Why so many QStyles

[Hugo Pereira Da Costa]

On 10/04/2014 12:37 PM, Dominik Haumann wrote:
> On Friday 03 October 2014 00:09:11 Aleix Pol wrote:
>> On Thu, Oct 2, 2014 at 10:10 PM, Hugo Pereira Da Costa <hugo.pereira at free.fr
>>> wrote:
>>>
>>> hi all,
>>>
>>> I guess its a question to Qt experts or possibly low level KF5 experts.
>>>
>>> When comparing debugging outputs when running app + style against Qt4 and
>>> Qt5, I've noticed the following significant difference.
>>> In Qt4, as far as I can tell, QStyle was only instanciated one per QApp,
>>> and deleted at the end.
>>> In Qt5 this seems not to be true anymore and I've seen up to 6 QStyle
>>> running concurently for a single Kate Window, increasing to 13 when
>>> opening
>>> 'open file' dialog, decreasing back to 6 when closing it, etc.
>>> Is this a known feature ? Will this stay ?
>>>
>>> (I'm running a rather old checkout of Qt-5.4)
>>>
>>> If yes, there need to be some design change in Oxygen (as well as in
>>> breeze), to use singletons rather than QStyle's QObject's children for
>>> many
>>> things, with regard for instance caching, configuration, and even possibly
>>> even filters, otherwise I foresee quite some overhead ...
>>>
>>> Information welcome,
>>>
>>> Best regards,
>>>
>>> Hugo
>> Hi Hugo,
>> Thanks for looking into this! :)
>>
>> I would recommend to start by adding a breakpoint on the style's
>> constructor to see who is calling it. To me it sounds like a bug in Qt, but
>> it needs investigation.
> Interesting indeed, I'm not aware of any code in Kate that crease an own
> instance of QStyle. I may be wrong, though...
No no it is definitly not related to kate. Happens in all applications 
(in fact either KApplication or QApplication, last time I checked), I 
just took kate as an example. Could have been okular, or anything. 
You're definitly off the hook !

> Greetings
> Dominik
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