[PyKDE] Using sip with embedded Python

[Phil Thompson]

On Monday 11 August 2003 9:32 pm, David Boddie wrote:
> After lots of experimentation, I've come to the conclusion that I'm
> fundamentally misunderstanding how to use various siplib functions.
>
> In particular, I thought I knew how to use the sipMapCppToSelf function,
> but it appears that the various sipClass_ pointers I'm using are not
> initialised. This might explain the crashes I've been encountering.
>
> In my library I do the following:
>
> 1. I initialise the Python interpreter and import a Python module.
>
> 2. The Python module imports all the modules it needs, including the
>    qt module (which is linked at compile time, but only resolved at
> runtime). (I'm also linking against libsip.so, too).
>
> 3. I attempt to convert a QWidget* (the "parent" variable) to a Python
> object using
>
>    pArg1 = sipMapCppToSelf(parent, sipClass_QWidget);
>
>    (pArg1 is a PyObject*)
>
>    When parent is NULL, this succeeds; otherwise it fails. I discovered
>    that sipClass_QWidget has the value 0 so suspected that sipMapCppToSelf
>    catches the bad parent value normally but gets confused when it has to
>    deal with a NULL sipClass_QWidget value.
>
> The only thing I'm doing to make sipClass_QWidget visible to my library is
> to declare
>
> extern SIP_IMPORT PyObject *sipClass_QWidget;
>
> Am I supposed to perform some sort of initialisation?

The initialisation happens in the call to libqtc.sipRegisterClasses() in
qt.py. Ultimately it is done by sipRegisterClasses().

> Sorry if this is mentioned somewhere in the sources or available
> documentation. If it is then I'd be happy to be redirected to it.

Phil