[Kdenlive-devel] Problems with signals and slots

[Simon Eugster]

Hey Marco,

Thanks! Working here.
Why is the & required? Did you just use trial&error, or is there a
rule that makes sense?

Simon

2010/11/24 Marco Gittler <marco at gitma.de>:
> Hi
>
> I used the new (your) signals with QVector and rewrote the audiosignal.cpp (commited to svn)
>
> regards marco
>
> Am 24.11.2010 um 11:10 schrieb Simon Eugster:
>
>> Well, the «old» signal (using volume) _does_ work, but I cannot explain why.
>> When I try to do the same with my new signal, it does not work.
>>
>> Simon
>>
>> 2010/11/24 Marco Gittler <marco at gitma.de>:
>>> Hi
>>>
>>> I'll change this, to get it working (first on the "old" audiosignal)
>>> You can use this then for your audiospectrum.
>>>
>>>
>>> regards marco
>>>
>>> Am 24.11.2010 um 09:42 schrieb Simon Eugster:
>>>
>>>> Good Morning,
>>>>
>>>> I'm battling around with Qt's signals and slots. In r5116,
>>>> mainwindow.cpp:296 I want to connect my audiospectrum object to
>>>> Render::audioSamplesSignal. But whatever I do, my method never
>>>> receives the signal, although connecting works according to the return
>>>> value, Q_ASSERT etc.
>>>>
>>>> On line 298 I tried to find a reason for it and used the audio volume
>>>> signal. It is defined as:
>>>>  void showAudioSignal(const QByteArray);
>>>> According to the Qt documentation and some people in #qt, Qt uses
>>>> normalizedSignature[1] for signal/slot connections. Meaning that I
>>>> should be able to just use
>>>>  SIGNAL(showAudioSignal(QByteArray))
>>>> to connect the signal. But then connecting fails, telling me that
>>>> there is no such signal.
>>>>
>>>> I do not get an error though when using
>>>>  SIGNAL(showAudioSignal(const QByteArray)
>>>> i.e. the connection is set up correctly. Nevertheless the connected
>>>> slot is never called. Only if I use
>>>>  SIGNAL(showAudioSignal(const QByteArray&)
>>>> connecting works AND the slot gets called. Although the & is not in
>>>> showAudioSignal's signature.
>>>>
>>>> So I tried to use the & for my signal (audioSamplesSignal) as well:
>>>>  audioSamplesSignal(const QVector<int16_t>&,int,int,int)
>>>> with
>>>>  void audioSamplesSignal(const QVector<int16_t>,int,int,int)
>>>> but this fails with «no such signal». Why should I have to add a & for
>>>> a QByteArray, but I'm forbidden to do so for the QVector?
>>>>
>>>> I then tried to change everything (including the signal's signature)
>>>> to const type& (whether making sense or not – what I noticed above
>>>> does not make sense to me anyway). But still, no signal received.
>>>>
>>>> Can anyone help me? Why is qt behaving that way? What is the problem?
>>>>
>>>> thanks
>>>> Simon
>>>>
>>>> [1] http://doc.qt.nokia.com/4.7/qmetaobject.html#normalizedSignature
>>>>
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>>
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>> Increase Visibility of Your 3D Game App & Earn a Chance To Win $500!
>> Tap into the largest installed PC base & get more eyes on your game by
>> optimizing for Intel(R) Graphics Technology. Get started today with the
>> Intel(R) Software Partner Program. Five $500 cash prizes are up for grabs.
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>
>
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> Increase Visibility of Your 3D Game App & Earn a Chance To Win $500!
> Tap into the largest installed PC base & get more eyes on your game by
> optimizing for Intel(R) Graphics Technology. Get started today with the
> Intel(R) Software Partner Program. Five $500 cash prizes are up for grabs.
> http://p.sf.net/sfu/intelisp-dev2dev
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>