[PyQt] return value from QGraphicsItem::itemChange is not handled properly.

[Yann Le Hir]

Hi,

I'm having an issue with QGraphicsItem::itemChange.

Here is the test program :

import PyQt5.Qt  as     qt

class Node( qt.QGraphicsRectItem ) :
    def __init__( self , sector ) :
        super( Node , self ).__init__( sector )

    def itemChange( self , change , v ) :
        res = super( Node , self ).itemChange( change , v )
        print "itemChange return value : ",res
        return res

b = qt.QGraphicsLineItem()
c = qt.QGraphicsLineItem()
a = Node(b)
print a.parentItem(),b
a.setParentItem(c)
print a.parentItem(), c


I get this output :
<PyQt5.QtWidgets.QGraphicsLineItem object at 0x8f9f194> 
<PyQt5.QtWidgets.QGraphicsLineItem object at 0x8f9f194>
itemChange return value :  <PyQt5.QtWidgets.QGraphicsLineItem object at 
0x8f9f1dc>
itemChange return value :  <PyQt5.QtWidgets.QGraphicsLineItem object at 
0x8f9f1dc>
None <PyQt5.QtWidgets.QGraphicsLineItem object at 0x8f9f1dc>

If I remove itemChange, I get this output :
<PyQt5.QtWidgets.QGraphicsLineItem object at 0xf2e6814c> 
<PyQt5.QtWidgets.QGraphicsLineItem object at 0xf2e6814c>
<PyQt5.QtWidgets.QGraphicsLineItem object at 0xf2e68194> 
<PyQt5.QtWidgets.QGraphicsLineItem object at 0xf2e68194>

I'm using PyQt-5.0, Sip 4.14.7 and Qt 5.1.0
I tried with PyQt-5.0.1, sip 4.15.1 and Qt 5.1.0 without change.

I digged into this, basically when setParentItem is called itemChange is called 
on this item and use the return value of itemChange to set the parent.
In C itemChange returns a QVariant, which must be casted as a QGraphicsItem to 
be set as a parent.
This took me to the Chimera::parse_py_type function. Apparently, someone (QT?) 
registers QGraphicsItem as a QMetaType, but not QGraphicsLineItem.

If I replace :
_metatype = QMetaType::type(_name.constData());
By :
if(strcmp(_name.constData(),"QGraphicsLineItem*")==0)
    _metatype = QMetaType::type("QGraphicsItem*");
else
    _metatype = QMetaType::type(_name.constData());

(I know how bad this is, but it's for demonstration purpose.)

The output of the test program is then :
<PyQt5.QtWidgets.QGraphicsLineItem object at 0x89ba194> 
<PyQt5.QtWidgets.QGraphicsLineItem object at 0x89ba194>
itemChange return value :  <PyQt5.QtWidgets.QGraphicsLineItem object at 
0x89ba1dc>
itemChange return value :  <PyQt5.QtWidgets.QGraphicsLineItem object at 
0x89ba1dc>
<PyQt5.QtWidgets.QGraphicsLineItem object at 0x89ba1dc> 
<PyQt5.QtWidgets.QGraphicsLineItem object at 0x89ba1dc>

Any ideas on how to fix this properly ?

Regards,
Yann.

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