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From: David Turner (dkturner_at_[hidden])
Date: 2004-03-04 10:37:54


Jesse Booher wrote:
>>>> dave_at_[hidden] 03/04/04 08:59AM >>>
>> button("click me") doesn't have to be a widget. Think expression
>> templates. It can just build up a type to be used by window to add a
>> button.
> Well said. This exemplifies the reason why most gui toolkits are so
> horrible to use, they allow implementation technicalities to dictate
> interface. Having to decide where an object is going to live before any
> of its properties can be set is a clear violation of object oriented
> design principles but we live with these kind of problems all the time for
> supposed technical reasons.

Okay, you make a good point. On the other hand, I think that requiring
child elements to have an explicit owner is good design; the problem is
that the constructor syntax for widgets doesn't make it clear that they
are in fact being constructed by the owning window. If the syntax were:

window w("Test");
button b = w.spawn("button");
b.label("Click me");

then the situation would be much clearer.

At a broader level, I'd argue that there is a good reason to use this
document/elements design because the type of the widgets have to match the
type of window they're going to go into. Does that sound strange?
Consider a linux implementation that allowed a run-time choice between a
Qt and a GTK interface - or even both at the same time. It would clearly
be an error to put a Qt widget into a GTK window. The document/elements
model prevents this type of abuse.

But as I said yesterday, I'm not religious :-). If my opinion is in the
minority, I'll happily adapt the interface.

David Turner

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