[QGIS-Developer] QGIS3 plugin migration issue

Nyall Dawson nyall.dawson at gmail.com
Tue Apr 3 15:58:50 PDT 2018 

On 4 April 2018 at 05:29, André William <wss.andre at gmail.com> wrote:
> Thank you Nyall, I understand.
> The reason I needed to resize the window was to better fit some image
> content in my HTML help.

My thinking here is whether this needs to be supported officially -
e.g. by making the panel wider by default. Alternatively we could add
a method to QgsProcessingAlgorithmDialogBase to handle resizing of
this panel.

> Taking the opportunity, I'm a C++ and Python developer and I would love to
> contribute on the project. Is there any need for help in the Processing
> Framework (since I'm already a bit familiar with it) or in others areas?

Heck yes! There's a TON of work which processing would greatly benefit
from. Here's a very short brain-dump of potential high-value projects:

- if you're a user of any of the 3rd party providers (GDAL, GRASS,
SAGA), these need a lot of love. There's lots of open tickets against
them, some of which would be quick fixes for someone more familiar
with the underlying provider library. Similarly if you're on Win or
OSX there's quite a few open tickets against these providers (most
testing is done on Linux)

- if you're a model user, a nice project would be improving the inputs
panel in the modeler dialog. It's been discussed (somewhere, can't
find it now) that this panel should be reworked to be a list of inputs
used within the model, with + / - buttons to add a new input and
remove a selected input. And then we could add up/down buttons to
allow inputs to be reordered for models, since they are currently just
shown in a semi-random order and there's no way for users to
reorganize them logically. All the API stuff should be in place for
this, it's just Python GUI work that's needed.

- another high value task is porting the QGIS algorithms from Python
to c++ (for speed and stability). At the same time we do this we
upgrade each algorithm to support "data defined" parameter values
(e.g. buffer width based on expressions!). The goal here is to move
all the QGIS algorithms across to c++, EXCEPT those which have
dependencies on Python libraries.

- there's rough notes on
https://github.com/nyalldawson/QGIS/wiki/Processing-Algorithm-Bugs-and-Enhancements
concerning improvements we can make to existing algorithms which would
be fantastic to see explored

- Or, the funnest processing job, adding more algorithms! There's a
rough wish-list at
https://github.com/nyalldawson/QGIS/wiki/Algorithm-hit-list , some of
which are just a matter of exposing existing QgsGeometry methods as
processing algorithms (e.g. exposing QgsGeometry::transform(
QTransform .... ) as an algorithm to allow rotate/shear/scale
transforms), and some of which require adding wrappers to GEOS
functions to QgsGeometry (GEOSMinimumWidth_r,
GEOSMinimumClearanceLine_r, GEOSNode_r, GEOSSharedPaths_r) and then
exposing as processing algorithms. Others need javascript->c++ ports
of functionality from turf/mapbox js libraries, if that kind of thing
interests you.

> I would probably need some guidance at first but I've been using QGIS and
> developing plugins for some time now, so I guess it wouldn't be too big a
> learning curve.

I'm happy to mentor. Just let me know.

Nyall


>
> André
>
> 2018-04-03 0:29 GMT-03:00 Nyall Dawson <nyall.dawson at gmail.com>:
>>
>> On 31 March 2018 at 14:06, André William <wss.andre at gmail.com> wrote:
>> > After some digging, I found that while the textShortHelp object is not
>> > directly available in the AlgorithmDialog class anymore, i was able to
>> > access it like this:
>> >>
>> >> shortHelpObj = dlg.findChild(QTextBrowser, 'textShortHelp')
>> >
>> > Is this the expected behavior?
>>
>> None of this is in stable API, so can change between QGIS versions
>> (including within minor versions/patch releases).
>>
>> Stable API for processing is:
>> - the classes within the core library (unless they are explicitly
>> marked as non-stable, e.g.  the modeler related classes)
>> - the base GUI "WidgetWrapper" class (NOT any of its subclasses)
>> - some methods from the processing namespace:
>>     - processing.algorithmHelp()
>>     - processing.run()
>>     - processing.runAndLoadResults()
>>     - processing.createAlgorithmDialog()
>>     - processing.execAlgorithmDialog()
>>
>> So, in short, unfortunately this approach is always going to be
>> fragile. Better wrap it in a big try block! ;)
>>
>> I gather you're trying to force the "help" panel to resize when the
>> dialog is opened. Is there a particular reason why you need to do
>> this?
>>
>> Nyall
>>
>>
>> >
>> > André W.
>> >
>> > 2018-03-30 18:54 GMT-03:00 André William <wss.andre at gmail.com>:
>> >>
>> >> Hi all,
>> >>
>> >> I'm porting an existing Geoprocessing Algorithm plugin to QGIS 3 and
>> >> I'm
>> >> having some trouble customizing the default dialog.
>> >> On QGIS 2.x the following code worked:
>> >>
>> >>> class TestAlgorithm(GeoAlgorithm):
>> >>>     INPUT = 'INPUT'
>> >>>     OUTPUT = 'OUTPUT'
>> >>>
>> >>>
>> >>>
>> >>>     def getCustomParametersDialog(self):
>> >>>         customDialog = AlgorithmDialog(self)
>> >>>         customDialog.textShortHelp.setFixedWidth(450)
>> >>>         return customDialog
>> >>
>> >>
>> >> On QGIS 3 however, the getCustomParametersDialog() method is gone. I
>> >> assumed it was replaced by the new createCustomParametersWidget(), but
>> >> unfortunately this method doesn't seem to get called by the parent
>> >> class:
>> >>
>> >>>     def createCustomParametersWidget(self, parent):
>> >>>         customDialog = AlgorithmDialog(self)
>> >>>         customDialog.textShortHelp.setFixedWidth(450)
>> >>>         return customDialog
>> >>
>> >>
>> >> I also tried manually creating the dialog, but I get a message saying
>> >> that
>> >> the 'AlgorithmDialog' object has no attribute 'textShortHelp'.
>> >>
>> >>> alg =
>> >>>
>> >>> QgsApplication.processingRegistry().algorithmById('test:testAlgorithm')
>> >>> dlg = AlgorithmDialog(alg)
>> >>> dlg.textShortHelp.setFixedWidth(450)
>> >>> dlg.show()
>> >>
>> >>
>> >> Any thoughts?
>> >>
>> >> Thanks in advance!
>> >> André
>> >
>> >
>> >
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>

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