[PyQt] PyQt support for Qt 4.7

[Giovanni Bajo]

On Thu, 07 Oct 2010 16:34:41 +0100, Phil Thompson
<phil at riverbankcomputing.com> wrote:
> On Thu, 7 Oct 2010 00:35:16 +0200, David Boddie <david at boddie.org.uk>
> wrote:
>> On Tue Oct 5 09:36:49 BST 2010, Phil Thompson wrote:
>> 
>>> The minehunt example only seems to need support for lists of QObjects.
>>> Are
>>> there any other examples anywhere that have different use cases?
>> 
>> I guess that's more or less what it is, though it needs something extra
> to
>> make the QML engine aware of the new TileData type, used as a property
> type
>> in the MinehuntGame class, and used as the model that holds the tile
> data
>> in
>> the game. If you can figure out a way to expose homogeneous Python
lists
> as
>> QDeclarativeListProperty containers then that would be cool.
> 
> Done that.
> 
>> Looking through the examples, there are places where qmlRegisterType is
>> used
>> to add C++ classes to QML as new item types. The "Writing QML
extensions
>> with
>> C++" tutorial in examples/declarative/tutorials/extending is one of
> these.
> 
> ...and there we hit the showstopper.
> 
> It looks like it is not possible to publish Python types to QML (and use
> the QML import statement) because QML uses a QObject's staticMetaObject
> instead of calling metaObject(). That automatically limits it to types
> known at compile time and no way to inject dynamic meta-objects created
at
> run time.

I think that's because they need to construct new instances for that type
at runtime. I can't see how an object could be instantiated through a
pointer to its QMetaObject instance (let alone a *dynamic* meta object).
You would probably need to add a different qmlRegisterType() overload that
gets a QMetaObject* and a pointer to a factory function that instantiates
objects of that type.

Until you agree with Nokia on a design for this, as a temporary
workaround, you could generate a fixed pool (eg: N=16) of static objects
that can be registered in place of the dynamic object; basically, when the
pyqt user calls qmlRegisterType(), you fetch the next static object, make
it a "delegator" for the user's dynamic object, and register that to qml. I
think it might be sufficient to duplicate the metaobject information and
then forward a few functions like invoke().

It's ugly, but at least it's all internal to PyQt and you can expose the
correct API to Python users. When you get this fixed with Nokia, you can
skip all this. 
-- 
Giovanni Bajo   ::  rasky at develer.com
Develer S.r.l.  ::  http://www.develer.com

My Blog: http://giovanni.bajo.it