Send feature counting to background task

python/core/core.sip

@@ -165,6 +165,7 @@
 %Include qgsvectorlayercache.sip
 %Include qgsvectorlayereditbuffer.sip
 %Include qgsvectorlayereditpassthrough.sip
+%Include qgsvectorlayerfeaturecounter.sip
 %Include qgsvectorlayerimport.sip
 %Include qgsvectorlayerjoinbuffer.sip
 %Include qgsvectorlayerjoininfo.sip

python/core/qgsvectorlayer.sip

@@ -841,7 +841,7 @@ Return the provider type for this layer
 .. versionadded:: 2.10
 %End
 
-    bool countSymbolFeatures( bool showProgress = true );
+    bool countSymbolFeatures();
 %Docstring
  Count features for symbols. Feature counts may be get by featureCount().
  \param showProgress show progress dialog
@@ -2000,6 +2000,12 @@ Signal emitted when setLayerTransparency() is called
 .. versionadded:: 3.0
 %End
 
+    void symbolFeatureCountMapChanged();
+%Docstring
+ Emitted when the feature count for symbols on this layer has been recalculated.
+
+.. versionadded:: 3.0
+%End
 
   protected:
     virtual void setExtent( const QgsRectangle &rect );

python/core/qgsvectorlayerfeaturecounter.sip

@@ -0,0 +1,45 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/qgsvectorlayerfeaturecounter.h                              *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+class QgsVectorLayerFeatureCounter : QgsTask
+{
+%Docstring
+
+ Counts the features in a QgsVectorLayer in task.
+ You should most likely not use this directly and instead call
+ QgsVectorLayer.countSymbolFeatures() and connect to the signal
+ QgsVectorLayer.symbolFeatureCountMapChanged().
+
+.. versionadded:: 3.0
+%End
+
+%TypeHeaderCode
+#include "qgsvectorlayerfeaturecounter.h"
+%End
+  public:
+
+    QgsVectorLayerFeatureCounter( QgsVectorLayer *layer );
+%Docstring
+ Create a new feature counter for ``layer``.
+%End
+
+    virtual bool run();
+
+  signals:
+    void symbolsCounted( const QHash<QString, long> &symbolFeatureCountMap );
+
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/qgsvectorlayerfeaturecounter.h                              *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/

src/core/CMakeLists.txt

@@ -263,6 +263,7 @@ SET(QGIS_CORE_SRCS
   qgsvectorfilewriter.cpp
   qgsvectorfilewritertask.cpp
   qgsvectorlayer.cpp
+  qgsvectorlayerfeaturecounter.cpp
   qgsvectorlayercache.cpp
   qgsvectorlayerdiagramprovider.cpp
   qgsvectorlayereditbuffer.cpp
@@ -569,6 +570,7 @@ SET(QGIS_CORE_MOC_HDRS
   qgsvectorlayereditbuffer.h
   qgsvectorlayereditpassthrough.h
   qgsvectorlayer.h
+  qgsvectorlayerfeaturecounter.h
   qgsvectorlayerjoinbuffer.h
   qgsvectorlayertools.h
   qgsmapthemecollection.h

src/core/qgsvectorlayer.cpp

@@ -71,6 +71,7 @@
 #include "qgsvectorlayerlabeling.h"
 #include "qgsvectorlayerrenderer.h"
 #include "qgsvectorlayerundocommand.h"
+#include "qgsvectorlayerfeaturecounter.h"
 #include "qgspointv2.h"
 #include "qgsrenderer.h"
 #include "qgssymbollayer.h"
@@ -83,6 +84,7 @@
 #include "qgsfeedback.h"
 #include "qgsxmlutils.h"
 #include "qgsunittypes.h"
+#include "qgstaskmanager.h"
 
 #include "diagram/qgsdiagram.h"
 
@@ -126,6 +128,7 @@ typedef bool deleteStyleById_t(
   QString &errCause
 );
 
+
 QgsVectorLayer::QgsVectorLayer( const QString &vectorLayerPath,
                                 const QString &baseName,
                                 const QString &providerKey,
@@ -674,7 +677,7 @@ class QgsVectorLayerInterruptionCheckerDuringCountSymbolFeatures: public QgsInte
     QProgressDialog *mDialog = nullptr;
 };
 
-bool QgsVectorLayer::countSymbolFeatures( bool showProgress )
+bool QgsVectorLayer::countSymbolFeatures()
 {
   if ( mSymbolFeatureCounted )
     return true;
@@ -697,103 +700,16 @@ bool QgsVectorLayer::countSymbolFeatures( bool showProgress )
     return false;
   }
 
-  QgsLegendSymbolList symbolList = mRenderer->legendSymbolItems();
-  QgsLegendSymbolList::const_iterator symbolIt = symbolList.constBegin();
-
-  for ( ; symbolIt != symbolList.constEnd(); ++symbolIt )
+  if ( !mFeatureCounter )
   {
-    mSymbolFeatureCountMap.insert( symbolIt->first, 0 );
-  }
+    mFeatureCounter.reset( new QgsVectorLayerFeatureCounter( this ) );
+    connect( mFeatureCounter.get(), &QgsVectorLayerFeatureCounter::symbolsCounted, this, &QgsVectorLayer::onSymbolsCounted );
+    connect( mFeatureCounter.get(), &QgsTask::taskCompleted, [ = ]() { mFeatureCounter.reset(); } );
+    connect( mFeatureCounter.get(), &QgsTask::taskTerminated, [ = ]() { mFeatureCounter.reset(); } );
 
-  long nFeatures = featureCount();
-
-  QWidget *mainWindow = nullptr;
-  Q_FOREACH ( QWidget *widget, qApp->topLevelWidgets() )
-  {
-    if ( widget->objectName() == QLatin1String( "QgisApp" ) )
-    {
-      mainWindow = widget;
-      break;
-    }
-  }
-
-  QProgressDialog progressDialog( tr( "Updating feature count for layer %1" ).arg( name() ), tr( "Abort" ), 0, nFeatures, mainWindow );
-  progressDialog.setWindowTitle( tr( "QGIS" ) );
-  progressDialog.setWindowModality( Qt::WindowModal );
-  if ( showProgress )
-  {
-    // Properly initialize to 0 as recommended in doc so that the evaluation
-    // of the total time properly works
-    progressDialog.setValue( 0 );
+    QgsApplication::taskManager()->addTask( mFeatureCounter.get() );
   }
-  int featuresCounted = 0;
-
-  // Renderer (rule based) may depend on context scale, with scale is ignored if 0
-  QgsRenderContext renderContext;
-  renderContext.setRendererScale( 0 );
-  renderContext.expressionContext().appendScopes( QgsExpressionContextUtils::globalProjectLayerScopes( this ) );
-
-  QgsFeatureRequest request;
-  if ( !mRenderer->filterNeedsGeometry() )
-    request.setFlags( QgsFeatureRequest::NoGeometry );
-  request.setSubsetOfAttributes( mRenderer->usedAttributes( renderContext ), mFields );
-  QgsFeatureIterator fit = getFeatures( request );
-  QgsVectorLayerInterruptionCheckerDuringCountSymbolFeatures interruptionCheck( &progressDialog );
-  if ( showProgress )
-  {
-    fit.setInterruptionChecker( &interruptionCheck );
-  }
-
-  mRenderer->startRender( renderContext, fields() );
-
-  QgsFeature f;
-  QTime time;
-  time.start();
-  while ( fit.nextFeature( f ) )
-  {
-    renderContext.expressionContext().setFeature( f );
-    QSet<QString> featureKeyList = mRenderer->legendKeysForFeature( f, renderContext );
-    Q_FOREACH ( const QString &key, featureKeyList )
-    {
-      mSymbolFeatureCountMap[key] += 1;
-    }
-    ++featuresCounted;
 
-    if ( showProgress )
-    {
-      // Refresh progress every 50 features or second
-      if ( ( featuresCounted % 50 == 0 ) || time.elapsed() > 1000 )
-      {
-        time.restart();
-        if ( featuresCounted > nFeatures ) //sometimes the feature count is not correct
-        {
-          progressDialog.setMaximum( 0 );
-        }
-        progressDialog.setValue( featuresCounted );
-      }
-      // So that we get a chance of hitting the Abort button
-#ifdef Q_OS_LINUX
-      // For some reason on Windows hasPendingEvents() always return true,
-      // but one iteration is actually enough on Windows to get good interactivity
-      // whereas on Linux we must allow for far more iterations.
-      // For safety limit the number of iterations
-      int nIters = 0;
-      while ( QCoreApplication::hasPendingEvents() && ++nIters < 100 )
-#endif
-      {
-        QCoreApplication::processEvents();
-      }
-      if ( progressDialog.wasCanceled() )
-      {
-        mSymbolFeatureCountMap.clear();
-        mRenderer->stopRender( renderContext );
-        return false;
-      }
-    }
-  }
-  mRenderer->stopRender( renderContext );
-  progressDialog.setValue( nFeatures );
-  mSymbolFeatureCounted = true;
   return true;
 }
 
@@ -3983,6 +3899,13 @@ void QgsVectorLayer::onRelationsLoaded()
   mEditFormConfig.onRelationsLoaded();
 }
 
+void QgsVectorLayer::onSymbolsCounted( const QHash<QString, long> &symbolFeatureCountMap )
+{
+  mSymbolFeatureCountMap = symbolFeatureCountMap;
+  mSymbolFeatureCounted = true;
+  emit symbolFeatureCountMapChanged();
+}
+
 QList<QgsRelation> QgsVectorLayer::referencingRelations( int idx ) const
 {
   return QgsProject::instance()->relationManager()->referencingRelations( this, idx );

src/core/qgsvectorlayer.h

@@ -65,6 +65,7 @@ class QgsSymbol;
 class QgsVectorLayerJoinInfo;
 class QgsVectorLayerEditBuffer;
 class QgsVectorLayerJoinBuffer;
+class QgsVectorLayerFeatureCounter;
 class QgsAbstractVectorLayerLabeling;
 class QgsPointV2;
 class QgsFeedback;
@@ -810,7 +811,7 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
      * \param showProgress show progress dialog
      * \returns true if calculated, false if failed or was canceled by user
      */
-    bool countSymbolFeatures( bool showProgress = true );
+    bool countSymbolFeatures();
 
     /**
      * Set the string (typically sql) used to define a subset of the layer
@@ -1846,11 +1847,18 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
      */
     void readOnlyChanged();
 
+    /**
+     * Emitted when the feature count for symbols on this layer has been recalculated.
+     *
+     * \since QGIS 3.0
+     */
+    void symbolFeatureCountMapChanged();
 
   private slots:
     void onJoinedFieldsChanged();
     void onFeatureDeleted( QgsFeatureId fid );
     void onRelationsLoaded();
+    void onSymbolsCounted( const QHash<QString, long> &symbolFeatureCountMap );
 
   protected:
     //! Set the extent
@@ -1883,7 +1891,6 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
 #endif
 
   private:                       // Private attributes
-
     QgsConditionalLayerStyles *mConditionalStyles = nullptr;
 
     //! Pointer to data provider derived from the abastract base class QgsDataProvider
@@ -2001,6 +2008,8 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
 
     mutable QMutex mFeatureSourceConstructorMutex;
 
+    std::unique_ptr<QgsVectorLayerFeatureCounter> mFeatureCounter;
+
     friend class QgsVectorLayerFeatureSource;
 };
 

src/core/qgsvectorlayerfeaturecounter.cpp

@@ -0,0 +1,69 @@
+#include "qgsvectorlayerfeaturecounter.h"
+
+QgsVectorLayerFeatureCounter::QgsVectorLayerFeatureCounter( QgsVectorLayer *layer )
+  : mSource( new QgsVectorLayerFeatureSource( layer ) )
+  , mRenderer( layer->renderer()->clone() )
+  , mExpressionContextScopes( QgsExpressionContextUtils::globalProjectLayerScopes( layer ) )
+  , mFeatureCount( layer->featureCount() )
+{
+}
+
+bool QgsVectorLayerFeatureCounter::run()
+{
+  QgsLegendSymbolList symbolList = mRenderer->legendSymbolItems();
+  QgsLegendSymbolList::const_iterator symbolIt = symbolList.constBegin();
+
+  for ( ; symbolIt != symbolList.constEnd(); ++symbolIt )
+  {
+    mSymbolFeatureCountMap.insert( symbolIt->first, 0 );
+  }
+
+  int featuresCounted = 0;
+
+  // Renderer (rule based) may depend on context scale, with scale is ignored if 0
+  QgsRenderContext renderContext;
+  renderContext.setRendererScale( 0 );
+  renderContext.expressionContext().appendScopes( mExpressionContextScopes );
+
+  QgsFeatureRequest request;
+  if ( !mRenderer->filterNeedsGeometry() )
+    request.setFlags( QgsFeatureRequest::NoGeometry );
+  request.setSubsetOfAttributes( mRenderer->usedAttributes( renderContext ), mSource->fields() );
+  QgsFeatureIterator fit = mSource->getFeatures( request );
+
+  // TODO: replace QgsInterruptionChecker with QgsFeedback
+  // fit.setInterruptionChecker( mFeedback );
+
+  mRenderer->startRender( renderContext, mSource->fields() );
+
+  double progress = 0;
+  QgsFeature f;
+  while ( fit.nextFeature( f ) )
+  {
+    renderContext.expressionContext().setFeature( f );
+    QSet<QString> featureKeyList = mRenderer->legendKeysForFeature( f, renderContext );
+    Q_FOREACH ( const QString &key, featureKeyList )
+    {
+      mSymbolFeatureCountMap[key] += 1;
+    }
+    ++featuresCounted;
+
+    double p = ( featuresCounted / mFeatureCount ) * 100;
+    if ( p - progress > 1 )
+    {
+      progress = p;
+      setProgress( progress );
+    }
+
+    if ( isCanceled() )
+    {
+      mRenderer->stopRender( renderContext );
+      return false;
+    }
+  }
+  mRenderer->stopRender( renderContext );
+  setProgress( 100 );
+
+  emit symbolsCounted( mSymbolFeatureCountMap );
+  return true;
+}