[Development] QProperty and library coding guide

André Somers andre at familiesomers.nl
Mon Jul 20 06:46:08 CEST 2020

On 16-07-2020 13:08, Edward Welbourne wrote:
> Il 16/07/20 12:43, Volker Hilsheimer ha scritto:
>>> For pre-C++20 (where it’s possible to have zero-size structs), and
>>> for compilers that don’t respect the [[no_unqiue_address]] attribute,
>>> all these struct-instances are put into a union. In that case, a
>>> class using QProperty will be larger (by the same amount no matter
>>> the number of properties) than the same class in Qt 5. With C+++ 20
>>> and compilers that do respect [[no_unique_address]], the size and
>>> layout of these classes will be the same.
> Giuseppe D'Angelo (16 July 2020 12:58) requested:
>> Could anyone please illustrate with some code snippets how to achieve
>> this, in practice, in a number of use cases? E.g. client code (non
>> pimpled QObject subclass), (Qt) library code (pimpled QObject
>> subclass), etc.; gadgets (does QProperty work there?); with and
>> without other Q_PROPERTY/QProperty already present, etc.
> As noted in my last mail, documentation is still lagging.  Several of us
> - previously ignorant of the new system - are currently helping Ulf and
> Fabian with conversion.  We are, in the process, helping to debug the
> draft instructions for how to convert and point out gaps in the system
> that make this harder than it should be.  Hopefully, once we've spent a
> week or two hassling Ulf and Fabian with questions, they'll have the
> right things in place and know how to document it clearly.  However,
> doing so today would soak up some of their time that is better spent
> getting the system into the right state so that the documentation
> doesn't need repeated updates ...
> Please be patient, we are working on this,

Please understand that waiting with this will also make other 
contributors who will need to deal with QProperty wait, including those 
who will need to OK such changes (such as Thiago). So, you are making 
dozens of people wait to protect the time of two people? That doesn't 
make much sense IMO. All that was asked for were some examples, not 
fully fledged detailed documentation.



> 	Eddy.
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