[QGIS-Developer] Making QgsRasterLayerProperties class independent again from QgisApp instance

[Alessandro Pasotti]

On Mon, Sep 23, 2019 at 6:15 PM Vincent Cloarec <vcloarec at gmail.com> wrote:

> Hello,
>
> I have some difficulties in passing the Travis tests with this PR:
> https://github.com/qgis/QGIS/pull/31942.
>
> As I am fed up to make turning the server for nothing and reject CO2, I
> ask for help.
>
> The 'code layout' tests seem not to pass. Reading the log, I can find this
> link http://tinyurl.com/yynt7m9a. Following this link, it seems the
> problems come from warning: undocumented parameters and unknown command
> '\TODO'.
>
> Can anyone confirm ?
>

Confirmed.

You need to complete the documentation of a few methods.
I don't know where the TODO comes from though.



> Thanks.
>
> Vincent Cloarec
> www.reos.site
>
>
> Le lun. 23 sept. 2019 à 00:25, Vincent Cloarec <vcloarec at gmail.com> a
> écrit :
>
>> Hello,
>>
>> Thanks Nyall for your advice.
>>
>> I have chosen to move the raster layer properties to the gui. As the
>> widget is very convenient, no reason to rebuild my own. Moreover, it
>> appears there is not a lot of code to change.
>> So I purpose this PR: https://github.com/qgis/QGIS/pull/31942
>> The tests seem to pass for QGIS, and I have tried to import the
>> QgsRasterLayerProperties class to a standalone application only using the
>> gui library, it is ok.
>>
>> Vincent Cloarec
>> www.reos.site
>>
>>
>> Le jeu. 19 sept. 2019 à 00:37, Nyall Dawson <nyall.dawson at gmail.com> a
>> écrit :
>>
>>> On Thu, 19 Sep 2019 at 13:55, Vincent Cloarec <vcloarec at gmail.com>
>>> wrote:
>>> >
>>> > In standalone applications, I am using the QgsRasterLayerProperties
>>> class to manage rasters displayed in the map canvas.
>>> >
>>> > However, since QGis 3.8, this class is no longer independent from the
>>> QgisApp instance because the methode
>>> QgisApp::instance()->askUserForDatumTransform() is called from the
>>> QgsRasterLayerProperties instance.
>>> >
>>> > As in my standalone applications, I don't have QgsApp instance (no
>>> need), now this applications crash when the raster layer properties widget
>>> opens ...
>>> >
>>> > So, after a look at the Qgis code, I am thinking about to make a PR to
>>> make again the QgsRasterLayerProperties independant from the QgisApp
>>> instance. I think it could be possible with a static method in the QgisApp
>>> class. I have to work on it.
>>>
>>> Possibly -- but it's a band-aid solution only. There's a LOT of code
>>> in the app library which will make assumptions that the QgisApp
>>> instance is available, and that's why all this code is partitioned off
>>> into the app library. app also has no stable API guarantees and you'll
>>> continue to hit situations like this.
>>>
>>> I'd suggest two possible alternative ways forward:
>>>
>>> 1. Use the stable api classes exposes through the gui library to
>>> rebuild your own raster layer properties dialog
>>> 2. Submit a PR moving the raster layer properties class from app ->
>>> gui and adding it to the stable API
>>>
>>> Both approaches are more upfront work, but are paths to much less pain
>>> and future breakage...
>>>
>>> Nyall
>>>
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-- 
Alessandro Pasotti
w3:   www.itopen.it
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