[Qgis-developer] ownership of QgsMessageBar(-items)

[Marco Bernasocchi]

I'll be in girona from Thursday, let's have a look there.

see ya

ciao

On 24.05.2016 11:58, Nyall Dawson wrote:
> On 24 May 2016 at 19:53, Marco Bernasocchi <marco at opengis.ch> wrote:
>> Hi Richard, I alvays wanted to make a blog post out of this:
>> https://github.com/mbernasocchi/pyqtExperiments/blob/master/qgis_thread_example.py
>>
>> I use message bars in theads there and never had issues.
>>
>> maybe it helps.
> 
> Marco - interesting stuff! Have you seen this PR yet?
> https://github.com/qgis/QGIS/pull/3004
> 
> Looks like we share some common implementation details, so I'd be keen
> to hear your thoughts on that proposed design.
> 
> Nyall
> 
>>
>> ciao
>> Marco
>>
>> On 24.05.2016 10:48, Richard Duivenvoorde wrote:
>>>
>>> Busy with a plugin which retrieves (in separate threads) a lot of data
>>> from 2 w*s services.
>>>
>>> I thought to use the QgsMessageBar to show progress of the (two)
>>> download processes, but stumbled on (I think) a problem:
>>>
>>> - from api docs: https://qgis.org/api/classQgsMessageBar.html#details
>>> The message bar will take ownership of the item...
>>>
>>> My problem now is that (I think) my progressbars (which were place in a
>>> QgsMessageBar-item-widget) are sometimes deleted although I still want
>>> to use them...
>>>
>>> For example: an user can click the little 'x' button in the messagebar
>>> to clean up all messages.
>>> Or a python dev can call 'clean all widgets'.
>>>
>>> BUT at that moment a progressbar part of a messagebaritem is (at least
>>> in cpp world) apparently deleted.
>>> Meaning, if (in the python world) I set a progress value on it, I get a
>>> nice clean segmentation fault....
>>>
>>> I managed to work around this by NOT putting the progress bars in the
>>> messagebar (but put small ones in the plugin toolbar), but as several
>>> examples flow around on Google, I thought to speak out.
>>>
>>> Should we just not let people do this?
>>>
>>> Or was I using the messagebar for things I was not supposed to use if for?
>>>
>>> Or should we make an option to add a 'special' widget to the messagebar,
>>> which is NOT removed using clearWidgets() (either via Python or via
>>> x-button)?
>>>
>>> Regards,
>>>
>>> Richard
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>>
>> --
>> Marco Bernasocchi
>> OPENGIS.ch - berna.io - 27summits.ch
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-- 
Marco Bernasocchi
OPENGIS.ch - berna.io - 27summits.ch