[Qgis-developer] Re : [Qgis-user] Pyqt4 : which signal is sent when dialog comes to foreground?

Matthias Kuhn matthias at opengis.ch
Mon Apr 6 13:11:58 PDT 2015 

Hi Junior,

The following lines work for a short test-case.

def compAdded( composer ):
  print composer

def compRemoved( composer ):
  print composer

iface.composerAdded.connect( compAdded )
iface.composerRemoved.connect( compRemoved )

It is possible that the QueuedConnection crashes because along with it a
composer is emitted which at the time the slot is executed is already
deleted. That was only a possible approach which I did not test and
reading your report seems unstable.

Matthias

On 04/06/2015 12:33 AM, Junior Delaz wrote:
> Hi,
> I do understand nothing.
> After I read your message, Matthias, I told myself that using QT.
> QueuedConnection should be the easiest way. Then i wrote
> self.iface.composerWillBeRemoved.connect(self.refreshList,
> Qt.QueuedConnection)
> But each time i delete a composer, QGIS crashes.
> So I've spent the week on reading about Qt.QueuedConnection and then
> signal and slots, function partial, QSignalMapper, sender trying to
> understand how I can catch the sender and manage to update my list.
> All this without success in the code.
> And today, I tried again Qt.QueuedConnection, QGIS crashed. Without
> any changes, I tried again and it worked and continues to work. Adding
> and deleting composer in the composer manager echoes in my list.
> I hope it will remain like that.
>
> But now I realize that I didn't take into account the renaming of a
> composer. :(
>
> I think I'd wisely keep the refreshlist button unless someone tells me
> how I can reach the composer manager dialog programmatically. So that
> I will try to synchronize my list with its widgetlistitems...
>
> Thanks for all...
>
>
> 2015-03-31 14:50 GMT+02:00 Matthias Kuhn <matthias at opengis.ch
> <mailto:matthias at opengis.ch>>:
>
>     You should get a parameter containing the composer that is being
>     deleted with composerWillBeRemoved signal. Try to use that to
>     infer which composer has been removed. As the signal name
>     indicates, at the time it is emitted, the composer is not deleted yet.
>     As an alternative you may make the connection with
>     Qt.QueuedConnection. It is possible that with this connection
>     style you will receive the signal after deletion and are able to
>     continue using your current update method.
>
>     Best
>     Matthias
>
>
>     On 03/31/2015 02:04 PM, Junior Delaz wrote:
>>     Matthias,
>>     Thanks. I just give it a try it and all goes well with
>>     composerAdded.
>>     But not really well with composerWillBeRemoved signal. The first
>>     deletion in the composer manager does nothing and deleting a
>>     second composer does remove the first one in my list. and so on...
>>     My update function should be rewritten I think.  I'll try to see
>>     how improving it and may (surely) ask again for help (if needed).
>>
>>     While seeking information about composerWillBeRemoved, I found a
>>     composerRemoved [1] [2] signal (that doesn't appear in the API
>>     doc) and without being able to use it. :(
>>     [1]
>>     https://github.com/qgis/QGIS/blob/master/src/app/composer/qgscomposermanager.cpp
>>     (line 48
>>     [2] https://github.com/qgis/QGIS/blob/master/src/app/qgisapp.cpp
>>     (line 5601)
>>
>>     Another thing that may not be related : what the
>>     deletePrintComposers function
>>     (https://github.com/qgis/QGIS/blob/master/src/app/qgisapp.cpp
>>     line 5698) is for?
>>
>>     Thanks again for the clue.
>>
>>     2015-03-31 9:43 GMT+02:00 Matthias Kuhn <matthias at opengis.ch
>>     <mailto:matthias at opengis.ch>>:
>>
>>         QgisInterface (iface) has a composerAdded and
>>         composerWillBeRemoved signal.
>>
>>         Did you try to connect to these?
>>
>>         Best,
>>         Matthias
>>
>>
>>         On 03/31/2015 09:34 AM, Junior wrote:
>>>         Hi all, Luca
>>>         Thanks for answering. But i already have an update function
>>>         that I linked to an update list button. I even linked it to
>>>         the icon on the toolbar so that when user calls foreground
>>>         the dialog it's already updated.
>>>         The case I'd like to manage: user can open plugin dialog and
>>>         composer manager. The two dialogs are visible (to the eyes)
>>>         even though composer manager is the one at foreground. He
>>>         makes changes and directly clicked on the plugin dialog. He
>>>         should update list but if he forgets and executes, this may
>>>         lead to bug I don't want to / can't yet manage.
>>>         Reason why I want to ensure that list is always up to date
>>>         when he interacts with the dialog
>>>
>>>         Envoyé depuis mon HTC
>>>
>>>         ----- Reply message -----
>>>         De : "Luca Manganelli" <luca76 at gmail.com>
>>>         <mailto:luca76 at gmail.com>
>>>         Pour :
>>>         Cc : "qgis-user at lists.osgeo.org"
>>>         <mailto:qgis-user at lists.osgeo.org>
>>>         <qgis-user at lists.osgeo.org>
>>>         <mailto:qgis-user at lists.osgeo.org>, "qgis-developer"
>>>         <qgis-developer at lists.osgeo.org>
>>>         <mailto:qgis-developer at lists.osgeo.org>
>>>         Objet : [Qgis-developer] [Qgis-user] Pyqt4 : which signal is
>>>         sent when dialog comes to foreground?
>>>         Date : mar., mars 31, 2015 07:56
>>>
>>>         On Mon, Mar 30, 2015 at 6:12 PM, Junior Delaz <delazj at gmail.com> <mailto:delazj at gmail.com> wrote:
>>>         > I've read about defining a custom showEvent function but can't understand
>>>         > where to put it and what inside.
>>>         > If somebody can give some tips...
>>>
>>>         You could add a "Update list" button
>>>         _______________________________________________
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>>>
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>>
>>
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>>
>
>

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