[PyQt] An issue with calling back into the Python interpreter from C from inside of PyQt...
rjfrank at ensight.com
Mon Jul 25 23:07:09 BST 2011
This one has been a little perplexing, so I thought
I'd run it past folks here to see if they had any suggestions.
It is a little complex, but let me try to describe the setup.
I have an embedded Python interpreter with PyQt installed
in it. My application itself is Qt/C++, but some portions
of the GUI are written in Python/PyQt. In general, this
works really well. My app also has a module that allows
Python code to make calls into it. Here is my problem.
I have PyQt class that looks like:
from PyQt4 import QtGui, QtCore
self._ext = None
self._ext = ext
def startDrag(self, actions):
mime = self._ext.dragBuildMIME("currentitem")
drag = QtGui.QDrag(self)
'ext' is a module that calls back into my C code
that creates a somewhat specialized QMimeData
instance (it puts in some extra formats). Now,
on the drag operation, I have a QWidget subclass
that allows drops (EnsCvfWidget). I get to my
void EnsCvfWidget::dropEvent ( QDropEvent * event )
just fine and can crack open the QMimeData object
and see that it came from CeiStyleListWidget.
Now, to complete the action, I call back out to
the Python doDrag() method on the CeiStyleListWidget
instance using: PyObject_Call() from my C++ code in
the dropEvent method. This crashes the Python
interpreter in a bad way (note: if I make the call
to doDrag from C++ directly, the call works fine).
It looks like some sort of Python interpreter
re-entrancy issue. When I add a call to check
the thread state:
PyThreadState *tstate = PyThreadState_GET();
My PyObject_Call() only works if tstate does not
return NULL. In the drag/drop callback stack, it
always seems to be NULL.
First, should this work? Can I call drag.exec_()
from Python and then in the dropEvent method (on an
Qt object written in C++) be able to call a method
on the Python object using PyObject_Call()? If not,
can I do so with some other method?
I know the question is a little dense, but if I can
clarify any of it for you, please let me know.
Thanks in advance for considering my problem!
rjf Quando omni flunkus moritati
Randall Frank rjfrank at ensight.com 919-363-0883
Computational Engineering International www.ceintl.com
2166 North Salem St, Suite 101, Apex, NC 27523-6456
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