[Interest] [Qt6] Gadgets in QML

[Shawn Rutledge]

On 2022 Jan 6, at 10:35, Ulf Hermann <ulf.hermann at qt.io<mailto:ulf.hermann at qt.io>> wrote:

To be frank it's been an annoyance for me that gadgets can't be instantiated the same way the QObject can within the QML document/tree. Is there a good reason to disallow this or is it simply not implemented? Am I missing some odd use/corner case why it's not a good idea?

It's not implemented yet, and there are some questions surrounding the desired syntax.

We already have group properties. So, if you have a property font of some value type, you can already do this:



MyObject {

   font {

       pointSize: 14

       bold: true

   }

}



That is very similar in syntax to what you would do with a full value type construction. Therefore, the extra syntax required for full value type construction seems some
what redundant. I've chosen the familiar "font" value type as example but you can do the same with custom value types.

What is missing is value types as default properties and value types in lists and JavaScript objects. Yet, declaratively putting QML types in lists and objects is already a rather buggy affair with object types. This needs to be fixed first.

Then there is the issue that you cannot have named custom value types at all so far (you can have anonymous custom value types, though). All of the currently available named value types are hardcoded. That has to be fixed eventually.

Finally, we will probably run into some grammatical ambiguities when we allow lower-case names on the left side of "object" intializers.

It’s good to hear that there might be hope still.  I was assuming we won't because it’s a value type, can be stack-allocated, cannot be passed by pointer, and needs to be copied or moved every time, i.e. even after instantiating declaratively, you’d have to move or copy at least once to put it into a destination, whatever that is.

https://bugreports.qt.io/issues/?jql=text%20~%20%22gadget%20qml%22<https://bugreports.qt.io/issues/?jql=text%20~%20"gadget%20qml"> finds a bunch of related requests like QTBUG-54983<https://bugreports.qt.io/browse/QTBUG-54983> QTBUG-79330<https://bugreports.qt.io/browse/QTBUG-79330> QTBUG-56484<https://bugreports.qt.io/browse/QTBUG-56484> QTBUG-72223<https://bugreports.qt.io/browse/QTBUG-72223> QTBUG-73399<https://bugreports.qt.io/browse/QTBUG-73399>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.qt-project.org/pipermail/interest/attachments/20220106/40a76593/attachment.htm>