Deprecate method without transformContext

python/core/auto_generated/processing/qgsprocessingutils.sip.in

@@ -176,10 +176,22 @@ temporary layer store.
    available in Python bindings as createFeatureSink()
 %End
 
-    static QgsRectangle combineLayerExtents( const QList<QgsMapLayer *> &layers, const QgsCoordinateReferenceSystem &crs = QgsCoordinateReferenceSystem() );
+
+    static QgsRectangle combineLayerExtents( const QList<QgsMapLayer *> &layers, const QgsCoordinateReferenceSystem &crs, const QgsCoordinateTransformContext &transformContext );
+%Docstring
+Combines the extent of several map ``layers``. If specified, the target ``crs``
+will be used to transform the layer's extent to the desired output reference system
+using the specified ``transformContext``.
+
+.. versionadded:: 3.10
+%End
+
+ static QgsRectangle combineLayerExtents( const QList<QgsMapLayer *> &layers, const QgsCoordinateReferenceSystem &crs = QgsCoordinateReferenceSystem() ) /Deprecated/;
 %Docstring
 Combines the extent of several map ``layers``. If specified, the target ``crs``
 will be used to transform the layer's extent to the desired output reference system.
+
+.. deprecated:: Use version with transformContext argument instead
 %End
 
     static QVariant generateIteratingDestination( const QVariant &input, const QVariant &id, QgsProcessingContext &context );

src/core/processing/qgsprocessingutils.cpp

@@ -627,7 +627,7 @@ void QgsProcessingUtils::createFeatureSinkPython( QgsFeatureSink **sink, QString
 }
 
 
-QgsRectangle QgsProcessingUtils::combineLayerExtents( const QList<QgsMapLayer *> &layers, const QgsCoordinateReferenceSystem &crs )
+QgsRectangle QgsProcessingUtils::combineLayerExtents( const QList<QgsMapLayer *> &layers, const QgsCoordinateReferenceSystem &crs, const QgsCoordinateTransformContext &transformContext )
 {
   QgsRectangle extent;
   for ( const QgsMapLayer *layer : layers )
@@ -638,7 +638,7 @@ QgsRectangle QgsProcessingUtils::combineLayerExtents( const QList<QgsMapLayer *>
     if ( crs.isValid() )
     {
       //transform layer extent to target CRS
-      QgsCoordinateTransform ct( layer->crs(), crs, QgsProject::instance()->transformContext() );
+      QgsCoordinateTransform ct( layer->crs(), crs, transformContext );
       try
       {
         QgsRectangle reprojExtent = ct.transformBoundingBox( layer->extent() );
@@ -659,6 +659,12 @@ QgsRectangle QgsProcessingUtils::combineLayerExtents( const QList<QgsMapLayer *>
   return extent;
 }
 
+// Deprecated
+QgsRectangle QgsProcessingUtils::combineLayerExtents( const QList<QgsMapLayer *> &layers, const QgsCoordinateReferenceSystem &crs )
+{
+  return QgsProcessingUtils::combineLayerExtents( layers, crs, QgsCoordinateTransformContext( ) );
+}
+
 QVariant QgsProcessingUtils::generateIteratingDestination( const QVariant &input, const QVariant &id, QgsProcessingContext &context )
 {
   if ( !input.isValid() )

src/core/processing/qgsprocessingutils.h

@@ -213,11 +213,21 @@ class CORE_EXPORT QgsProcessingUtils
      */
     static void createFeatureSinkPython( QgsFeatureSink **sink SIP_OUT SIP_TRANSFERBACK, QString &destination SIP_INOUT, QgsProcessingContext &context, const QgsFields &fields, QgsWkbTypes::Type geometryType, const QgsCoordinateReferenceSystem &crs, const QVariantMap &createOptions = QVariantMap() ) SIP_THROW( QgsProcessingException ) SIP_PYNAME( createFeatureSink );
 
+
+    /**
+     * Combines the extent of several map \a layers. If specified, the target \a crs
+     * will be used to transform the layer's extent to the desired output reference system
+     * using the specified \a transformContext.
+     * \since QGIS 3.10
+     */
+    static QgsRectangle combineLayerExtents( const QList<QgsMapLayer *> &layers, const QgsCoordinateReferenceSystem &crs, const QgsCoordinateTransformContext &transformContext );
+
     /**
      * Combines the extent of several map \a layers. If specified, the target \a crs
      * will be used to transform the layer's extent to the desired output reference system.
+     * \deprecated Use version with transformContext argument instead
      */
-    static QgsRectangle combineLayerExtents( const QList<QgsMapLayer *> &layers, const QgsCoordinateReferenceSystem &crs = QgsCoordinateReferenceSystem() );
+    Q_DECL_DEPRECATED static QgsRectangle combineLayerExtents( const QList<QgsMapLayer *> &layers, const QgsCoordinateReferenceSystem &crs = QgsCoordinateReferenceSystem() ) SIP_DEPRECATED;
 
     /**
      * Converts an \a input parameter value for use in source iterating mode, where one individual sink