[PyQt] QSettings.registerFormat unavailable in PyQt4?

[Phil Thompson]

On Sat, 06 Jun 2009 02:56:55 +0200, Giovanni Bajo <rasky at develer.com>
wrote:
> On Sat, 6 Jun 2009 01:19:39 +0200, David Boddie <david at boddie.org.uk>
> wrote:
>> On Fri Jun 5 19:25:01 BST 2009, Giovanni Bajo wrote:
>> 
>>> On 6/4/2009 10:18 PM, Phil Thompson wrote:
>> 
>>> > It can't be wrapped because of the nature of the function pointer
>>> > arguments - bad API design.
>>>
>>> Is it the same with Jambi?
>> 
>> I think so - look here:
>> 
>>
>
http://doc.trolltech.com/qtjambi-4.5.0_01/com/trolltech/qt/core/QSettings.html
> 
> Given that there is no way to unregister a format, I think that there is
a
> way to wrap it for PyQt: just prepare a fixed number of clones of global
> read/write functions, that retrieve Python's callable objects from a
> fixed-size global array. Each time registerFormat() is used, save the
read
> and write function callables into the global arrays (incref'ing them
> forever, and using an ever growing counter that says how many custom
> formats have been registered); then, call the C++ version and pass it the
> pointers to the correct couple of clones of the global read/write
> functions.

How do you identify the correct couple of clones?

There's no problem with wrapping function pointers in themselves. What's
missing is that those functions should also take the QSettings::Format as
an additional parameter. A good API will allow you to use a single callback
in all situations which requires that the callback is passed something that
allows it to identify the particular context.

Phil