Add method to determine layers participating in a label engine

nyalldawson · nyalldawson · commit 1e5a93b0f993 · 2017-02-01T12:09:08.000+10:00
diff --git a/src/core/qgslabelingengine.cpp b/src/core/qgslabelingengine.cpp
@@ -88,6 +88,22 @@ QgsLabelingEngine::~QgsLabelingEngine()
   qDeleteAll( mSubProviders );
 }
 
+QStringList QgsLabelingEngine::participatingLayerIds() const
+{
+  QSet< QString > ids;
+  Q_FOREACH ( QgsAbstractLabelProvider* provider, mProviders )
+  {
+    if ( !provider->layerId().isEmpty() )
+      ids << provider->layerId();
+  }
+  Q_FOREACH ( QgsAbstractLabelProvider* provider, mSubProviders )
+  {
+    if ( !provider->layerId().isEmpty() )
+      ids << provider->layerId();
+  }
+  return ids.toList();
+}
+
 void QgsLabelingEngine::addProvider( QgsAbstractLabelProvider* provider )
 {
   provider->setEngine( this );
diff --git a/src/core/qgslabelingengine.h b/src/core/qgslabelingengine.h
@@ -186,6 +186,12 @@ class CORE_EXPORT QgsLabelingEngine
     //! Get associated map settings
     const QgsMapSettings& mapSettings() const { return mMapSettings; }
 
+    /**
+     * Returns a list of layer IDs for layers with providers in the engine.
+     * @note added in QGIS 3.0
+     */
+    QStringList participatingLayerIds() const;
+
     //! Add provider of label features. Takes ownership of the provider
     void addProvider( QgsAbstractLabelProvider* provider );
 
diff --git a/tests/src/core/testqgslabelingengine.cpp b/tests/src/core/testqgslabelingengine.cpp
@@ -45,6 +45,7 @@ class TestQgsLabelingEngine : public QObject
     void testEncodeDecodePositionOrder();
     void testSubstitutions();
     void testCapitalization();
+    void testParticipatingLayers();
 
   private:
     QgsVectorLayer* vl;
@@ -534,6 +535,35 @@ void TestQgsLabelingEngine::testCapitalization()
   QCOMPARE( provider4->mLabels.at( 0 )->labelText(), QString( "A TeSt LABEL" ) );
 }
 
+void TestQgsLabelingEngine::testParticipatingLayers()
+{
+  QgsLabelingEngine engine;
+  QVERIFY( engine.participatingLayerIds().isEmpty() );
+
+  QgsPalLayerSettings settings1;
+  QgsVectorLayerLabelProvider* provider = new QgsVectorLayerLabelProvider( vl, QStringLiteral( "test" ), true, &settings1 );
+  engine.addProvider( provider );
+  QCOMPARE( engine.participatingLayerIds(), QStringList() << vl->id() );
+
+  QgsVectorLayer* layer2 = new QgsVectorLayer( QStringLiteral( "Point?field=col1:integer" ), QStringLiteral( "layer2" ), QStringLiteral( "memory" ) );
+  QgsPalLayerSettings settings2;
+  QgsVectorLayerLabelProvider* provider2 = new QgsVectorLayerLabelProvider( layer2, QStringLiteral( "test2" ), true, &settings2 );
+  engine.addProvider( provider2 );
+  QCOMPARE( engine.participatingLayerIds().toSet(), QSet< QString >() << vl->id() << layer2->id() );
+
+  // add a rule-based labeling node
+  QgsRuleBasedLabeling::Rule* root = new QgsRuleBasedLabeling::Rule( 0 );
+  QgsPalLayerSettings s1;
+  root->appendChild( new QgsRuleBasedLabeling::Rule( new QgsPalLayerSettings( s1 ) ) );
+  QgsPalLayerSettings s2;
+  root->appendChild( new QgsRuleBasedLabeling::Rule( new QgsPalLayerSettings( s2 ) ) );
+
+  QgsVectorLayer* layer3 = new QgsVectorLayer( QStringLiteral( "Point?field=col1:integer" ), QStringLiteral( "layer3" ), QStringLiteral( "memory" ) );
+  QgsRuleBasedLabelProvider* ruleProvider = new QgsRuleBasedLabelProvider( QgsRuleBasedLabeling( root ), layer3 );
+  engine.addProvider( ruleProvider );
+  QCOMPARE( engine.participatingLayerIds().toSet(), QSet< QString >() << vl->id() << layer2->id() << layer3->id() );
+}
+
 bool TestQgsLabelingEngine::imageCheck( const QString& testName, QImage &image, int mismatchCount )
 {
   //draw background
