将TextStyle从c ++传递到QML

Question

I am having problems setting the TextStyle of a Label when using a c++ method, it always causes the app to crash.

I have a c++ getStyle() method. I want to be able to call it like so (parameters removed to simplify code example):

Label {
    id: myLabel                        
    text: "test with style"
    textStyle.base: _App.getStyle();
}

The following does NOT work:

TextStyle ApplicationUI::getStyle() {
    TextStyle *blueStyle = new TextStyle(bb::cascades::SystemDefaults::TextStyles::smallText());
    blueStyle->setColor(Color::Blue);
    return *blueStyle;
}

Currently the only way I have been able to get it working is to pass the entire Label object into a method and set the style with c++. This however makes the QML code more verbose leading to this:

Label {
    id: myLabel                        
    text: "test with style"
    onCreationCompleted: {
        _App.setStyle(myLabel);
    }
}

C++ (Works)

void ApplicationUI::setStyle(AbstractTextControl* label) {
    TextStyle *blueStyle = new TextStyle(bb::cascades::SystemDefaults::TextStyles::smallText());
    blueStyle->setColor(Color::Blue);

    label->textStyle()->setBase(*blueStyle);
}

Is there any way to pass the TextStyle directly to the QML Label without having to pass the Label object into the method?

Answer 1

After reading the documentation on text styles I would suggest you try something like this:

Page {
    content: Container {
        attachedObjects: [
            TextStyleDefinition {
                id: myStyle
                base: _App.getStyle()
            }
        ]

        Label {
            text: "A label with some text."

            textStyle {
                base: myStyle.style
            }
        }
    } // end of Container
} // end of Page

Answer 2

I managed to solve the problem after some browsing of the various .h files and experimenting.

QML:

Label {
    id: myLabel                        
    text: "test with style"
    textStyle.base: _App.getStyle();
}

C++:

QVariant ApplicationUI::getStyle() {
    TextStyleDefinition *textStyle = new TextStyleDefinition();
    textStyle->setColor(Color::Blue);

    QVariant style = textStyle->property("style");
    return style;
}

The trick is that when setting a Label's Style.base property from c++ it requires a TextStyle object, however when you set it from QML it expects a QVariant. Using ->property("style") we can get the QVariant which QML expects.