. XML might be a good
common representation in some contexts, but I think that in Eclipse EMF
is a much better candidate.
I've worked a lot with XML-based UI representations and have looked at
most of the languages that exist, and I've contributed scripting and
editing tools to XSWT. XSWT is almost equivalent to XWT, by providing a
direct mapping to SWT (no abstraction). The general problems of XSWT
were twofold:
1) By being a direct mapping to SWT, it didn't really make things
simpler, as you both had to understand SWT and the mapping technique
(which became complex to support all aspects of SWT).
2) Working with XML is perhaps OK if you're editing it as a file, but
when you must manipulate the XML DOM in an application, e.g. for
changing the UI during runtime or building the XML document from some
other representation, it becomes cumbersome. This is partly because of
XML's weak, untyped structure, partly because of the complexity of the
mapping to SWT, which to some extent is reflected in the application's code.
So the problem was not that there is no standard for XML-based
declarative UI, but intrinsic problems with XML and the mapping to SWT.
For me the solution was to reuse the good ideas from XSWT in an
EMF-based solution. I was about to take Wazaabi
(http://www.wazaabi.org/index.php?title=Main_Page) as the starting
point, but since I wanted to better understand the implementation issues
and instead started on TM.
A weakness of a model-based solution seems to be that you have to model
all the widgets you want to use in advance, while in X(S)WT you can just
use the name of the widget class as a tag and you get what you want.
However, it's easy to use the same reflection techniques as XWT uses, to
generate the EMF-based model, since EMF supports dynamically creating
classes and instances.
As I've argued before, an important strength of an EMF-based
representation is how well UI model instances can be managed by existing
(and future) Eclipse tools. (EMF is almost becoming a native Eclipse
object model, now.)
Hallvard
yves.yang@xxxxxxxxxxx wrote:
A declarative UI is very important for e4 to simple UI development for
enterprise SI presentation. It provides a separation between concept and
implementation, and unify all UI frameworks and data frameworks (including
EMF) to work together. It should be the foundation of eclipse for all UI
Tools such as VE, MDA like PMF/EGF. So the standardization of declarative
UI in e4 is absolutly necessary for the success of e4.
Without this standard, it will be a masse. We are already in this
situation in Java. There are XUL, Xform, XSWT and others, but no standard.
Who dare to use it? Which tool support it?
Best regards
Yves YANG
EMF seem higher level technology than XML. EMF provide many advanced tools
to solve the actual world's problem. A XML file is a data aggregation.
But,
it is simple to understand. However parsing many XMLs or one big XML is
not
lightweight absolutely. And so I don't much like the idea of "XML
Everywhere". But, One question is that, is it possible to make all
additional technologies as the options for e4? we don't need be forced to
choose one specific technology?
best regards,
Jin Mingjian
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