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

[Rashad Kanavath]

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
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