[Development] The future of smart pointers in Qt API

[Shawn Rutledge]

On 1 Feb 2020, at 19:20, Daniel Teske <qt at squorn.de<mailto:qt at squorn.de>> wrote:

Now to take your next example: setParent is not fine. setParent can be used in 4 different ways:

child->setParent(child->parent()): Invariant holds
child->setParent(newParent): Invariant holds
child->setParent(nullptr): Nope
orphan->setParent(parent): Nope

The solution is I have is to replace setParent with two functions: adoptChild + releaseChild, which both ensure that the invariant always holds.

And to deprecate setParent. ...

In Qt Quick we plan to have a unified ownership tree in Qt 6: visual parent item will be the same as QObject parent.  (Whereas in Qt 5, QQuickItem::setParentItem() sets a different pointer.)  And Item.parent is a property, so it’s expected to be able to reparent a subtree of Items by setting its parent to a different one.  How do you think that should be handled?

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