Respect project "avoid tile artefacts" setting when rendering

a project using WMS services

Fixes #37679

python/server/auto_generated/qgsserverprojectutils.sip.in

@@ -165,6 +165,21 @@ Returns the tile buffer in pixels for WMS images defined in a QGIS project.
 :return: tile buffer if defined in project, 0 otherwise.
 
 .. versionadded:: 3.10
+%End
+
+  bool wmsRenderMapTiles( const QgsProject &project );
+%Docstring
+Returns ``True`` if WMS requests should use the QgsMapSettings.RenderMapTile flag,
+so that no visible artefacts are visible between adjacent tiles.
+
+This flag can slow down rendering considerably, so it is only used if the corresponding
+setting is enabled in the project.
+
+:param project: the QGIS project
+
+:return: ``True`` if the flag should be used, or ``False`` if not.
+
+.. versionadded:: 3.18
 %End
 
   int wmsMaxAtlasFeatures( const QgsProject &project );

src/server/qgsserverprojectutils.cpp

@@ -389,3 +389,8 @@ QString QgsServerProjectUtils::wmtsServiceUrl( const QgsProject &project )
 {
   return project.readEntry( QStringLiteral( "WMTSUrl" ), QStringLiteral( "/" ), "" );
 }
+
+bool QgsServerProjectUtils::wmsRenderMapTiles( const QgsProject &project )
+{
+  return project.readBoolEntry( QStringLiteral( "RenderMapTile" ), QStringLiteral( "/" ), false );
+}

src/server/qgsserverprojectutils.h

@@ -171,6 +171,20 @@ namespace QgsServerProjectUtils
    */
   SERVER_EXPORT int wmsTileBuffer( const QgsProject &project );
 
+  /**
+   * Returns TRUE if WMS requests should use the QgsMapSettings::RenderMapTile flag,
+   * so that no visible artefacts are visible between adjacent tiles.
+   *
+   * This flag can slow down rendering considerably, so it is only used if the corresponding
+   * setting is enabled in the project.
+   *
+   * \param project the QGIS project
+   * \returns TRUE if the flag should be used, or FALSE if not.
+   *
+   * \since QGIS 3.18
+   */
+  SERVER_EXPORT bool wmsRenderMapTiles( const QgsProject &project );
+
   /**
    * Returns the maximum number of atlas features which can be printed in a request
    * \param project the QGIS project

src/server/services/wms/qgswmsrendercontext.cpp

@@ -150,6 +150,11 @@ int QgsWmsRenderContext::tileBuffer() const
   return tileBuffer;
 }
 
+bool QgsWmsRenderContext::renderMapTiles() const
+{
+  return QgsServerProjectUtils::wmsRenderMapTiles( *mProject );
+}
+
 int QgsWmsRenderContext::precision() const
 {
   int precision = QgsServerProjectUtils::wmsFeatureInfoPrecision( *mProject );

src/server/services/wms/qgswmsrendercontext.h

@@ -156,6 +156,17 @@ namespace QgsWms
        */
       int tileBuffer() const;
 
+      /**
+       * Returns TRUE if WMS requests should use the QgsMapSettings::RenderMapTile flag,
+       * so that no visible artefacts are visible between adjacent tiles.
+       *
+       * This flag can slow down rendering considerably, so it is only used if the corresponding
+       * if explicitly opted in.
+       *
+       * \since QGIS 3.18
+       */
+      bool renderMapTiles() const;
+
       /**
        * Returns the precision to use according to the current configuration.
        */

src/server/services/wms/qgswmsrenderer.cpp

@@ -1165,6 +1165,8 @@ namespace QgsWms
     // enable rendering optimization
     mapSettings.setFlag( QgsMapSettings::UseRenderingOptimization );
 
+    mapSettings.setFlag( QgsMapSettings::RenderMapTile, mContext.renderMapTiles() );
+
     // set selection color
     mapSettings.setSelectionColor( mProject->selectionColor() );
   }