ubuntu-phone team mailing list archive

["Vladimir M." <mlvl.jr@xxxxxxxxx>]

Sure, you can always wire as many objects as possible to smth existing in a
scene or set as a context property -- it's a simple Q_PROPERTY assignment
on the C++ side, with a pointer passed to the setter (and works as soon as
you declare the property on the QML side (or register and instantiate a C++
implemented item)).

After all, these are ordinary QObejcts passing pointers (to each other) to
each other :)
(plus some memory management -- automatic on the QML side, and QObject
parent-tree based on the C++ side)

Vladimir


On Mon, Sep 30, 2013 at 6:24 PM, Николай Шатохин <n.shatokhin@xxxxxxxxx>wrote:

> What if I will create property backend in QML type and then I will set
> this property in all QML objects to global object? So, theoretically this
> can solve my problem.
>
>
> 2013/9/30 Vladimir M. <mlvl.jr@xxxxxxxxx>
>
> Then, it looks like the standard way would be to have an instance of the
>> item embedded in each page in the stack.
>>
>> If this turns out to be too resource consuming, you may try to play some
>> tricks like removing it from all the pages and overlaying over the whole
>> stack (if the item will always be in the same place, and have the same
>> geometry, this will be rather simple, children order or z-value will allow
>> it place it on top).
>>
>> If geometry is different for each page, this may get trickier (ultimate
>> solution may be some sort of a "placeholder item" having the right place in
>> each page, to which the item gets parented when the placeholder becomes
>> visible, with "fill" anchoring).
>>
>> On the other hand, if the item has to have it's state consistent between
>> the pages, then even if its is feasible performance-wise to embed it into
>> all of them, some sort of common "view state model" should probably exist,
>> and this again suggests just using a single instance...
>>
>> Vladimir
>>
>>
>> On Mon, Sep 30, 2013 at 3:07 PM, Николай Шатохин <n.shatokhin@xxxxxxxxx>wrote:
>>
>>> I need to have this object in different qml files (for i.e. GameChat
>>> must be shown on GameCreation,Game,GameResults pages: this it differents
>>> QML files and differents pages in PageStack), but I created only one
>>> QtQuickView in main.cpp. So, do view is qml file or QtQuckView object?
>>>
>>>
>>> 2013/9/30 Vladimir M. <mlvl.jr@xxxxxxxxx>
>>>
>>> You probably can't share a single instance of a QML visual item between
>>>> views, but as soon as you have the type registered properly / importable /
>>>> etc, you can use instantiate it in as many views as you like.
>>>> A QObject pointer can be passed around to items living in different
>>>> veiws inside the same application, of course (but watch out for memory
>>>> management issues -- see CppOwnership / QMLOwnership  / etc in the docs
>>>> under "memory management").
>>>>
>>>> Easiest way may be to set the same object as a context prop for several
>>>> views (unless you have some objections to this practice, like ones
>>>> mentioned up in the thread).
>>>>
>>>> Lastly, there is that (legitimate) trick allowing QML items to be
>>>> "rendered" by other items, resulting in the same item being shown in
>>>> multiple places of the same scene (but being manipalatable anywhere except
>>>> its actual position) -- look into the shader effects and such.
>>>>
>>>>
>>>> On Mon, Sep 30, 2013 at 2:34 PM, Николай Шатохин <n.shatokhin@xxxxxxxxx
>>>> > wrote:
>>>>
>>>>> What if I need to show the same QML object in two different places?
>>>>> How to do this? How to create new QML object without recreating it in C++?
>>>>>
>>>>>
>>>>> 2013/9/30 Николай Шатохин <n.shatokhin@xxxxxxxxx>
>>>>>
>>>>>> 0_o. I didn't know that all objects in QML are global. Thank you very
>>>>>> much.
>>>>>>
>>>>>>
>>>>>> 2013/9/30 <mrqtros@xxxxxxxxx>
>>>>>>
>>>>>>  Omg declare global engine object in main qml file and that's all
>>>>>>>
>>>>>>> 30.09.13 13:19 Николай Шатохин написал(а):
>>>>>>> I'm using qmlRegisterType now. I have problems, because two QML
>>>>>>> objects in different QML files it is two different objects in C++. I
>>>>>>> registered as type class that have static object of Engine, but now I have
>>>>>>> butthurt with it (I need retranslate all signals, getters and setters)
>>>>>>>
>>>>>>>
>>>>>>> 2013/9/30 Michael Zanetti <michael.zanetti@xxxxxxxxxxxxx>
>>>>>>>
>>>>>>>> On Monday 30 September 2013 12:05:03 Николай Шатохин wrote:
>>>>>>>> > Can I set only one object as context property that contains other
>>>>>>>> objects
>>>>>>>> > (and this objects contain objects too) and get this deep objects
>>>>>>>> in QML?
>>>>>>>> >
>>>>>>>> > For i.e. I have object of class Engine that has object of class
>>>>>>>> Game, Game
>>>>>>>> > contains object of Ship and Ship contains object of Reactor. So,
>>>>>>>> I set
>>>>>>>> > object of Engine as context property and in QML write:
>>>>>>>> >
>>>>>>>> > engine.game.ship.reactor
>>>>>>>> >
>>>>>>>> > Can I use it?
>>>>>>>>
>>>>>>>>
>>>>>>>> Yes, given that "game" is a Q_PROPERTY() of "enigne", "ship" is a
>>>>>>>> Q_PROPERTY()
>>>>>>>> of "game" etc...
>>>>>>>>
>>>>>>>> Still, I recommend to register the type of the Engine instead of
>>>>>>>> setting it as
>>>>>>>> a context property.
>>>>>>>>
>>>>>>>> It's really just using qmlRegisterType() instead of
>>>>>>>> setContextProperty(). It's
>>>>>>>> not more or more complex code, but gives you better ways of
>>>>>>>> structuring your
>>>>>>>> QML code.
>>>>>>>>
>>>>>>>> >
>>>>>>>> >
>>>>>>>> > 2013/9/30 Николай Шатохин <n.shatokhin@xxxxxxxxx>
>>>>>>>> >
>>>>>>>> > > I've already found this solution:
>>>>>>>> > >
>>>>>>>> http://qt-project.org/doc/qt-5.0/qtqml/qtqml-cppintegration-contextpropert
>>>>>>>> > > ies.html It helps. Thanks.
>>>>>>>> > >
>>>>>>>> > >
>>>>>>>> > > 2013/9/30 Michael Zanetti <michael.zanetti@xxxxxxxxxxxxx>
>>>>>>>> > >
>>>>>>>> > >> On Sunday 29 September 2013 13:45:01 Vladimir M. wrote:
>>>>>>>> > >> > Sounds like a "context property" use case (you plain set a
>>>>>>>> QObject as a
>>>>>>>> > >> > context property for a view's root scope, w/o even
>>>>>>>> registering the
>>>>>>>> > >>
>>>>>>>> > >> object's
>>>>>>>> > >>
>>>>>>>> > >> > type, and all its properties and invokables become
>>>>>>>> available).
>>>>>>>> > >>
>>>>>>>> > >> I don't recommend using context properties. While they are
>>>>>>>> useful for
>>>>>>>> > >> some
>>>>>>>> > >> cases, this one doesn't seem to be one of those. Using too
>>>>>>>> many global
>>>>>>>> > >> context
>>>>>>>> > >> properties can make the code very ugly to work with.
>>>>>>>> > >>
>>>>>>>> > >> You probably want to create something like this:
>>>>>>>> > >>
>>>>>>>> > >> class ViewController: public QObject
>>>>>>>> > >> {
>>>>>>>> > >>
>>>>>>>> > >>   Q_PROPERTY(QList<MyClass> viewObjects READ viewObjects NOTIFY
>>>>>>>> > >>
>>>>>>>> > >> viewObjectsChanged)
>>>>>>>> > >> ...
>>>>>>>> > >> QList<MyClass> viewObjects() const {
>>>>>>>> > >>
>>>>>>>> > >>   return objectList;
>>>>>>>> > >>
>>>>>>>> > >> }
>>>>>>>> > >> ...
>>>>>>>> > >> };
>>>>>>>> > >>
>>>>>>>> > >> qmlRegisterType<ViewController>(uri, 0, 1, "ViewController");
>>>>>>>> > >>
>>>>>>>> > >> Then in QML you can do something like this:
>>>>>>>> > >>
>>>>>>>> > >> ViewController {
>>>>>>>> > >>
>>>>>>>> > >>   id: viewController
>>>>>>>> > >>
>>>>>>>> > >> }
>>>>>>>> > >>
>>>>>>>> > >> Repeater {
>>>>>>>> > >>
>>>>>>>> > >>   model: viewController.viewObjects
>>>>>>>> > >>   MyView {
>>>>>>>> > >>
>>>>>>>> > >>     property var viewObject: viewController.viewObjects[index]
>>>>>>>> > >>
>>>>>>>> > >>   }
>>>>>>>> > >>
>>>>>>>> > >> }
>>>>>>>> > >>
>>>>>>>> > >>
>>>>>>>> > >> Note that if you want your code to adjust more flexible (i.e.
>>>>>>>> the
>>>>>>>> > >> viewObjects
>>>>>>>> > >> change a lot), consider using a QAbstractListModel (or some
>>>>>>>> other model)
>>>>>>>> > >> instead of a QList.
>>>>>>>> > >>
>>>>>>>> > >> Hope this helps,
>>>>>>>> > >> Michael
>>>>>>>> > >>
>>>>>>>> > >> > On Sun, Sep 29, 2013 at 6:38 AM, Николай Шатохин
>>>>>>>> > >>
>>>>>>>> > >> <n.shatokhin@xxxxxxxxx>wrote:
>>>>>>>> > >> > > Hello.
>>>>>>>> > >> > >
>>>>>>>> > >> > > When I create a class in C++, I can register it for QML
>>>>>>>> and can
>>>>>>>> > >> > > create
>>>>>>>> > >> > > view for it. It's very convenient. But, if I need many
>>>>>>>> objects of the
>>>>>>>> > >>
>>>>>>>> > >> same
>>>>>>>> > >>
>>>>>>>> > >> > > type, and need to show few views on screen, I got problems.
>>>>>>>> > >> > > Is it possible to register QML type for object, not for
>>>>>>>> class?
>>>>>>>> > >> > > If I change some object, I need to see only its view
>>>>>>>> changed.
>>>>>>>> > >> > >
>>>>>>>> > >> > > Best regard,
>>>>>>>> > >> > > Nick
>>>>>>>> > >> > >
>>>>>>>> > >> > > --
>>>>>>>> > >> > > Mailing list: https://launchpad.net/~ubuntu-phone
>>>>>>>> > >> > > Post to     : ubuntu-phone@xxxxxxxxxxxxxxxxxxx
>>>>>>>> > >> > > Unsubscribe : https://launchpad.net/~ubuntu-phone
>>>>>>>> > >> > > More help   : https://help.launchpad.net/ListHelp
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>> --
>>>>> Mailing list: https://launchpad.net/~ubuntu-phone
>>>>> Post to     : ubuntu-phone@xxxxxxxxxxxxxxxxxxx
>>>>> Unsubscribe : https://launchpad.net/~ubuntu-phone
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>>>>>
>>>>>
>>>>
>>>
>>
>