[Kde-bindings] A sample of our subset of QtC

[Adam Treat]

On Saturday 11 January 2003 08:17 am, Richard Dale wrote:
> On Saturday 11 January 2003 12:03 pm, Joseph Wenninger wrote:
> > For .Net/Mono/pnet you have to track both, the managed and the reall c++
> > object to be able to handle repartending of widgets (eg
> > QWidget::reparent) and derived classes correctly, without risking that
> > one of them gets deleted by the garbage collector, that's what Adam
> > tries to do with the managedObject void* pointer. It makes things easier
>
> I'm having trouble following the C# talk about garbage collection issues
> because the CLI has its own terms for things.
>
> Anyway, heres how the QtJava memory management works, and why I don't have
> a problem with re-parenting widgets:

What you've just described is exactly what we are doing with the Qt# bindings 
_right now_.  In fact we took the design pattern from QtJava (to be honest 
almost all of Qt# was taken from the example provided by QtJava and QtC, to 
which we are greatly indebted ;), but it is overly complicated and I think 
we've found a way to make it more elegant and less complicated in our next 
release.

Basically, in our next release the Qt# class and it's corresponding QtC glue 
class will hold references to each other.  The QtC glue class will be 
primarily responsible for the lifetime of the Qt# class .. ie, the QtC class 
will call the Qt# Dispose method in it's dtor.

Holding a reference to the Qt# class in the glue is also useful for how we 
plan to override virtual methods.  Basically, if we override a virtual method 
in C# the glue will have to call the C# method and pass the arguments (many 
of which will be QObjects) and we need a way to automatically wrap those 
without having to go through yet another proxy method that'll do the 
wrapping.  The solution: store a managed reference and let the C# marshalling 
magic do the work.  It results in a very elegant solution because in C# we 
can override operators including implicit/explicit conversion.

Another advantage is to get rid of the Hashtable and all the overhead that 
implies.

Cheers,

Adam