Allow certain locator filters to operate on the main thread

Some filters are fast enough to return results that it's overkill
to run them in a background thread - add a flag to these filters
to allow them to run (blocking) in the main thread instead.

python/core/locator/qgslocatorfilter.sip.in

@@ -69,6 +69,13 @@ Abstract base class for filters which collect locator results.
       Lowest
     };
 
+    enum Flag
+    {
+      FlagFast,
+    };
+    typedef QFlags<QgsLocatorFilter::Flag> Flags;
+
+
     QgsLocatorFilter( QObject *parent = 0 );
 %Docstring
 Constructor for QgsLocatorFilter.
@@ -92,6 +99,11 @@ Returns the unique name for the filter. This should be an untranslated string id
 Returns a translated, user-friendly name for the filter.
 
 .. seealso:: :py:func:`name`
+%End
+
+    virtual QgsLocatorFilter::Flags flags() const;
+%Docstring
+Returns flags which specify the filter's behavior.
 %End
 
     virtual Priority priority() const;
@@ -223,6 +235,9 @@ during within their fetchResults() implementation.
 
 };
 
+QFlags<QgsLocatorFilter::Flag> operator|(QgsLocatorFilter::Flag f1, QFlags<QgsLocatorFilter::Flag> f2);
+
+
 
 
 

python/plugins/processing/gui/AlgorithmLocatorFilter.py

@@ -39,7 +39,6 @@ class AlgorithmLocatorFilter(QgsLocatorFilter):
 
     def __init__(self, parent=None):
         super(AlgorithmLocatorFilter, self).__init__(parent)
-        self.found_results = []
 
     def clone(self):
         return AlgorithmLocatorFilter()
@@ -56,7 +55,10 @@ def priority(self):
     def prefix(self):
         return 'a'
 
-    def prepare(self, string, context):
+    def flags(self):
+        return QgsLocatorFilter.FlagFast
+
+    def fetchResults(self, string, context, feedback):
         # collect results in main thread, since this method is inexpensive and
         # accessing the processing registry is not thread safe
         for a in QgsApplication.processingRegistry().algorithms():
@@ -73,11 +75,7 @@ def prepare(self, string, context):
                     result.score = float(len(string)) / len(a.displayName())
                 else:
                     result.score = 0
-                self.found_results.append(result)
-
-    def fetchResults(self, string, context, feedback):
-        for result in self.found_results:
-            self.resultFetched.emit(result)
+                self.resultFetched.emit(result)
 
     def triggerResult(self, result):
         alg = QgsApplication.processingRegistry().createAlgorithmById(result.userData)

src/app/locator/qgsinbuiltlocatorfilters.cpp

@@ -36,10 +36,8 @@ QgsLayerTreeLocatorFilter *QgsLayerTreeLocatorFilter::clone() const
   return new QgsLayerTreeLocatorFilter();
 }
 
-void QgsLayerTreeLocatorFilter::prepare( const QString &string, const QgsLocatorContext & )
+void QgsLayerTreeLocatorFilter::fetchResults( const QString &string, const QgsLocatorContext &, QgsFeedback * )
 {
-  // collect results in main thread, since this method is inexpensive and
-  // accessing the layer tree root is not thread safe
   QgsLayerTree *tree = QgsProject::instance()->layerTreeRoot();
   const QList<QgsLayerTreeLayer *> layers = tree->findLayers();
   for ( QgsLayerTreeLayer *layer : layers )
@@ -51,19 +49,11 @@ void QgsLayerTreeLocatorFilter::prepare( const QString &string, const QgsLocator
       result.userData = layer->layerId();
       result.icon = QgsMapLayerModel::iconForLayer( layer->layer() );
       result.score = static_cast< double >( string.length() ) / layer->layer()->name().length();
-      mResults.append( result );
+      emit resultFetched( result );
     }
   }
 }
 
-void QgsLayerTreeLocatorFilter::fetchResults( const QString &, const QgsLocatorContext &, QgsFeedback * )
-{
-  for ( const QgsLocatorResult &result : qgis::as_const( mResults ) )
-  {
-    emit resultFetched( result );
-  }
-}
-
 void QgsLayerTreeLocatorFilter::triggerResult( const QgsLocatorResult &result )
 {
   QString layerId = result.userData.toString();
@@ -84,11 +74,8 @@ QgsLayoutLocatorFilter *QgsLayoutLocatorFilter::clone() const
   return new QgsLayoutLocatorFilter();
 }
 
-void QgsLayoutLocatorFilter::prepare( const QString &string, const QgsLocatorContext & )
+void QgsLayoutLocatorFilter::fetchResults( const QString &string, const QgsLocatorContext &, QgsFeedback * )
 {
-  // collect results in main thread, since this method is inexpensive and
-  // accessing the project layouts is not thread safe
-
   const QList< QgsMasterLayoutInterface * > layouts = QgsProject::instance()->layoutManager()->layouts();
   for ( QgsMasterLayoutInterface *layout : layouts )
   {
@@ -99,19 +86,11 @@ void QgsLayoutLocatorFilter::prepare( const QString &string, const QgsLocatorCon
       result.userData = layout->name();
       //result.icon = QgsMapLayerModel::iconForLayer( layer->layer() );
       result.score = static_cast< double >( string.length() ) / layout->name().length();
-      mResults.append( result );
+      emit resultFetched( result );
     }
   }
 }
 
-void QgsLayoutLocatorFilter::fetchResults( const QString &, const QgsLocatorContext &, QgsFeedback * )
-{
-  for ( const QgsLocatorResult &result : qgis::as_const( mResults ) )
-  {
-    emit resultFetched( result );
-  }
-}
-
 void QgsLayoutLocatorFilter::triggerResult( const QgsLocatorResult &result )
 {
   QString layoutName = result.userData.toString();
@@ -137,7 +116,7 @@ QgsActionLocatorFilter *QgsActionLocatorFilter::clone() const
   return new QgsActionLocatorFilter( mActionParents );
 }
 
-void QgsActionLocatorFilter::prepare( const QString &string, const QgsLocatorContext & )
+void QgsActionLocatorFilter::fetchResults( const QString &string, const QgsLocatorContext &, QgsFeedback * )
 {
   // collect results in main thread, since this method is inexpensive and
   // accessing the gui actions is not thread safe
@@ -150,14 +129,6 @@ void QgsActionLocatorFilter::prepare( const QString &string, const QgsLocatorCon
   }
 }
 
-void QgsActionLocatorFilter::fetchResults( const QString &, const QgsLocatorContext &, QgsFeedback * )
-{
-  for ( const QgsLocatorResult &result : qgis::as_const( mResults ) )
-  {
-    emit resultFetched( result );
-  }
-}
-
 void QgsActionLocatorFilter::triggerResult( const QgsLocatorResult &result )
 {
   QAction *action = qobject_cast< QAction * >( qvariant_cast<QObject *>( result.userData ) );
@@ -194,7 +165,7 @@ void QgsActionLocatorFilter::searchActions( const QString &string, QWidget *pare
       result.userData = QVariant::fromValue( action );
       result.icon = action->icon();
       result.score = static_cast< double >( string.length() ) / searchText.length();
-      mResults.append( result );
+      emit resultFetched( result );
       found << action;
     }
   }

src/app/locator/qgsinbuiltlocatorfilters.h

@@ -36,15 +36,11 @@ class QgsLayerTreeLocatorFilter : public QgsLocatorFilter
     QString displayName() const override { return tr( "Project Layers" ); }
     Priority priority() const override { return Highest; }
     QString prefix() const override { return QStringLiteral( "l" ); }
+    QgsLocatorFilter::Flags flags() const override { return QgsLocatorFilter::FlagFast; }
 
-    void prepare( const QString &string, const QgsLocatorContext &context ) override;
     void fetchResults( const QString &string, const QgsLocatorContext &context, QgsFeedback *feedback ) override;
     void triggerResult( const QgsLocatorResult &result ) override;
 
-  private:
-
-    QVector< QgsLocatorResult > mResults;
-
 };
 
 class QgsLayoutLocatorFilter : public QgsLocatorFilter
@@ -59,14 +55,11 @@ class QgsLayoutLocatorFilter : public QgsLocatorFilter
     QString displayName() const override { return tr( "Project Layouts" ); }
     Priority priority() const override { return Highest; }
     QString prefix() const override { return QStringLiteral( "pl" ); }
+    QgsLocatorFilter::Flags flags() const override { return QgsLocatorFilter::FlagFast; }
 
-    void prepare( const QString &string, const QgsLocatorContext &context ) override;
     void fetchResults( const QString &string, const QgsLocatorContext &context, QgsFeedback *feedback ) override;
     void triggerResult( const QgsLocatorResult &result ) override;
 
-  private:
-
-    QVector< QgsLocatorResult > mResults;
 };
 
 class QgsActionLocatorFilter : public QgsLocatorFilter
@@ -81,14 +74,13 @@ class QgsActionLocatorFilter : public QgsLocatorFilter
     QString displayName() const override { return tr( "Actions" ); }
     Priority priority() const override { return Lowest; }
     QString prefix() const override { return QStringLiteral( "." ); }
+    QgsLocatorFilter::Flags flags() const override { return QgsLocatorFilter::FlagFast; }
 
-    void prepare( const QString &string, const QgsLocatorContext &context ) override;
     void fetchResults( const QString &string, const QgsLocatorContext &context, QgsFeedback *feedback ) override;
     void triggerResult( const QgsLocatorResult &result ) override;
   private:
 
     QList< QWidget * > mActionParents;
-    QVector< QgsLocatorResult > mResults;
 
     void searchActions( const QString &string, QWidget *parent, QList< QAction *> &found );
 

src/core/locator/qgslocator.cpp

@@ -121,21 +121,31 @@ void QgsLocator::fetchResults( const QString &string, const QgsLocatorContext &c
     }
   }
 
-  QList< QgsLocatorFilter *> clonedFilters;
+  QList< QgsLocatorFilter *> threadedFilters;
   for ( QgsLocatorFilter *filter : qgis::as_const( activeFilters ) )
   {
-    QgsLocatorFilter *clone = filter->clone();
-    connect( clone, &QgsLocatorFilter::resultFetched, clone, [this, filter]( QgsLocatorResult result )
+    std::unique_ptr< QgsLocatorFilter > clone( filter->clone() );
+    connect( clone.get(), &QgsLocatorFilter::resultFetched, clone.get(), [this, filter]( QgsLocatorResult result )
     {
       result.filter = filter;
       emit filterSentResult( result );
-    }, Qt::QueuedConnection );
+    } );
     clone->prepare( searchString, context );
-    clonedFilters.append( clone );
+
+    if ( clone->flags() & QgsLocatorFilter::FlagFast )
+    {
+      // filter is fast enough to fetch results on the main thread
+      clone->fetchResults( searchString, context, feedback );
+    }
+    else
+    {
+      // run filter in background
+      threadedFilters.append( clone.release() );
+    }
   }
 
   mActiveThreads.clear();
-  for ( QgsLocatorFilter *filter : qgis::as_const( clonedFilters ) )
+  for ( QgsLocatorFilter *filter : qgis::as_const( threadedFilters ) )
   {
     QThread *thread = new QThread();
     mActiveThreads.append( thread );
@@ -158,6 +168,9 @@ void QgsLocator::fetchResults( const QString &string, const QgsLocatorContext &c
     connect( thread, &QThread::finished, thread, &QThread::deleteLater );
     thread->start();
   }
+
+  if ( mActiveThreads.empty() )
+    emit finished();
 }
 
 void QgsLocator::cancel()

src/core/locator/qgslocatorfilter.cpp

@@ -27,6 +27,11 @@ QgsLocatorFilter::QgsLocatorFilter( QObject *parent )
 
 }
 
+QgsLocatorFilter::Flags QgsLocatorFilter::flags() const
+{
+  return nullptr;
+}
+
 void QgsLocatorFilter::executeSearchAndDelete( const QString &string, const QgsLocatorContext &context, QgsFeedback *feedback )
 {
   if ( !feedback->isCanceled() )

src/core/locator/qgslocatorfilter.h

@@ -106,6 +106,12 @@ class CORE_EXPORT QgsLocatorFilter : public QObject
       Lowest //!< Lowest priority
     };
 
+    enum Flag
+    {
+      FlagFast = 1 << 1, //!< Filter finds results quickly and can be safely run in the main thread
+    };
+    Q_DECLARE_FLAGS( Flags, Flag )
+
     /**
      * Constructor for QgsLocatorFilter.
      */
@@ -129,6 +135,11 @@ class CORE_EXPORT QgsLocatorFilter : public QObject
      */
     virtual QString displayName() const = 0;
 
+    /**
+     * Returns flags which specify the filter's behavior.
+     */
+    virtual QgsLocatorFilter::Flags flags() const;
+
     /**
      * Returns the priority for the filter, which controls how results are
      * ordered in the locator.
@@ -253,6 +264,8 @@ class CORE_EXPORT QgsLocatorFilter : public QObject
 };
 
 Q_DECLARE_METATYPE( QgsLocatorResult )
+Q_DECLARE_OPERATORS_FOR_FLAGS( QgsLocatorFilter::Flags )
+
 
 #endif // QGSLOCATORFILTER_H
 

src/gui/locator/qgslocatorwidget.cpp

@@ -409,6 +409,11 @@ QgsLocatorFilterFilter *QgsLocatorFilterFilter::clone() const
   return new QgsLocatorFilterFilter( mLocator );
 }
 
+QgsLocatorFilter::Flags QgsLocatorFilterFilter::flags() const
+{
+  return QgsLocatorFilter::FlagFast;
+}
+
 void QgsLocatorFilterFilter::fetchResults( const QString &string, const QgsLocatorContext &, QgsFeedback *feedback )
 {
   if ( !string.isEmpty() )

src/gui/locator/qgslocatorwidget.h

@@ -135,6 +135,7 @@ class QgsLocatorFilterFilter : public QgsLocatorFilter
     QgsLocatorFilterFilter( QgsLocatorWidget *widget, QObject *parent = nullptr );
 
     QgsLocatorFilterFilter *clone() const override SIP_FACTORY;
+    QgsLocatorFilter::Flags flags() const override;
 
     QString name() const override { return QStringLiteral( "filters" );}
     QString displayName() const override { return QString(); }