Re: Easiest way to build Qt/Gtk interfaces for Ada programs

["Yannick Duchêne (Hibou57)" <yannick_duchene@yahoo.fr>]

Le Fri, 28 Dec 2012 16:32:09 +0100, Dmitry A. Kazakov  
<mailbox@dmitry-kazakov.de> a écrit:

> On Fri, 28 Dec 2012 06:51:01 -0800 (PST), alb348@gmail.com wrote:
>
>> I am a interested in creating GUI applications with Ada, using either Qt
>> or Gtk (it must be one of these two, because these are the only toolkits
>> that provide full BiDi support).
>
> One important thing, which implies the obvious consequences. There is no
> easy way of building GUI as well as no way of adding GUI to an existing
> application.
>
> Ignoring casual applications, it is unfortunately so, that whatever
> framework you use, and what the application is supposed to do  
> functionally,
> you have to build it around the GUI.

On the opposite, this is the least recommended way to do. One should  
create the UI around the application. The cleanest in my opinion, is to go  
for a Model View Presenter (MVP), preferably with a passive view. The  
presenter is the glue between the application and the view, and is also a  
model of the view's behaviour. The view, if passive, only receive display  
request, along with the data (which it does not fetch itself, to be  
independent from the application), and transmit events and user gestures  
to the presenter. This has some advantages, including easier separate  
design and easier testing (if the communication between the presenter and  
the view is correctly specified before).

The hard part is the presenter, but the UI may be an hard part too, if you  
have ergonomic requirements. The UI may be made of anything, and has its  
own and separate specification. The presenter is less independent, and is  
related to the application. You have to figure a way to setup a  
communication channel between all three parts: between the application and  
the presenter (both way), and between the UI and the presenter (both way  
too).

See: http://martinfowler.com/eaaDev/ModelViewPresenter.html
Note: according to Martin Fowler, the “Model View Presenter” designation  
may not be relevant, but that term is still widely used, so many people  
understand it. He himself designate it under the term of “Supervising  
Controller and Passive View” instead.

> There is no easy way of building GUI

That part still remains true, and is not just applicable to UI alone.


-- 
“Syntactic sugar causes cancer of the semi-colons.” [1]
“Structured Programming supports the law of the excluded muddle.” [1]
[1]: Epigrams on Programming — Alan J. — P. Yale University