[QGIS-Developer] only read name and group name of processing algorithms during startup

[Rashad Kanavath]

Nyall,

could we have defineCharacteristicsFromFile method in
QgsProcessingAlgorithm ?.
the diff with canExecute is more of a working draft.



On Thu, Mar 15, 2018 at 03:27:50PM +0100, Rashad Kanavath wrote:
> Hello,
> 
> On Wed, Mar 14, 2018 at 4:38 AM, Nyall Dawson <nyall.dawson at gmail.com>
> wrote:
> 
> > On 13 March 2018 at 20:56, Rashad Kanavath <rashad.kanavath at c-s.fr> wrote:
> > > if a provier is enabled then qgis reads all algorithm's during
> > > startup. This involves reading descriptor files and doing all parsing
> > > required to make gui when user actually open algorithm (click on
> > > treeitem).
> > > So If I have like three provider enabled it takes more time to start
> > qgis than
> > > usual. Even though, I might open one or two later at some point.
> > >
> > > It is not necessary here to parse "all" data during startup.  name and
> > > group name is only needed to fill provider-algorithm tree. This is
> > > true for any provider which uses descriptor files (OTB, GRASS, SAGA
> > etc..).
> >
> > Actually it's a bit trickier here -- models make things more complex
> > as they self-validate on creation, and need full knowledge of the
> > dependent algorithm's parameters and outputs.
> >
> 
> Yes. there are different cases like modeler, standard, batch, scripts.
> I tried to utilize canExecute() in otb and seems to be working.
> You already have a very flexible, strong API in qgis processing such
> trickier feature like this one has become too easy!!.
> 
> I had to call alg.canExecute() in two places and that's it.
> diff attached below. With this loading time will be hopefully improved for
> OTB, SAGA, GRASS GIS.
> 
> index f5bdc40dc5..1cca57769a 100644
> --- a/python/plugins/processing/modeler/ModelerParametersDialog.py
> +++ b/python/plugins/processing/modeler/ModelerParametersDialog.py
> @@ -70,6 +70,7 @@ class ModelerParametersDialog(QDialog):
>          QDialog.__init__(self)
>          self.setModal(True)
>          # The algorithm to define in this dialog. It is an instance of
> QgsProcessingModelAlgorithm
> +        alg.canExecute()
>          self._alg = alg
>          # The model this algorithm is going to be added to
>          self.model = model
> @@ -80,6 +81,9 @@ class ModelerParametersDialog(QDialog):
>          settings = QgsSettings()
>          self.restoreGeometry(settings.value("/Processing/
> modelParametersDialogGeometry", QByteArray()))
> 
> +    def algorithm(self):
> +        return self._alg
> +
>      def closeEvent(self, event):
>          settings = QgsSettings()
>          settings.setValue("/Processing/modelParametersDialogGeometry",
> self.saveGeometry())
> @@ -242,7 +246,6 @@ class ModelerParametersDialog(QDialog):
>              outTypes = []
>          elif not isinstance(outTypes, (tuple, list)):
>              outTypes = [outTypes]
> -
>          return self.model.availableSourcesForChild(self.childId,
> [p.typeName() for p in paramType if
> 
>  issubclass(p, QgsProcessingParameterDefinition)],
>                                                     [o.typeName() for o in
> outTypes if
> diff --git a/src/core/processing/models/qgsprocessingmodelchildalgorithm.cpp
> b/src/core/processing/models/qgsprocessingmodelchildalgorithm.cpp
> index f5f8074c88..01906a7f62 100644
> --- a/src/core/processing/models/qgsprocessingmodelchildalgorithm.cpp
> +++ b/src/core/processing/models/qgsprocessingmodelchildalgorithm.cpp
> @@ -58,7 +58,7 @@ QgsProcessingModelChildAlgorithm &
> QgsProcessingModelChildAlgorithm::operator=( c
> 
>  const QgsProcessingAlgorithm *QgsProcessingModelChildAlgorithm::algorithm()
> const
>  {
> -  return mAlgorithm.get();
> +  return mAlgorithm && mAlgorithm->canExecute() ? mAlgorithm.get():
> nullptr;
>  }
> 
>  void QgsProcessingModelChildAlgorithm::setModelOutputs( const
> QMap<QString, QgsProcessingModelOutput> &modelOutputs )
> 
> test code for otb provider:
> https://gitlab.orfeo-toolbox.org/orfeotoolbox/qgis-otb-plugin
> I can add modification to SAGA and GRASS if you are okay to move this to PR.
> 
> 
> > > Issue is more about calling defineDescriptorFile() in Algorithm's
> > > __init__ method. And ofcourse, one cannot avoid init when adding
> > > algorithm and tree need to add an instance of algorithm. what can be
> > > done?
> >
> > What I've been thinking/planning is to take advantage of task manager
> > here. So basically:
> >
> > - on processing startup, there's no providers added
> > - when the qgis interface is fully loaded then we fire up a background
> > task which loads the providers, allowing them to fully build their
> > available algorithms and parameters without blocking the startup
> > - after the task completes, the tree is populated
> >
> 
> this is still loading all algorithm with parsing but things will be in
> background to not block ui for users. correct?
> In that case, you could include above diff and then add loading in
> background task. IMHO that will be best.
> 
> 
> > I'd like to see more plugins take this approach, so that qgis can load
> > nice and quick and the slow stuff happens without annoying users...
> >
> > Nyall
> > _______________________________________________
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> >
> 
> 
> 
> -- 
> Regards,
>    Rashad

-- 
Take care,
Rashad