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List:       kde-devel
Subject:    Re: Communication between C++ and QML
From:       David Edmundson <david () davidedmundson ! co ! uk>
Date:       2011-06-06 14:29:26
Message-ID: BANLkTiksktd9Cm70QAA319aqOFy4e+mebw () mail ! gmail ! com
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On Fri, Jun 3, 2011 at 10:12 PM, Stefan Majewsky
<stefan.majewsky@googlemail.com> wrote:
> Hi,
>
> I've been looking into QML again for kdegames. Some background: I
> added a QDeclarativeImageProvider to feed images from libtagaro's
> ThemeProvider into QML, and that mostly works (with an emphasis on
> mostly; QTBUG-14900). Then I tried something more difficult: I wanted
> to port a game from QML, and chose KNetwalk because it has its
> algorithms split in an AbstractGrid class, which is subclassed for the
> QGraphicsView representation.
>
> Now as far as I understand the (IMHO surprisingly sparse)
> QtDeclarative module documentation, the main gateway for transferring
> information between C++ and QML is
> declarativeView->engine()->rootContext()->setContextObject(). QML
> retrieves data from the properties of this object and the subobjects
> which it references, and invokes via JavaScript functions in this
> object to propagate user input to the C++ layer.
>
> Is this correct? If so, I get a feeling that it would require a
> potentially epic amount of boilerplate to make my already
> interface-agnostic data available to QML. Can I do anything to make
> this task simpler?
>

That's not the only way to link C++ and QML. You can also make your
QObject creatable during the QML runtime. It /may/ be easier for your
purposes.

In your application that creates the QDeclarativeView run
(for example)

qmlRegisterType<KExtHighscore::Manager>("KDEGames", 0, 1, "HighScoreManager");

Then in your qml files

import KDEGames 0.1

HighScoreManager{
 id: manager;
 //whatever else.
}

It should be mostly be a case of adding a few Q_PROPERTY and
Q_INVOKABLE macros into your header files, and making sure things
which should be public slots are.

David


> Greetings
> Stefan
>
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