Allow cancellation of PAL labeling computation

src/core/pal/pal.cpp

@@ -85,6 +85,9 @@ namespace pal
     // do not init and exit GEOS - we do it inside QGIS
     //initGEOS( geosNotice, geosError );
 
+    fnIsCancelled = 0;
+    fnIsCancelledContext = 0;
+
     layers = new QList<Layer*>();
 
     lyrsMutex = new SimpleMutex();
@@ -316,6 +319,9 @@ namespace pal
     double scale = (( FilterContext* ) ctx )->scale;
     Pal* pal = (( FilterContext* )ctx )->pal;
 
+    if ( pal->isCancelled() )
+      return false; // do not continue searching
+
     double amin[2], amax[2];
     pset->getBoundingBox( amin, amax );
 
@@ -509,6 +515,13 @@ namespace pal
     filterCtx.pal = this;
     obstacles->Search( amin, amax, filteringCallback, ( void* ) &filterCtx );
 
+    if ( isCancelled() )
+    {
+      delete fFeats;
+      delete prob;
+      delete obstacles;
+      return 0;
+    }
 
     int idlp = 0;
     for ( i = 0; i < prob->nbft; i++ ) /* foreach feature into prob */
@@ -580,6 +593,14 @@ namespace pal
     j = 0;
     while ( fFeats->size() > 0 ) // foreach feature
     {
+      if ( isCancelled() )
+      {
+        delete fFeats;
+        delete prob;
+        delete obstacles;
+        return 0;
+      }
+
       feat = fFeats->pop_front();
       for ( i = 0; i < feat->nblp; i++, idlp++ )  // foreach label candidate
       {
@@ -798,6 +819,12 @@ namespace pal
     return solution;
   }
 
+  void Pal::registerCancellationCallback(Pal::FnIsCancelled fnCancelled, void *context)
+  {
+    fnIsCancelled = fnCancelled;
+    fnIsCancelledContext = context;
+  }
+
   Problem* Pal::extractProblem( double scale, double bbox[4] )
   {
     // find out: nbLayers, layersName, layersFactor

src/core/pal/pal.h

@@ -172,6 +172,13 @@ namespace pal
        */
       bool showPartial;
 
+
+      typedef bool (*FnIsCancelled)(void* ctx);
+      /** Callback that may be called from PAL to check whether the job has not been cancelled in meanwhile */
+      FnIsCancelled fnIsCancelled;
+      /** Application-specific context for the cancellation check function */
+      void* fnIsCancelledContext;
+
       /**
        * \brief Problem factory
        * Extract features to label and generates candidates for them,
@@ -339,6 +346,11 @@ namespace pal
                                            PalStat **stat,
                                            bool displayAll );
 
+      /** Register a function that returns whether this job has been cancelled - PAL calls it during the computation */
+      void registerCancellationCallback( FnIsCancelled fnCancelled, void* context );
+
+      /** Check whether the job has been cancelled */
+      inline bool isCancelled() { return fnIsCancelled ? fnIsCancelled( fnIsCancelledContext ) : false; }
 
       Problem* extractProblem( double scale, double bbox[4] );
 

src/core/pal/problem.cpp

@@ -349,6 +349,13 @@ namespace pal
 
     while ( list->getSize() > 0 ) // O (log size)
     {
+      if ( pal->isCancelled() )
+      {
+        delete context;
+        delete list;
+        return;
+      }
+
       label = list->getBest();   // O (log size)
 
 

src/core/qgspallabeling.cpp

@@ -3818,12 +3818,21 @@ void QgsPalLabeling::dataDefinedDropShadow( QgsPalLayerSettings& tmpLyr,
   }
 }
 
+
+// helper function for checking for job cancellation within PAL
+static bool _palIsCancelled( void* ctx )
+{
+  return ( ( QgsRenderContext* ) ctx )->renderingStopped();
+}
+
 void QgsPalLabeling::drawLabeling( QgsRenderContext& context )
 {
   Q_ASSERT( mMapSettings != NULL );
   QPainter* painter = context.painter();
   QgsRectangle extent = context.extent();
 
+  mPal->registerCancellationCallback( &_palIsCancelled, &context );
+
   delete mResults;
   mResults = new QgsLabelingResults;
 
@@ -3849,6 +3858,9 @@ void QgsPalLabeling::drawLabeling( QgsRenderContext& context )
     return;
   }
 
+  if ( context.renderingStopped() )
+    return; // it has been cancelled
+
   const QgsMapToPixel& xform = mMapSettings->mapToPixel();
 
   // draw rectangles with all candidates
@@ -3876,12 +3888,23 @@ void QgsPalLabeling::drawLabeling( QgsRenderContext& context )
   QgsDebugMsgLevel( QString( "LABELING work:  %1 ms ... labels# %2" ).arg( t.elapsed() ).arg( labels->size() ), 4 );
   t.restart();
 
+  if ( context.renderingStopped() )
+  {
+    delete problem;
+    delete labels;
+    deleteTemporaryData();
+    return;
+  }
+
   painter->setRenderHint( QPainter::Antialiasing );
 
   // draw the labels
   std::list<LabelPosition*>::iterator it = labels->begin();
   for ( ; it != labels->end(); ++it )
   {
+    if ( context.renderingStopped() )
+      break;
+
     QgsPalGeometry* palGeometry = dynamic_cast< QgsPalGeometry* >(( *it )->getFeaturePart()->getUserGeometry() );
     if ( !palGeometry )
     {
@@ -3996,7 +4019,11 @@ void QgsPalLabeling::drawLabeling( QgsRenderContext& context )
 
   delete problem;
   delete labels;
+  deleteTemporaryData();
+}
 
+void QgsPalLabeling::deleteTemporaryData()
+{
   // delete all allocated geometries for features
   QHash<QgsVectorLayer*, QgsPalLayerSettings>::iterator lit;
   for ( lit = mActiveLayers.begin(); lit != mActiveLayers.end(); ++lit )

src/core/qgspallabeling.h

@@ -813,6 +813,8 @@ class CORE_EXPORT QgsPalLabeling : public QgsLabelingEngineInterface
     void dataDefinedDropShadow( QgsPalLayerSettings& tmpLyr,
                                 const QMap< QgsPalLayerSettings::DataDefinedProperties, QVariant >& ddValues );
 
+    void deleteTemporaryData();
+
     // hashtable of layer settings, being filled during labeling
     QHash<QgsVectorLayer*, QgsPalLayerSettings> mActiveLayers;
     // hashtable of active diagram layers