Add API to "expand" out group layer children when querying QgsMapSett…

…ings for layers There's two reasons why someone would be calling this method: - to determine which layers should be rendered by a render job - to determine which layers are actually visible in the map Depending on which is required, we either want to expand out groups and remove the group layer itself from the list (or not)
qgis · Nov 23, 2021 · a5b9c7b · a5b9c7b
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diff --git a/python/core/auto_generated/qgsmapsettings.sip.in b/python/core/auto_generated/qgsmapsettings.sip.in
@@ -234,23 +234,29 @@ Returns the magnification factor.
 .. versionadded:: 2.16
 %End
 
-    QStringList layerIds() const;
+    QStringList layerIds( bool expandGroupLayers = false ) const;
 %Docstring
 Returns the list of layer IDs which will be rendered in the map.
 
 The layers are stored in the reverse order of how they are rendered (layer with index 0 will be on top).
 
+Since QGIS 3.24, if the ``expandGroupLayers`` option is ``True`` then group layers will be converted to
+all their child layers.
+
 .. seealso:: :py:func:`layers`
 
 .. seealso:: :py:func:`setLayers`
 %End
 
-    QList<QgsMapLayer *> layers() const;
+    QList<QgsMapLayer *> layers( bool expandGroupLayers = false ) const;
 %Docstring
 Returns the list of layers which will be rendered in the map.
 
 The layers are stored in the reverse order of how they are rendered (layer with index 0 will be on top)
 
+Since QGIS 3.24, if the ``expandGroupLayers`` option is ``True`` then group layers will be converted to
+all their child layers.
+
 .. seealso:: :py:func:`setLayers`
 
 .. seealso:: :py:func:`layerIds`

diff --git a/src/core/qgsmapsettings.cpp b/src/core/qgsmapsettings.cpp
@@ -27,6 +27,7 @@
 #include "qgsxmlutils.h"
 #include "qgsexception.h"
 #include "qgsgeometry.h"
+#include "qgsgrouplayer.h"
 
 Q_GUI_EXPORT extern int qt_defaultDpiX();
 
@@ -285,15 +286,42 @@ void QgsMapSettings::setDpiTarget( double dpi )
   mDpiTarget = dpi;
 }
 
-QStringList QgsMapSettings::layerIds() const
+QStringList QgsMapSettings::layerIds( bool expandGroupLayers ) const
 {
-  return _qgis_listQPointerToIDs( mLayers );
+  const QList<QgsMapLayer * > mapLayers = layers( expandGroupLayers );
+  QStringList res;
+  res.reserve( mapLayers.size() );
+  for ( const QgsMapLayer *layer : mapLayers )
+    res << layer->id();
+  return res;
 }
 
-
-QList<QgsMapLayer *> QgsMapSettings::layers() const
+QList<QgsMapLayer *> QgsMapSettings::layers( bool expandGroupLayers ) const
 {
-  return _qgis_listQPointerToRaw( mLayers );
+  const QList<QgsMapLayer *> actualLayers = _qgis_listQPointerToRaw( mLayers );
+  if ( !expandGroupLayers )
+    return actualLayers;
+
+  QList< QgsMapLayer * > result;
+
+  std::function< void( const QList< QgsMapLayer * >& layers ) > expandLayers;
+  expandLayers = [&result, &expandLayers]( const QList< QgsMapLayer * > &layers )
+  {
+    for ( QgsMapLayer *layer : layers )
+    {
+      if ( QgsGroupLayer *groupLayer = qobject_cast< QgsGroupLayer * >( layer ) )
+      {
+        expandLayers( groupLayer->childLayers() );
+      }
+      else
+      {
+        result << layer;
+      }
+    }
+  };
+
+  expandLayers( actualLayers );
+  return result;
 }
 
 void QgsMapSettings::setLayers( const QList<QgsMapLayer *> &layers )

diff --git a/src/core/qgsmapsettings.h b/src/core/qgsmapsettings.h
@@ -244,20 +244,26 @@ class CORE_EXPORT QgsMapSettings : public QgsTemporalRangeObject
      *
      * The layers are stored in the reverse order of how they are rendered (layer with index 0 will be on top).
      *
+     * Since QGIS 3.24, if the \a expandGroupLayers option is TRUE then group layers will be converted to
+     * all their child layers.
+     *
      * \see layers()
      * \see setLayers()
      */
-    QStringList layerIds() const;
+    QStringList layerIds( bool expandGroupLayers = false ) const;
 
     /**
      * Returns the list of layers which will be rendered in the map.
      *
      * The layers are stored in the reverse order of how they are rendered (layer with index 0 will be on top)
      *
+     * Since QGIS 3.24, if the \a expandGroupLayers option is TRUE then group layers will be converted to
+     * all their child layers.
+     *
      * \see setLayers()
      * \see layerIds()
      */
-    QList<QgsMapLayer *> layers() const;
+    QList<QgsMapLayer *> layers( bool expandGroupLayers = false ) const;
 
     /**
      * Sets the list of \a layers to render in the map.

diff --git a/tests/src/core/testqgsmapsettings.cpp b/tests/src/core/testqgsmapsettings.cpp
@@ -31,6 +31,7 @@
 #include "qgsexpressioncontextutils.h"
 #include "qgsrenderedfeaturehandlerinterface.h"
 #include "qgsrendercontext.h"
+#include "qgsgrouplayer.h"
 
 class TestHandler : public QgsRenderedFeatureHandlerInterface
 {
@@ -66,6 +67,7 @@ class TestQgsMapSettings: public QObject
     void testClippingRegions();
     void testComputeExtentForScale();
     void testComputeScaleForExtent();
+    void testLayersWithGroupLayers();
 
   private:
     QString toString( const QPolygonF &p, int decimalPlaces = 2 ) const;
@@ -685,5 +687,40 @@ void TestQgsMapSettings::testComputeScaleForExtent()
   QGSCOMPARENEAR( scale, testScale, 0.001 );
 }
 
+void TestQgsMapSettings::testLayersWithGroupLayers()
+{
+  // test retrieving layers from map settings when a QgsGroupLayer is present
+  QgsMapSettings settings;
+
+  std::unique_ptr< QgsVectorLayer > vlA = std::make_unique< QgsVectorLayer >( QStringLiteral( "Point" ), QStringLiteral( "a" ), QStringLiteral( "memory" ) );
+  std::unique_ptr< QgsVectorLayer > vlB = std::make_unique< QgsVectorLayer >( QStringLiteral( "Point" ), QStringLiteral( "b" ), QStringLiteral( "memory" ) );
+  std::unique_ptr< QgsVectorLayer > vlC = std::make_unique< QgsVectorLayer >( QStringLiteral( "Point" ), QStringLiteral( "c" ), QStringLiteral( "memory" ) );
+
+  QgsGroupLayer::LayerOptions options( ( QgsCoordinateTransformContext() ) );
+  QgsGroupLayer groupLayer( QStringLiteral( "group" ), options );
+  groupLayer.setChildLayers( { vlB.get(), vlC.get() } );
+  settings.setLayers( { vlA.get(), &groupLayer } );
+
+  // without expanding groups
+  QCOMPARE( settings.layers().size(), 2 );
+  QCOMPARE( settings.layers().at( 0 ), vlA.get() );
+  QCOMPARE( settings.layers().at( 1 ), &groupLayer );
+
+  QCOMPARE( settings.layerIds().size(), 2 );
+  QCOMPARE( settings.layerIds().at( 0 ), vlA->id() );
+  QCOMPARE( settings.layerIds().at( 1 ), groupLayer.id() );
+
+  // with expanding groups
+  QCOMPARE( settings.layers( true ).size(), 3 );
+  QCOMPARE( settings.layers( true ).at( 0 ), vlA.get() );
+  QCOMPARE( settings.layers( true ).at( 1 ), vlB.get() );
+  QCOMPARE( settings.layers( true ).at( 2 ), vlC.get() );
+
+  QCOMPARE( settings.layerIds( true ).size(), 3 );
+  QCOMPARE( settings.layerIds( true ).at( 0 ), vlA->id() );
+  QCOMPARE( settings.layerIds( true ).at( 1 ), vlB->id() );
+  QCOMPARE( settings.layerIds( true ).at( 2 ), vlC->id() );
+}
+
 QGSTEST_MAIN( TestQgsMapSettings )
 #include "testqgsmapsettings.moc"