[Development] std::optional for Q_PROPERTY

[Kai Uwe Broulik]

Hi everyone,

something that came up during this year’s KDE Akademy was that we 
believe Q_PROPERTY should be able to handle std::optional, such that you 
get a null QVariant out of it if it has no value. The main use case 
being interfacing “more modern C++” with QML in a type-safe way, rather 
than using QJSValue::Undefined for invalid results.

The question is also, where do we draw the line: I could see a use for 
having an std::variant property for when we have a known set of types we 
accept (e.g. std::variant<QString, QIcon>). Again something where we 
currently would do a QVariant with manual conversions and missing 
introspection.

Is that something that we would like to see? I was told that a QMetaType 
is “full” and version bump needs to happen first before it can be 
extended or something?

Cheers
Kai Uwe