[Qt5-feedback] C++ api to use for UI in addition to QML

[Alan Alpert]

On Tue, 17 May 2011 06:58:51 ext Alan Ezust wrote:
> On Mon, May 16, 2011 at 5:57 AM, Andre Somers <andre at familiesomers.nl> 
wrote:
> > Op Ma, 16 mei, 2011 2:43 pm, schreef Thiago Macieira:
> >> On Monday, 16 de May de 2011 12:03:30 Serhiy wrote:
> >>> So my point is that since QT itself uses C++ why not to have C++ api
> >>> for new features as well.
> >> 
> >> Because we lock ourselves to that API, due to C++'s binary compatibility
> >> requirements.
> >> 
> >> We like to have a minimal API that addresses the use-cases. We'll be
> >> doing it
> >> once in QML. Doing it again in C++ is more work and also harder to
> >> change later.
> > 
> > Sure. But there needs to be some sort of sane way to interact with QML
> > elements from C++, if QML is to be the main UI paradigm of Qt. At the
> > very least, it would make sense to make it possible to get a pointer to
> > a QObject based on a QML id.
> 
>     in QML 1.x, you can set
> objectName: "someObjectName"
>    on any QML Item and then use
> QObject::findChild<QDeclarativeItem*>("someObjectName")
>    to find it.
> 
> But that assumes the QML Items derive from QObject. When we move over
> to sceneGraph in QML 2.0, will that still be true?
> 
> I don't know how to find something by id, but I'll be following this
> thread in case someone else does.

You can't find an item by id from C++, it's a detail internal to the QML 
engine. ObjectName will continue to work in Qt 5 though.

In fact, QML 2.0 should have a very similar C++ API to QML1.x (because we 
expose so little of it). You will be able to instantiate QML scenes with 
components, and use the meta object system for introspection. It would help if 
you provide more detail than 'interact with'. What's missing from the QML 1.x 
C++ support that you want (keeping Thiago's points in mind, as he is entirely 
correct) ?

Another thing to keep in mind is that you won't have to write Javascript to 
use QML. Qt Creator has a QML design view that you can use, and then 
everything gets hooked up like it used to be with .ui files. Except with 
greater customization and more animations. With Qt 5, you will be able to 
create UIs without 'writing' QML, just by using the tools.

-- 
Alan Alpert
Senior Engineer
Nokia, Qt Development Frameworks