[Interest] Force property's binding to be executed from C++

[Xavier Bigand]

That the problem, I can easily call my SkinManager::updateSkin when
the skin changed, because it's a cpp attribut too (the selected skin).
But I have to call it when the QmlEngine have reevaluated the
properties values not before.

Getting property values directly from cpp code doesn't execute
bindings (as much as I know), so I am trying to call this slot
(SkinManager::updateSkin) from Qml where it should be easier to fix
this calling order issue.


If I create a property that depends of all others it be reevaluated
after the others, then I will be able to invoke my cpp slot from his
onChanged signal.

The difficulty is to create this property.




My QML component looks like to this :


HomeDesignSkins.qml :


Item {

    id: homeDesignSkins

       readonly property color accentucationColor: {
                                                    // In cpp
SkinManager::updateSkin() method can be invoked before the execution
of this binding,

        if (application.product === Product.ProductOutdoor)
                                                // the better way to
solve this issue is to create a binding dependency

            return "#45a785"

        else if (application.product === Product.ProductMyDreamHome)

        {

            if (settings.skin === "MyDreamHomeThemeCanson")

                return Qt.rgba(235 / 255, 130 / 255, 122 / 255, 255 / 255)

            else if (settings.skin === "MyDreamHomeThemeMilli")

                return Qt.rgba(242 / 255, 118 / 255, 82 / 255, 255 / 255)

            else

                return Qt.rgba(145 / 255, 135 / 255, 148 / 255, 255 / 255)

        }

        else

            return "#8da7c0"

    }


    ...


    // Here we have numerous properties used to describe our GUI skin
(some are shared with the cpp code for our 3D rendering)


    Object {

        property string homeDesignSkinsProperties: {

                   var propertyValues

                   for (var propertyName in homeDesignSkins)

                          propertyValues += propertyName + " "
                        // How retrieving the property values by their
names

                   return propertyValues

             }


            onHomeDesignSkinsPropertiesChanged: {
               // This signal should be called once after that all
properties of homeDesignSkins where reevaluted when the skin changed

                   skinManager.updateSkin()
                         // skinManager is the instance of the cpp
SkinManager singleton, updateSkin is an Q_INVOKABLE method

            }

    }

}






2016-08-23 21:29 GMT+02:00 Jason H <jhihn at gmx.com>:

> If I understand you correctly, and I probably don't, the skin component
>
> Skin {
> signal skinPropertyChanged();
> property color accentucationColor: "red"
> onAccentucationColorChanged: skinPropertyChanged()
> }
>
> SkinManager {// exposed C++ class
>     id:skinManager
>     property var currentSkin: null;
>     onCurrrentSkinChanged: updateSkin(); // handle when the skin switches
> }
>    Connections {
>       target: currentSkin
>       onSkinPropertyChanged: id:skinManager.updateSkin() // handle when
> propterties of the skin change.
>    }
>
> Will that work?
>
>
> *Sent:* Tuesday, August 23, 2016 at 1:12 PM
> *From:* "Xavier Bigand" <flamaros.xavier at gmail.com>
> *To:* interest at qt-project.org
> *Subject:* [Interest] Force property's binding to be executed from C++
> Hi,
>
> To skin our GUI we have a dedicated qml component instanced once that
> contains all necessary values under properties.
> I am able to access to those properties from C++ code but they aren't
> correctly synchronized with the selected skin.
>
> Here is my cpp code :
>
>
>     void SkinManagerWrapper::updateSkin() const
>
>     {
>
>         QObject*    skinItem = mRootObject->findChild<QObject*>("hdGUI", Qt::FindDirectChildrenOnly);
>
>
>
>         core::SkinManager*  skinManager = core::SkinManager::singleton();
>
>
>
>         // General
>
>         skinManager->accentuationColor = convert(skinItem->property("accentuationColor").value<QColor>());           // skinManager->accentuationColor is actually a cpp property ;-)
>
>     }
>
>
> The property method return the previous value before the execution of the
> binding, because in the qml binding the value is depending of the selected
> skin.
>
> As workaround I am trying to create a qml property that depend of all
> properties of our skin component ("HomeDesignSkins"), but If it is possible
> to retrieve dynamically properties names of the component, I can't figure
> out retrieving values of properties by string names.
> The Idea is to be able to use the onChanged signal of this property to
> invoke my cpp updateSkin method, this should resolve dependency order issue.
>
> Maybe their is an other way to do it, else I am searching to way to
> retrieve property values in qml from their names.
>
>
> --
> Xavier
> _______________________________________________ Interest mailing list
> Interest at qt-project.org http://lists.qt-project.org/
> mailman/listinfo/interest
>



-- 
Xavier
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