Make QgsProcessingAlgRunnerTask work correctly

It now safely can execute algorithms in background threads without issues
qgis · Jul 6, 2017 · e1184cd · e1184cd
1 parent e5b156b
commit e1184cd
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Showing 3 changed files with 24 additions and 9 deletions.
diff --git a/python/core/processing/qgsprocessingalgrunnertask.sip b/python/core/processing/qgsprocessingalgrunnertask.sip
@@ -33,6 +33,15 @@ class QgsProcessingAlgRunnerTask : QgsTask
 
     virtual void cancel();
 
+  signals:
+
+    void executed( bool successful, const QVariantMap &results );
+%Docstring
+ Emitted when the algorithm has finished execution. If the algorithm completed
+ execution without errors then ``successful`` will be true. The ``results`` argument
+ contains the results reported by the algorithm.
+%End
+
   protected:
 
     virtual bool run();

diff --git a/src/core/processing/qgsprocessingalgrunnertask.cpp b/src/core/processing/qgsprocessingalgrunnertask.cpp
@@ -24,7 +24,6 @@
 
 QgsProcessingAlgRunnerTask::QgsProcessingAlgRunnerTask( const QgsProcessingAlgorithm *algorithm, const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
   : QgsTask( tr( "Running %1" ).arg( algorithm->name() ), QgsTask::CanCancel )
-  , mParameters( parameters )
   , mContext( context )
   , mFeedback( feedback )
   , mAlgorithm( algorithm->create() )
@@ -34,6 +33,8 @@ QgsProcessingAlgRunnerTask::QgsProcessingAlgRunnerTask( const QgsProcessingAlgor
     mOwnedFeedback.reset( new QgsProcessingFeedback() );
     mFeedback = mOwnedFeedback.get();
   }
+  if ( !mAlgorithm->prepare( parameters, context, mFeedback ) )
+    cancel();
 }
 
 void QgsProcessingAlgRunnerTask::cancel()
@@ -47,7 +48,7 @@ bool QgsProcessingAlgRunnerTask::run()
   bool ok = false;
   try
   {
-    mResults = mAlgorithm->run( mParameters, mContext, mFeedback, &ok );
+    ok = mAlgorithm->runPrepared( mContext, mFeedback );
   }
   catch ( QgsProcessingException & )
   {
@@ -59,12 +60,9 @@ bool QgsProcessingAlgRunnerTask::run()
 void QgsProcessingAlgRunnerTask::finished( bool result )
 {
   Q_UNUSED( result );
-  if ( !mResults.isEmpty() )
+  if ( result )
   {
-    QgsMapLayer *layer = QgsProcessingUtils::mapLayerFromString( mResults.value( "OUTPUT_LAYER" ).toString(), mContext );
-    if ( layer )
-    {
-      mContext.project()->addMapLayer( mContext.temporaryLayerStore()->takeMapLayer( layer ) );
-    }
+    mResults = mAlgorithm->postProcess( mContext, mFeedback );
   }
+  emit executed( result, mResults );
 }
diff --git a/src/core/processing/qgsprocessingalgrunnertask.h b/src/core/processing/qgsprocessingalgrunnertask.h
@@ -49,14 +49,22 @@ class CORE_EXPORT QgsProcessingAlgRunnerTask : public QgsTask
 
     virtual void cancel() override;
 
+  signals:
+
+    /**
+     * Emitted when the algorithm has finished execution. If the algorithm completed
+     * execution without errors then \a successful will be true. The \a results argument
+     * contains the results reported by the algorithm.
+     */
+    void executed( bool successful, const QVariantMap &results );
+
   protected:
 
     virtual bool run() override;
     virtual void finished( bool result ) override;
 
   private:
 
-    QVariantMap mParameters;
     QVariantMap mResults;
     QgsProcessingContext &mContext;
     QgsProcessingFeedback *mFeedback = nullptr;