[PyQt] Segfault when trying
newDoc.setDocumentLayout(QtGui.QPlainTextDocumentLayout(newDoc))
GT6
gt6 at gmx.net
Tue Feb 3 13:13:48 GMT 2009
Phil Thompson wrote:
> On Mon, 02 Feb 2009 16:51:28 +0100, GT6 <gt6 at gmx.net> wrote:
>
>> Phil Thompson wrote:
>>
>>> On Mon, 02 Feb 2009 16:27:51 +0100, GT6 <gt6 at gmx.net> wrote:
>>>
>>>
>>>> Phil Thompson wrote:
>>>>
>>>>
>>>>> On Mon, 02 Feb 2009 13:49:23 +0100, GT6 <gt6 at gmx.net> wrote:
>>>>>
>>>>>
>>>>>
>>>>>> Phil Thompson wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>> On Mon, 02 Feb 2009 03:37:13 +0100, GT6 <gt6 at gmx.net> wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>> Hi there.
>>>>>>>>
>>>>>>>> When running the below sample script, and clicking the button, it
>>>>>>>>
>>>>>>>>
>>> will
>>>
>>>
>>>>>>>> segfault, and I don't understand why or how. I've overwritten a
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>> function
>>>>>
>>>>>
>>>>>
>>>>>>>> in QPlainTextEdit and it should create a new document, set the
>>>>>>>> PlainTextDocumentLayout and then set the document on the
>>>>>>>> QPlainTextEdit
>>>>>>>> widget. The important part is this (1st way):
>>>>>>>>
>>>>>>>> newDoc = QtGui.QTextDocument()
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>> newDoc.setDocumentLayout(QtGui.QPlainTextDocumentLayout(newDoc))
>>>>>
>>>>>
>>>>>
>>>>>>>> self.setDocument(newDoc)
>>>>>>>>
>>>>>>>> The above segfaults. I also tried this (2nd way):
>>>>>>>>
>>>>>>>> newDoc = QtGui.QTextDocument()
>>>>>>>> newDoc.setDocumentLayout(self.documentLayout())
>>>>>>>> self.setDocument(newDoc)
>>>>>>>>
>>>>>>>> This one doesn't segfault, but I get this error:
>>>>>>>>
>>>>>>>> AttributeError: documentLayout
>>>>>>>>
>>>>>>>> Apart from that, I tried this third option (3rd way):
>>>>>>>>
>>>>>>>> newDoc = QtGui.QTextDocument()
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
> newDoc.setDocumentLayout(QtGui.QPlainTextDocumentLayout.__init__(newDoc))
>
>>>
>>>
>>>>>
>>>>>
>>>>>
>>>>>>>> self.setDocument(newDoc)
>>>>>>>>
>>>>>>>> with the only difference from the first one being that __init__ is
>>>>>>>> called explicitly instead of expecting it to be defaultet. This one
>>>>>>>> _doesn't_ segfault, but gives this error:
>>>>>>>>
>>>>>>>> QPlainTextEdit::setDocument: Document set does not support
>>>>>>>> QPlainTextDocumentLayout
>>>>>>>>
>>>>>>>> Which makes no sense as not calling __init__ directly shouldn't be
>>>>>>>>
>>>>>>>>
>>> any
>>>
>>>
>>>>>>>> different than calling it explicitly.
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>> __init__() initialises a class, it doesn't create one.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>> So, does anyone have any idea why
>>>>>>>> this is happening? Do you have a bug tracker?
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>> Keep a reference to "newDoc" - it is getting garbage collected too
>>>>>>> soon.
>>>>>>>
>>>>>>> Phil
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>> Thanks for your help.
>>>>>>
>>>>>> Well, that only works once. So I replace the plzsegfault function in
>>>>>>
>>>>>>
>>> the
>>>
>>>
>>>>>> sample with this (full sample binned here
>>>>>>
>>>>>>
>>>>>>
>>>>> http://rafb.net/p/P6sqML59.html):
>>>>>
>>>>>
>>>>>
>>>>>> def plzsegfault(self):
>>>>>> self.newDoc = QtGui.QTextDocument()
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
> self.newDoc.setDocumentLayout(QtGui.QPlainTextDocumentLayout(self.newDoc))
>
>>>
>>>
>>>>>
>>>>>
>>>>>
>>>>>> # First way
>>>>>> self.setDocument(self.newDoc)
>>>>>>
>>>>>> Then, I can safely click the button once, and it also does what I
>>>>>>
>>>>>>
>>> expect
>>>
>>>
>>>>>> it to do, but clicking the button a second time will again segfault.
>>>>>> What I'm trying to do is that clicking the button will clear the
>>>>>> textfield and make a new document and display it. Do I really have to
>>>>>>
>
>
>>>>>> care about the document names? I *could* implement a counter and have
>>>>>>
>
>
>>>>>> all the documents have different names but I don't really need those
>>>>>> specific names in the future. I just need the textfield to discard
>>>>>>
> the
>
>>>>>> old one and get a new one, everytime the button is clicked. The only
>>>>>> reference to the document that I use lateron is self.document(). I
>>>>>>
>>>>>>
>>> don't
>>>
>>>
>>>>>> need the name...
>>>>>>
>>>>>>
>>>>>>
>>>>> You might not but Python needs a reference of some sort to stop the
>>>>> object
>>>>> being garbage collected.
>>>>>
>>>>> Your new version is still garbage collecting too soon. Just add the
>>>>> following to the end of plzsegfault() in your *original* version...
>>>>>
>>>>> self._doc = newDoc
>>>>>
>>>>> Phil
>>>>>
>>>>>
>>>>>
>>>>>
>>>> It's still not working in my "real" application. I've been trying to
>>>> figure out what's wrong for hours now but it's just weird and I don't
>>>> understand it. Here's the complete code of what I'm doing. It's a small
>>>>
>
>
>>>> calendar: http://rafb.net/p/rW8qrv26.html
>>>>
>>>>
>>> That's got to be the dumbest pasting site I've ever seen. Why isn't
>>>
> there
>
>>> a
>>> link to download a file?
>>>
>>>
>>>
>>>> The code is a bit messy, there are some obsolete things in there. In
>>>>
> any
>
>>>> case, could you please try the following:
>>>>
>>>> 1.) run the script
>>>>
>>>>
>>> I will if you send it to me as an attachment.
>>>
>>> Phil
>>>
>>>
>>>
>> Here you go. Or a direct link: http://stuff.bandruum.ch/pyqal-0.04.py
>>
>
> It's still the same problem. Now that you have multiple documents, using a
> single "self._doc" to keep the reference is no longer adequate. However the
> dict you already have should be used for this.
>
> The attached has a much simplified version of your TextEditEnter class
> which seems to work.
>
> Phil
>
>
Ah well. Nevermind. I changed the implementation completely to use
sqlite now. Still learning all this, but now it's working without
problems as I reuse the same QTextDocument and only handle content. It's
all plain text anyway.
Thanks for your help!
Carl.
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