[Development] QList for Qt 6

[Philippe]

> People tend to use QList as a deque because of the fast prepend/take first

Simply, QArrayList should not be deprecated.
It is also useful to store large objects that needs to be sorted.

Philippe

On Wed, 22 May 2019 18:25:18 +0200
???? ?????????? <abbapoh at gmail.com> wrote:

> 4. Use QVector to implement QList<Foo>, if sizeof(Foo) <= sizeof(quint64) and Foo is movable
> 
> 
> What about fast prepend in that case? People tend to use QList as a deque because of the fast prepend/take first
> 
> ???? ??????????
> 
> 22 ??? 2019 ?., ? 15:49, Lars Knoll <lars.knoll at qt.io> ???????(?):
> 
> 
> Let’s conclude the topic of QList. I do see the concern about silent source breakages. Here’s what we’ll (I’ll) do then for Qt 6:
>  
>  1. Rename QList to QArrayList and make QList an alias to QArrayList
>  2. Move QStringList and QByteArrayList over to inherit from QVector (that should be source compatible)
>  3. Rename QStringList to QStringVector (keep QStringList as a compatibility name), same for QBAList
>  4. Use QVector to implement QList<Foo>, if sizeof(Foo) <= sizeof(quint64) and Foo is movable. I’m intentionally not using sizeof(void *) here, as types with sizes between 4 and 8 bytes would not have stable references in cross platform code, so I do not believe lots of code would assume that (or it would have broken on 64 bit).
>  5. Add a compile time switch that allows mapping QList completely to QVector or to a compatibility mode where QLists of large/non movable types are mapped to QArrayList
>  6. For now we don’t yet want to explicitly change all our API that uses QList to use QVector (as that would make merging from dev a pain, let’s do that later this year). But to test that everything we have works with QVector, we’ll set the compile switch to default to mapping to QVector.
>  7. Make the implementation of QArrayList fully inline and deprecate the class.
>  
>  Let me know if there are any major concerns with this plan. It should give us a good compromise, where we can move all of Qt over to QVector and test things early, as well as providing a compatibility mode for our users (slower but won’t silently break).
>  
>  Cheers,
>  Lars
>  
>  On 21 May 2019, at 10:38, Giuseppe D'Angelo via Development <development at qt-project.org> wrote:
> 
> Il 21/05/19 10:30, Konstantin Shegunov ha scritto:
> That's a hard one. Especially since very few could keep in their brain a list of the sizes of each and every one class from Qt. It also differs depending on architecture.
> 
> I know. That's my point: we can't just break this level of source compatibility.
> 
> Thanks,
> 
> -- 
> Giuseppe D'Angelo | giuseppe.dangelo at kdab.com | Senior Software Engineer
> KDAB (France) S.A.S., a KDAB Group company
> Tel. France +33 (0)4 90 84 08 53, http://www.kdab.com
> KDAB - The Qt, C++ and OpenGL Experts
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