[PyQt] Subclassed QMainWindow is shown and instantly disappear

[Filip Gruszczyński]

I am subclassing QMainWindow to create editors invoked from my browser
application. This goes like this:

action = QAction('Edit', self)
self.connect(action, SIGNAL('triggered()'), resource.invokeEditor)
menu.addAction(action)

for most resources everything is ok and the editor is invoked. But for one:

def invokeEditor(self):
	DocumentEditor(self).show()

the editor is first shown and then hidden again. I was using editor
from PyQt examples (a bit changed). But when I tried it for even a
simple one like this:

class DocumentEditor(QMainWindow):

	def __init__(self, resource):
		QMainWindow.__init__(self)
		print "Initializing Document editor"
		self.__edit = QTextEdit()
		self.setCentralWidget(self.__edit)

I can see, that the editor is invoked, but instantly disappears. I
just can't understand what I am doing suddenly wrong, because for all
other editors (big editor built dynamically from an xml description
and graphical editor for plans) work just fine and never disappear.
What have I forgotten? Do I have to add some parent information?

-- 
Filip Gruszczyński