Cleanup handling of default label format for project, and avoid a QgsProject::instance() use in core

python/core/auto_generated/symbology/qgsstyle.sip.in

@@ -759,6 +759,13 @@ Returns the default patch geometry for the given symbol ``type`` and ``size`` as
 Returns the default text format to use for new text based objects in the specified ``context``.
 
 .. versionadded:: 3.20
+%End
+
+    static QgsTextFormat defaultTextFormatForProject( QgsProject *project,  QgsStyle::TextFormatContext context = QgsStyle::TextFormatContext::Labeling );
+%Docstring
+Returns the default text format to use for new text based objects for the specified ``project``, in the specified ``context``.
+
+.. versionadded:: 3.26
 %End
 
     bool saveSymbol3D( const QString &name, QgsAbstract3DSymbol *symbol /Transfer/, bool favorite, const QStringList &tags );

src/core/labeling/qgsvectorlayerlabeling.cpp

@@ -50,6 +50,7 @@ QgsPalLayerSettings QgsAbstractVectorLayerLabeling::defaultSettingsForLayer( con
 {
   QgsPalLayerSettings settings;
   settings.fieldName = layer->displayField();
+  settings.setFormat( QgsStyle::defaultTextFormatForProject( layer->project() ) );
 
   switch ( layer->geometryType() )
   {

src/core/symbology/qgsstyle.cpp

@@ -1211,13 +1211,21 @@ QList<QList<QPolygonF> > QgsStyle::defaultPatchAsQPolygonF( Qgis::SymbolType typ
 
 QgsTextFormat QgsStyle::defaultTextFormat( QgsStyle::TextFormatContext ) const
 {
-  QgsTextFormat defaultTextFormat = QgsProject::instance()->styleSettings()->defaultTextFormat();
+  return textFormat( QStringLiteral( "Default" ) );
-  if ( defaultTextFormat.isValid() )
+}
+
+QgsTextFormat QgsStyle::defaultTextFormatForProject( QgsProject *project, TextFormatContext context )
+{
+  if ( project )
   {
-    return defaultTextFormat;
+    QgsTextFormat defaultTextFormat = project->styleSettings()->defaultTextFormat();
+    if ( defaultTextFormat.isValid() )
+    {
+      return defaultTextFormat;
+    }
   }
 
-  return textFormat( QStringLiteral( "Default" ) );
+  return QgsStyle::defaultStyle()->defaultTextFormat( context );
 }
 
 bool QgsStyle::saveSymbol3D( const QString &name, QgsAbstract3DSymbol *symbol, bool favorite, const QStringList &tags )

src/core/symbology/qgsstyle.h

@@ -777,6 +777,13 @@ class CORE_EXPORT QgsStyle : public QObject
      */
     QgsTextFormat defaultTextFormat( QgsStyle::TextFormatContext context = QgsStyle::TextFormatContext::Labeling ) const;
 
+    /**
+     * Returns the default text format to use for new text based objects for the specified \a project, in the specified \a context.
+     *
+     * \since QGIS 3.26
+     */
+    static QgsTextFormat defaultTextFormatForProject( QgsProject *project,  QgsStyle::TextFormatContext context = QgsStyle::TextFormatContext::Labeling );
+
     /**
      * Adds a 3d \a symbol to the database.
      *

src/gui/annotations/qgscreateannotationitemmaptool_impl.cpp

@@ -99,7 +99,7 @@ void QgsCreatePointTextItemMapTool::cadCanvasPressEvent( QgsMapMouseEvent *event
 
   std::unique_ptr< QgsAnnotationPointTextItem > createdItem = std::make_unique< QgsAnnotationPointTextItem >( tr( "Text" ), layerPoint );
   createdItem->setAlignment( Qt::AlignLeft );
-  createdItem->setFormat( QgsStyle::defaultStyle()->defaultTextFormat( QgsStyle::TextFormatContext::Labeling ) );
+  createdItem->setFormat( QgsStyle::defaultTextFormatForProject( QgsProject::instance(), QgsStyle::TextFormatContext::Labeling ) );
   // newly created point text items default to using symbology reference scale at the current map scale
   createdItem->setUseSymbologyReferenceScale( true );
   createdItem->setSymbologyReferenceScale( canvas()->scale() );

src/gui/labeling/qgslabelinggui.cpp

@@ -344,7 +344,7 @@ void QgsLabelingGui::setLayer( QgsMapLayer *mapLayer )
     mGeometryGeneratorGroupBox->setCollapsed( true );
   mGeometryGeneratorType->setCurrentIndex( mGeometryGeneratorType->findData( mSettings.geometryGeneratorType ) );
 
-  updateWidgetForFormat( mSettings.format().isValid() ? mSettings.format() : QgsStyle::defaultStyle()->defaultTextFormat( QgsStyle::TextFormatContext::Labeling ) );
+  updateWidgetForFormat( mSettings.format().isValid() ? mSettings.format() : QgsStyle::defaultTextFormatForProject( QgsProject::instance(), QgsStyle::TextFormatContext::Labeling ) );
 
   mFieldExpressionWidget->setRow( -1 );
   mFieldExpressionWidget->setField( mSettings.fieldName );

src/gui/qgstextformatwidget.cpp

@@ -53,7 +53,7 @@ QgsTextFormatWidget::QgsTextFormatWidget( const QgsTextFormat &format, QgsMapCan
   initWidget();
   setWidgetMode( Text );
   populateDataDefinedButtons();
-  updateWidgetForFormat( format.isValid() ? format : QgsStyle::defaultStyle()->defaultTextFormat() );
+  updateWidgetForFormat( format.isValid() ? format : QgsStyle::defaultTextFormatForProject( QgsProject::instance() ) );
 }
 
 QgsTextFormatWidget::QgsTextFormatWidget( QgsMapCanvas *mapCanvas, QWidget *parent, Mode mode, QgsVectorLayer *layer )