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List:       pykde
Subject:    Re: [PyQt] Inconsistent behavior with multiple inheritance and ConvertToSubClassCode
From:       Phil Thompson <phil () riverbankcomputing ! com>
Date:       2018-09-30 12:46:21
Message-ID: AD4CFA5C-63FD-411D-880D-492878B95C72 () riverbankcomputing ! com
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On 25 Sep 2018, at 8:10 am, Nyall Dawson <nyall.dawson@gmail.com> wrote:
> 
> Hi list,
> 
> I've been struggling for a while with some inconsistent behavior
> relating to ConvertToSubClassCode and a multiple inherited class.
> 
> The definition currently looks something like:
> 
> 
> class LayoutItem : LayoutObject, QGraphicsRectItem
> {
> %TypeHeaderCode
> #include "layoutitem.h"
> #include "layoutitempicture.h"
> #include "layoutitemlabel.h"
> %End
> %ConvertToSubClassCode
> // the conversions have to be static, because they're using
> multiple inheritance
> // (seen in PyQt4 .sip files for some QGraphicsItem classes)
> switch ( sipCpp->type() )
> {
> case QGraphicsItem::UserType + 104:
> sipType = sipType_LayoutItemPicture;
> *sipCppRet = static_cast<LayoutItemPicture *>( sipCpp );
> break;
> case QGraphicsItem::UserType + 105:
> sipType = sipType_LayoutItemLabel;
> *sipCppRet = static_cast<LayoutItemLabel *>( sipCpp );
> break;
> default:
> sipType = 0;
> }
> %End
> public:
> ...
> 
> 
> While this... sometimes... works correctly, most often LayoutItem
> subclasses are not automatically cast to the subclass, and remain as
> LayoutItems only. Is the ConvertToSubClassCode incorrect here?

There is nothing obviously wrong. You probably need to put in debug statements to \
work out exactly what is happening.

Phil
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