On Tue, 4 Feb 2020 at 15:40, Volker Hilsheimer <volker.hilshei...@qt.io> wrote: > >> This works, but now you are encoding the visual hierarchy of the widgets > >> in two places: when asking the presumed parent to create the widgets; and > >> when setting up the layout, which might do things differently (esp once > >> you start refactoring complex UIs).# > > > > That's not a problem. The code simply behaves as if you would have used the > > current constructors that take a parent parameter. > > > > Ownership transfers between different qt parents don't violate the > > invariant. And they continue to work just like before. > > > So how is the above usage of makeChild an improvement over calling operator > new to instantiate your objects?
The result of makeChild never leaks. > > But that just means that QBoxLayout::addWidget(std::unique_ptr<>) has to > > behave imho saner in that edge case and actually delete the widgets that > > were added but never parented. (And I should really implement that to show > > how it would work.) > > > That seems like a terrible idea. One of the layout’s jobs is to set up the > parent/child hierarchy so that you as a developer don’t have to. I don't see how that idea changes that. > Do we really want to make it harder for people to write UIs just because the > resulting code doesn’t satisfy a C++ idiom? It's not a question of satisfying idioms for the sake of satisfying idioms, it's a question of avoiding bugs that we know based on decades of experience to be difficult to avoid with raw pointers. > If you don’t care about the things that QObject/QWidget does for you, then > don’t use QObject/QWidget. And if you do use QObject/QWidget and get a > consistent object model from it, then I’m really not convinced that adding > smart pointers to the API is making the code clearer, or in any way more > explicit. It’s not like the ability of using std::unique_ptr means that > people no longer have to be familiar with Qt’s basic concepts to use it > correctly. Correct, but if code moves a std::unique_ptr into a function call argument, I know that ownership is transferred, by just glancing at the code. With a raw pointer, I don't know that. _______________________________________________ Development mailing list Development@qt-project.org https://lists.qt-project.org/listinfo/development
