From 2fb85192aad7ff5757b50d545a8d6119434a0483 Mon Sep 17 00:00:00 2001
From: Nyall Dawson <nyall.dawson@gmail.com>
Date: Mon, 22 Jul 2024 10:52:31 +1000
Subject: [PATCH] Fix crash when extracting symbols from project with layout
 legend

Legend must be initialized before calling style visitor function

Fixes #57609
---
 .../layout/qgslayoutitemlegend.sip.in             |  1 +
 .../layout/qgslayoutitemlegend.sip.in             |  1 +
 src/core/layout/qgslayoutitemlegend.cpp           | 15 +++++++++++----
 src/core/layout/qgslayoutitemlegend.h             |  9 ++++++++-
 4 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/python/PyQt6/core/auto_generated/layout/qgslayoutitemlegend.sip.in b/python/PyQt6/core/auto_generated/layout/qgslayoutitemlegend.sip.in
index fd646b104aed..6d45578e3c7f 100644
--- a/python/PyQt6/core/auto_generated/layout/qgslayoutitemlegend.sip.in
+++ b/python/PyQt6/core/auto_generated/layout/qgslayoutitemlegend.sip.in
@@ -122,6 +122,7 @@ Returns whether the legend should automatically resize to fit its contents.
 Returns the legend model.
 %End
 
+
     void setAutoUpdateModel( bool autoUpdate );
 %Docstring
 Sets whether the legend content should auto update to reflect changes in the project's
diff --git a/python/core/auto_generated/layout/qgslayoutitemlegend.sip.in b/python/core/auto_generated/layout/qgslayoutitemlegend.sip.in
index fd646b104aed..6d45578e3c7f 100644
--- a/python/core/auto_generated/layout/qgslayoutitemlegend.sip.in
+++ b/python/core/auto_generated/layout/qgslayoutitemlegend.sip.in
@@ -122,6 +122,7 @@ Returns whether the legend should automatically resize to fit its contents.
 Returns the legend model.
 %End
 
+
     void setAutoUpdateModel( bool autoUpdate );
 %Docstring
 Sets whether the legend content should auto update to reflect changes in the project's
diff --git a/src/core/layout/qgslayoutitemlegend.cpp b/src/core/layout/qgslayoutitemlegend.cpp
index cf14e3789d8e..b14e9c7665d1 100644
--- a/src/core/layout/qgslayoutitemlegend.cpp
+++ b/src/core/layout/qgslayoutitemlegend.cpp
@@ -319,12 +319,13 @@ void QgsLayoutItemLegend::setCustomLayerTree( QgsLayerTree *rootGroup )
   mCustomLayerTree.reset( rootGroup );
 }
 
-void QgsLayoutItemLegend::ensureModelIsInitialized()
+void QgsLayoutItemLegend::ensureModelIsInitialized() const
 {
   if ( mDeferLegendModelInitialization )
   {
-    mDeferLegendModelInitialization = false;
-    setCustomLayerTree( mCustomLayerTree.release() );
+    QgsLayoutItemLegend *mutableThis = const_cast< QgsLayoutItemLegend * >( this );
+    mutableThis->mDeferLegendModelInitialization = false;
+    mutableThis->setCustomLayerTree( mutableThis->mCustomLayerTree.release() );
   }
 }
 
@@ -334,6 +335,12 @@ QgsLegendModel *QgsLayoutItemLegend::model()
   return mLegendModel.get();
 }
 
+const QgsLegendModel *QgsLayoutItemLegend::model() const
+{
+  ensureModelIsInitialized();
+  return mLegendModel.get();
+}
+
 void QgsLayoutItemLegend::setAutoUpdateModel( bool autoUpdate )
 {
   if ( autoUpdate == autoUpdateModel() )
@@ -1345,7 +1352,7 @@ bool QgsLayoutItemLegend::accept( QgsStyleEntityVisitorInterface *visitor ) cons
     }
     return true;
   };
-  return visit( mLegendModel->rootGroup( ) );
+  return visit( model()->rootGroup( ) );
 }
 
 bool QgsLayoutItemLegend::isRefreshing() const
diff --git a/src/core/layout/qgslayoutitemlegend.h b/src/core/layout/qgslayoutitemlegend.h
index 0302c18141a7..8c4b8e31fbeb 100644
--- a/src/core/layout/qgslayoutitemlegend.h
+++ b/src/core/layout/qgslayoutitemlegend.h
@@ -158,6 +158,13 @@ class CORE_EXPORT QgsLayoutItemLegend : public QgsLayoutItem
      */
     QgsLegendModel *model();
 
+    /**
+     * Returns the legend model.
+     *
+     * \note Not available in Python bindings
+     */
+    const QgsLegendModel *model() const SIP_SKIP;
+
     /**
      * Sets whether the legend content should auto update to reflect changes in the project's
      * layer tree.
@@ -634,7 +641,7 @@ class CORE_EXPORT QgsLayoutItemLegend : public QgsLayoutItem
 
     void setModelStyleOverrides( const QMap<QString, QString> &overrides );
 
-    void ensureModelIsInitialized();
+    void ensureModelIsInitialized() const;
     std::unique_ptr< QgsLegendModel > mLegendModel;
     std::unique_ptr< QgsLayerTree > mCustomLayerTree;
     bool mDeferLegendModelInitialization = true;