Thanks for doing this.
Here is what i suggest to make the change less intrusive:
For the constructors themself in every classes.
// Removed the '=nullptr' default parent, and added QT_UNSAFE_API
QT_UNSAFE_API explicit QLineEdit(QWidget *parent);
QT_UNSAFE_API explicit QLineEdit(const QString &, QWidget *parent);
// Added new non-deprecated constructor not taking parent.
explicit QLineEdit(const QString & = {});
//The QObject::makeChild method:
template <class T, class... Args> T* QObject::makeChild(Args&&... args)
{
auto n = new T(std::forward<Args>(args)...);
n->setParent(this);
return n;
}
That way, std::make_unique still work, and constructing objects on the
stack does not change.
For the cases where the parent in the constructor has another meaning,
we would need another factory function (makeChild) in the relevant
class. Or interept the ParentChanged, or reimplement setParent in that
class.
What do you think?
Consider this "old" code:
QWidget widget;
QVBoxLayout *topLayout = new QVBoxLayout(&widget);
QVBoxLayout *childLayout = new QVBoxLayout();
topLayout->addLayout(childLayout);
That would, if I understood you correctly, translate too:
QWidget widget;
QVboxLayout *topLayout = widget.makeChild<QVBoxLayout>();
auto childLayout = std::make_unique<QVBoxLayout>();
topLayout-addLayout(std::move(childLayout));
Both topLayout and childLayout do end up with the same parent. In the
old code, the QLayout ctor which takes a parent widget, calls
QWidget::setLayout.
Thus I think overriding setParent or interpreting ParentChanged would
not work.
Though makeChild could work, that is we would need:
template <class T, class... Args> T* QWidget::makeChild(Args&&... args)
{
auto n = new T(std::forward<Args>(args)...);
n->setParent(this);
if constexpr(std::is_base_of<QLayout, T>)
setLayout(n);
return n;
}
I guess whether that is feasible depends on many ctors assign additional
semantics to the parent parameter.
daniel
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