Don't show private layers in print layout legends by default

When a print layout legend is in auto mode, private layers should
not be included

Fixes #51427

src/core/layout/qgslayoutitemlegend.cpp

@@ -22,6 +22,7 @@
 #include "qgslayoutmodel.h"
 #include "qgslayertree.h"
 #include "qgslayertreemodel.h"
+#include "qgslayertreefilterproxymodel.h"
 #include "qgslegendrenderer.h"
 #include "qgslegendstyle.h"
 #include "qgslogger.h"
@@ -153,7 +154,7 @@ void QgsLayoutItemLegend::paint( QPainter *painter, const QStyleOptionGraphicsIt
   }
   mInitialMapScaleCalculated = true;
 
-  QgsLegendRenderer legendRenderer( mLegendModel.get(), mSettings );
+  QgsLegendRenderer legendRenderer = createRenderer();
   legendRenderer.setLegendSize( mForceResize && mSizeToContents ? QSize() : rect().size() );
 
   const QPointF oldPos = pos();
@@ -265,7 +266,7 @@ void QgsLayoutItemLegend::draw( QgsLayoutItemRenderContext &context )
     Q_NOWARN_DEPRECATED_POP
   }
 
-  QgsLegendRenderer legendRenderer( mLegendModel.get(), mSettings );
+  QgsLegendRenderer legendRenderer = createRenderer();
   legendRenderer.setLegendSize( rect().size() );
 
   legendRenderer.drawLegend( rc );
@@ -288,7 +289,7 @@ void QgsLayoutItemLegend::adjustBoxSize()
   QgsRenderContext context = mMap ? QgsLayoutUtils::createRenderContextForMap( mMap, nullptr ) :
                              QgsLayoutUtils::createRenderContextForLayout( mLayout, nullptr );
 
-  QgsLegendRenderer legendRenderer( mLegendModel.get(), mSettings );
+  QgsLegendRenderer legendRenderer = createRenderer();
   const QSizeF size = legendRenderer.minimumSize( &context );
   QgsDebugMsgLevel( QStringLiteral( "width = %1 height = %2" ).arg( size.width() ).arg( size.height() ), 2 );
   if ( size.isValid() )
@@ -329,6 +330,16 @@ void QgsLayoutItemLegend::ensureModelIsInitialized() const
   }
 }
 
+QgsLegendRenderer QgsLayoutItemLegend::createRenderer() const
+{
+  QgsLegendRenderer res( mLegendModel.get(), mSettings );
+
+  // only show private layers when not in auto update mode
+  res.proxyModel()->setShowPrivateLayers( static_cast< bool >( mCustomLayerTree ) );
+
+  return res;
+}
+
 QgsLegendModel *QgsLayoutItemLegend::model()
 {
   ensureModelIsInitialized();

src/core/layout/qgslayoutitemlegend.h

@@ -351,7 +351,7 @@ class CORE_EXPORT QgsLayoutItemLegend : public QgsLayoutItem
      * A symbol size of 0.0 indicates no maximum is set.
      *
      * \see maximumSymbolSize()
-     * \since QGIS 3.16
+     * \since QGIS 3.16:
      */
     void setMaximumSymbolSize( double size );
 
@@ -642,6 +642,9 @@ class CORE_EXPORT QgsLayoutItemLegend : public QgsLayoutItem
     void setModelStyleOverrides( const QMap<QString, QString> &overrides );
 
     void ensureModelIsInitialized() const;
+
+    QgsLegendRenderer createRenderer() const;
+
     std::unique_ptr< QgsLegendModel > mLegendModel;
     std::unique_ptr< QgsLayerTree > mCustomLayerTree;
     bool mDeferLegendModelInitialization = true;

src/core/qgslegendrenderer.cpp

@@ -37,6 +37,15 @@ QgsLegendRenderer::QgsLegendRenderer( QgsLayerTreeModel *legendModel, const QgsL
   mProxyModel->setLayerTreeModel( mLegendModel );
 }
 
+QgsLegendRenderer::QgsLegendRenderer( QgsLegendRenderer &&other )
+  : mLegendModel( other.mLegendModel )
+  , mProxyModel( std::move( other.mProxyModel ) )
+  , mSettings( std::move( other.mSettings ) )
+  , mLegendSize( other.mLegendSize )
+{
+  mProxyModel->setLayerTreeModel( mLegendModel );
+}
+
 QgsLegendRenderer::~QgsLegendRenderer() = default;
 
 QSizeF QgsLegendRenderer::minimumSize( QgsRenderContext *renderContext )

src/core/qgslegendrenderer.h

@@ -58,6 +58,7 @@ class CORE_EXPORT QgsLegendRenderer
 #ifndef SIP_RUN
     QgsLegendRenderer( const QgsLegendRenderer &other ) = delete;
     QgsLegendRenderer &operator=( const QgsLegendRenderer &other ) = delete;
+    QgsLegendRenderer( QgsLegendRenderer &&other );
 #endif
 
     /**

tests/src/python/test_qgslayoutlegend.py

@@ -24,6 +24,7 @@ from qgis.PyQt.QtGui import (
 from qgis.PyQt.QtXml import QDomDocument
 
 from qgis.core import (
+    QgsMapLayer,
     QgsCategorizedSymbolRenderer,
     QgsCoordinateReferenceSystem,
     QgsExpression,
@@ -441,6 +442,49 @@ class TestQgsLayoutItemLegend(QgisTestCase, LayoutItemTestCase):
             )
         )
 
+    def test_private_layers(self):
+        """
+        Test legend does not contain private layers by default
+        """
+        point_path = os.path.join(TEST_DATA_DIR, 'points.shp')
+        point_layer1 = QgsVectorLayer(point_path, 'points 1', 'ogr')
+        point_layer2 = QgsVectorLayer(point_path, 'points 2', 'ogr')
+        point_layer2.setFlags(QgsMapLayer.LayerFlag.Private)
+        p = QgsProject()
+        p.addMapLayers([point_layer1, point_layer2])
+
+        marker_symbol = QgsMarkerSymbol.createSimple(
+            {'color': '#ff0000', 'outline_style': 'no', 'size': '5', 'size_unit': 'MapUnit'})
+
+        point_layer1.setRenderer(
+            QgsSingleSymbolRenderer(marker_symbol.clone()))
+        point_layer2.setRenderer(
+            QgsSingleSymbolRenderer(marker_symbol.clone()))
+
+        layout = QgsLayout(p)
+        layout.initializeDefaults()
+
+        legend = QgsLayoutItemLegend(layout)
+        legend.setTitle("Legend")
+        legend.attemptSetSceneRect(QRectF(120, 20, 80, 80))
+        legend.setFrameEnabled(True)
+        legend.setFrameStrokeWidth(QgsLayoutMeasurement(2))
+        legend.setBackgroundColor(QColor(200, 200, 200))
+        legend.setTitle('')
+        layout.addLayoutItem(legend)
+
+        legend.setStyleFont(QgsLegendStyle.Style.Title, QgsFontUtils.getStandardTestFont('Bold', 16))
+        legend.setStyleFont(QgsLegendStyle.Style.Group, QgsFontUtils.getStandardTestFont('Bold', 16))
+        legend.setStyleFont(QgsLegendStyle.Style.Subgroup, QgsFontUtils.getStandardTestFont('Bold', 16))
+        legend.setStyleFont(QgsLegendStyle.Style.Symbol, QgsFontUtils.getStandardTestFont('Bold', 16))
+        legend.setStyleFont(QgsLegendStyle.Style.SymbolLabel, QgsFontUtils.getStandardTestFont('Bold', 16))
+
+        self.assertTrue(
+            self.render_layout_check(
+                'composer_legend_private_layers', layout
+            )
+        )
+
     def testResizeDisabled(self):
         """
         Test that test legend does not resize if auto size is disabled