[Development] QTCS2019 Notes from QtQml session

Eike Ziller Eike.Ziller at qt.io
Mon Nov 25 10:25:00 CET 2019

> On 22. Nov 2019, at 11:52, Kai Uwe Broulik <kde at privat.broulik.de> wrote:
> Hi,
> > these are the notes on the QtQml session:
> > Versioning
> > ----------
> >
> > Once we get rid of unqualified lookups we don't need any QML versioning
> > anymore. At least the minor version will become optional already in 5.15
> > for well-behaved QML documents. In QML 3 it won't be allowed.
> While I agree with this overall, there's still one caveat which I haven't seen discussed yet:
> Imagine I have the following code:
> Item {
>    id: foo
>    property color prettyColor: "#f0f"
>    Rectangle {
>        color: foo.prettyColor
>    }
> }
> Right now "foo" refers to the Item. What if in a future update, Rectangle gains a new property "foo". Unless you want to force everyone to be explicit by using "this" (e.g. width: this.height) everywhere, which would be annoying, I don't see how this can be made future-proof without some form of versioning or some other magic solution?

Similar things can happen in C++ with method names.
C++ got the ‘override’ keyword to make these breakages detectable by tooling.
It looks to me like the case id==propertyname would also be detectable by tooling?

Br, Eike

Eike Ziller
Principal Software Engineer

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