[Ctk-developers] Q_DISABLE_COPY policy?

[Sascha Zelzer]

Hi,

we also had a short discussion about the Q_DECLARE_PRIVATE macro and 
friends. JC initially used macros and template classes adapted from Qxt 
(the CTK_DECLARE_PRIVATE etc. macros and the ctkPrivate template class). 
I haven't had a look at them in detail yet, so I don't know what their 
benefits are compared to the Qt "native" way.

The only thing about which I am a little bit worried is that 
Q_DECLARE_PRIVATE, Q_D, Q_P, Q_DISABLE_COPY etc. is not public API (e.g. 
it is not documented in the official Qt docs). However, I think many 
people use them and are familiar with them. Shall we use familiar, but 
non-official features of Qt or roll our own macros?


See for example this discussion:

http://lists.trolltech.com/qt-interest/2007-09/thread00325-0.html

The interesting part is:

>  On 14.09.07 13:49:48, Thiago Macieira wrote:
>  >  Note of warning: Q_DECLARE_XXXX are not documented. You're not supposed
>  >  to use them.
>
>  Yet they are documented and advertised to be used on
>  http://techbase.kde.org/Policies/Library_Code_Policy#D-Pointers

Let me put my KDE hat.

===>  KDE developer speaking<===
I know. I wrote that potion of the policy.

KDE is using those macros. KDE is also using other non-documented features and
functions in Qt.
==========

However, as a Trolltech developer, I have to tell you: those macros are
undocumented. Trolltech can change them from one release to the next. What's
more, if you have a problem with them and mail qt-bugs at xxxxxxxxxxxxx or
support at xxxxxxxxxxxxx, the support engineers will tell it's internal API and
they can't help you. (Though, of course, they'll be more polite than me)

KDE is at its own risk doing that. And the side-effects of that have shown up
recently: take a look at this change in that very same page:
http://techbase.kde.org/index.php?title=Policies%2FLibrary_Code_Policy&diff=13707&oldid=13098  <http://techbase.kde.org/index.php?title=Policies%2FLibrary_Code_Policy&diff=13707&oldid=13098>

I removed the notice about QAtomic. Why? Because QAtomic -- an undocumented
class in Qt 4.0 through 4.3 -- has disappeared in Qt 4.4. And KDE is using
it.





On 04/22/2010 08:28 PM, Julien Finet wrote:
> Good idea !
> If we have to follow the Qt naming convention for classes that derive 
> from Qt, then we should probably use the same keywords...
> Julien.
>
> On Thu, Apr 22, 2010 at 2:14 PM, Arnaud GELAS 
> <arnaud_gelas at hms.harvard.edu <mailto:arnaud_gelas at hms.harvard.edu>> 
> wrote:
>
>     Hi,
>
>     I just wanted to know what's the policy for constructor by copy?
>     Do you want to use Q_DISABLE_COPY macro declared in private?
>
>     Arnaud
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>

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