Add flag to indicate that vector tile provider matrix set should

always be used for the layer (as opposed to any previously
stored matrix sets)

For some vector tile data providers this is more appropriate --
specifically for those with tilemap information where we MUST
ensure that the tilemap matches the data source or missing
tiles may be present. (If we store the matrix set information
in projects then loading older projects may mean that a stored
tilemap is out-of-sync with the actual data source's current
tilemap).

python/core/auto_additions/qgis.py

@@ -3614,6 +3614,13 @@ Qgis.FeatureSymbologyExport.__doc__ = 'Options for exporting features considerin
 # --
 Qgis.FeatureSymbologyExport.baseClass = Qgis
 # monkey patching scoped based enum
+Qgis.VectorTileProviderFlag.AlwaysUseTileMatrixSetFromProvider.__doc__ = "Vector tile layer must always use the tile matrix set from the data provider, and should never store, restore or override the definition of this matrix set."
+Qgis.VectorTileProviderFlag.__doc__ = 'Flags for vector tile data providers.\n\n.. versionadded:: 3.32\n\n' + '* ``AlwaysUseTileMatrixSetFromProvider``: ' + Qgis.VectorTileProviderFlag.AlwaysUseTileMatrixSetFromProvider.__doc__
+# --
+Qgis.VectorTileProviderFlag.baseClass = Qgis
+Qgis.VectorTileProviderFlags.baseClass = Qgis
+VectorTileProviderFlags = Qgis  # dirty hack since SIP seems to introduce the flags in module
+# monkey patching scoped based enum
 Qgis.VectorTileProviderCapability.ReadLayerMetadata.__doc__ = "Provider can read layer metadata from data store. See QgsDataProvider.layerMetadata()"
 Qgis.VectorTileProviderCapability.__doc__ = 'Enumeration with capabilities that vector tile data providers might implement.\n\n.. versionadded:: 3.32\n\n' + '* ``ReadLayerMetadata``: ' + Qgis.VectorTileProviderCapability.ReadLayerMetadata.__doc__
 # --

python/core/auto_generated/qgis.sip.in

@@ -2047,6 +2047,14 @@ The development version
       PerSymbolLayer
     };
 
+    enum class VectorTileProviderFlag
+    {
+      AlwaysUseTileMatrixSetFromProvider,
+    };
+
+    typedef QFlags<Qgis::VectorTileProviderFlag> VectorTileProviderFlags;
+
+
     enum class VectorTileProviderCapability
     {
       ReadLayerMetadata,
@@ -2217,6 +2225,8 @@ QFlags<Qgis::DatabaseProviderConnectionCapability2> operator|(Qgis::DatabaseProv
 
 QFlags<Qgis::VectorFileWriterCapability> operator|(Qgis::VectorFileWriterCapability f1, QFlags<Qgis::VectorFileWriterCapability> f2);
 
+QFlags<Qgis::VectorTileProviderFlag> operator|(Qgis::VectorTileProviderFlag f1, QFlags<Qgis::VectorTileProviderFlag> f2);
+
 QFlags<Qgis::VectorTileProviderCapability> operator|(Qgis::VectorTileProviderCapability f1, QFlags<Qgis::VectorTileProviderCapability> f2);
 
 

src/core/qgis.h

@@ -3553,6 +3553,25 @@ class CORE_EXPORT Qgis
     };
     Q_ENUM( FeatureSymbologyExport )
 
+    /**
+     * Flags for vector tile data providers.
+     *
+     * \since QGIS 3.32
+     */
+    enum class VectorTileProviderFlag : int
+    {
+      AlwaysUseTileMatrixSetFromProvider = 1 << 1, //!< Vector tile layer must always use the tile matrix set from the data provider, and should never store, restore or override the definition of this matrix set.
+    };
+    Q_ENUM( VectorTileProviderFlag )
+
+    /**
+     * Vector tile data provider flags.
+     *
+     * \since QGIS 3.32
+     */
+    Q_DECLARE_FLAGS( VectorTileProviderFlags, VectorTileProviderFlag )
+    Q_FLAG( VectorTileProviderFlags )
+
     /**
      * Enumeration with capabilities that vector tile data providers might implement.
      * \since QGIS 3.32
@@ -3745,6 +3764,7 @@ Q_DECLARE_OPERATORS_FOR_FLAGS( Qgis::LabelLinePlacementFlags )
 Q_DECLARE_OPERATORS_FOR_FLAGS( Qgis::LabelPolygonPlacementFlags )
 Q_DECLARE_OPERATORS_FOR_FLAGS( Qgis::DatabaseProviderConnectionCapabilities2 )
 Q_DECLARE_OPERATORS_FOR_FLAGS( Qgis::VectorFileWriterCapabilities )
+Q_DECLARE_OPERATORS_FOR_FLAGS( Qgis::VectorTileProviderFlags )
 Q_DECLARE_OPERATORS_FOR_FLAGS( Qgis::VectorTileProviderCapabilities )
 
 // hack to workaround warnings when casting void pointers

src/core/vectortile/qgsvectortiledataprovider.cpp

@@ -32,6 +32,11 @@ QgsVectorTileDataProvider::QgsVectorTileDataProvider( const QgsVectorTileDataPro
   setTransformContext( other.transformContext() );
 }
 
+Qgis::VectorTileProviderFlags QgsVectorTileDataProvider::providerFlags() const
+{
+  return Qgis::VectorTileProviderFlags();
+}
+
 Qgis::VectorTileProviderCapabilities QgsVectorTileDataProvider::providerCapabilities() const
 {
   return Qgis::VectorTileProviderCapabilities();

src/core/vectortile/qgsvectortiledataprovider.h

@@ -58,6 +58,12 @@ class CORE_EXPORT QgsVectorTileDataProvider : public QgsDataProvider
      */
     QgsVectorTileDataProvider &operator=( const QgsVectorTileDataProvider &other ) = delete;
 
+    /**
+     * Returns flags reflecting the behavior of the data provider.
+     * \since QGIS 3.32
+     */
+    virtual Qgis::VectorTileProviderFlags providerFlags() const;
+
     /**
      * Returns flags containing the supported capabilities of the data provider.
      * \since QGIS 3.32

src/core/vectortile/qgsvectortilelayer.cpp

@@ -154,12 +154,15 @@ bool QgsVectorTileLayer::readXml( const QDomNode &layerNode, QgsReadWriteContext
 
   setValid( loadDataSource() );
 
-  const QDomElement matrixSetElement = layerNode.firstChildElement( QStringLiteral( "matrixSet" ) );
+  if ( !mDataProvider || !( qobject_cast< QgsVectorTileDataProvider * >( mDataProvider.get() )->providerFlags() & Qgis::VectorTileProviderFlag::AlwaysUseTileMatrixSetFromProvider ) )
-  if ( !matrixSetElement.isNull() )
   {
-    mMatrixSet.readXml( matrixSetElement, context );
+    const QDomElement matrixSetElement = layerNode.firstChildElement( QStringLiteral( "matrixSet" ) );
-    setCrs( mMatrixSet.crs() );
+    if ( !matrixSetElement.isNull() )
+    {
+      mMatrixSet.readXml( matrixSetElement, context );
+    }
   }
+  setCrs( mMatrixSet.crs() );
 
   QString errorMsg;
   if ( !readSymbology( layerNode, errorMsg, context ) )
@@ -176,7 +179,11 @@ bool QgsVectorTileLayer::writeXml( QDomNode &layerNode, QDomDocument &doc, const
   QDomElement mapLayerNode = layerNode.toElement();
   mapLayerNode.setAttribute( QStringLiteral( "type" ), QgsMapLayerFactory::typeToString( Qgis::LayerType::VectorTile ) );
 
-  mapLayerNode.appendChild( mMatrixSet.writeXml( doc, context ) );
+  if ( !mDataProvider || !( qobject_cast< QgsVectorTileDataProvider * >( mDataProvider.get() )->providerFlags() & Qgis::VectorTileProviderFlag::AlwaysUseTileMatrixSetFromProvider ) )
+  {
+    mapLayerNode.appendChild( mMatrixSet.writeXml( doc, context ) );
+  }
+
 
   // add provider node
   if ( mDataProvider )