Custom type with typedef's in QML

St.Stanislav

Hello all! I have the issue connected with the custom types in QML. I have tried a lot of different approaches, so my actual code is little messy now to be posted here as "what I have done" thing. What is the correct way to use/register/declare (qRegisterMetaType, Q_DECLARE_METATYPE) custom type in QML in the following situation. I have some custom typedefs like:

typedef quint8 ADCValue;
typedef quint32 ValuePosition;

Then I have structure with this variables:

struct Example {
    Q_GADGET
    Q_PROPERTY(PhotodiodePosition position MEMBER m_position)
    Q_PROPERTY(PhotodiodeADC whiteLevel MEMBER m_whiteLevel)
public:
    ADCValue adc = 0;
    ValuePosition value = 0;
}

I want to use aforementioned structure in the QML to edit and pass back to C++. I use QAbstractListModel with the class, which has struct Example as a member. So my model is working well, all parameters are being passed well through data/setData mechanism. One of the roles is connected with the Example.

In my QML delegate file I have created appropriate property:

property var currentExample: model.exampleRole

In the model I have return Example's copy:

...
    case ExampleRole: {
        return QVariant::fromValue(item->example());
    }
...

And since this place everything works unexpected (with different combinations of registerging/declaring ADCValue, ValuePosition and Example): sometimes I cannot show in console my struct (output just stops to display something after typedefs values), sometimes I cannot modify this object in QML:

currentExample.adc = 10
console.log(currentExample) // here it's still 0

and so on...

So my question can be a slightly wide, but: What is the correct way to work with typedefs, gadgets in QML correctly?

St.Stanislav

I have found partial "solution":

QML can not correctly work with quint8 when it was typedefed and qRegistered. Changing initial type to quint32 solved the issue when QML can not correctly display its value.
Passing Q_GADGET to QML via model's method data with using QVariant as a "transport" type works incorrectly (Q_GADGET inner variables cannot be changed for some reason), but passing it directly with separate model's method as

Example getExpample(int index);

works well. Anyway copying the Example's object in the both cases works well, but the last one allows to modify Example's members in QML.

I can not say that my issue was solved (now I'm going to use quint32 and the second approach to pass Q_GADGET copy to QML), but I'm wondering, if this is a correct QML/QVariant/Q_GADGET behaviour to avoid such issues further.