[Development] Qt6 source changes

Sascha Cunz sascha at cunz-rad.co.uk
Thu Nov 1 11:58:17 CET 2018

On 2018-10-31 16:46, Thiago Macieira wrote:
> Qt6 won't be fully source-compatible. The idea is that we'll break it 
> to fix
> things, but attempt to keep compatible as much as possible to avoid 
> death by a
> thousand paper cuts.

Does this rule out some kind of smart pointer that would be used to hold 

I've seen lots of commercial code bases in the past where QObject 
inheriting classes are combined with QExplicitlySharedDataPointer - 
while at the same time relying on having a parent in those QObjects.

- There's some class for which QObject benefits like Signals/Slots are 

- They are strongly owned by some other QObject based entity

- A lot of code stores a reference to them (In terms of a QESDP), where 
   - the reference _should_ be invalidated during destruction
   - the existence of such reference (to a child) _should_ stop the 
parent from destroying that child.

- The overhead of QPointer is not desirable

I know these requirements are kind of a paradox. But both variants of 
this are a pattern, I find relatively often in customer's code bases.
I would really like to have an easy way to give such customers a "sane" 
way forward.


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