Delay the construction of Surfaces and the surface maps until they are needed

and are obtained with `map()`. Delete the move constructor since std::once_flag
is not movable. initialize() now can be const, but this is only called within
DD4hep. Interface for users doesn't change, except now the message with the
number of elements in each surface map appears later, when they are built.

Author: jmcarcell

DDRec/include/DDRec/SurfaceManager.h

@@ -41,17 +41,13 @@ namespace dd4hep {
       SurfaceManager(const Detector& theDetector);
 
       /// No default constructor
-#if defined(G__ROOT)
-      SurfaceManager() = default ;
-#else
       SurfaceManager() = delete ;
-#endif
 
       ~SurfaceManager() = default;
       SurfaceManager(const SurfaceManager&) = delete;
       SurfaceManager& operator=(const SurfaceManager&) = delete;
-      SurfaceManager(SurfaceManager&&) = default;
-      SurfaceManager& operator=(SurfaceManager&&) = default;
+      SurfaceManager(SurfaceManager&&) = delete;
+      SurfaceManager& operator=(SurfaceManager&&) = delete;
 
 
       /** Get the maps of all surfaces associated to the given detector or
@@ -68,9 +64,11 @@ namespace dd4hep {
 
 
       /// initialize all known surface maps
-      void initialize(const Detector& theDetector) ;
+      void initialize(const Detector& theDetector) const;
 
-      SurfaceMapsMap _map ;
+      mutable SurfaceMapsMap  _map{} ;
+      const Detector& _theDetector ;
+      mutable std::once_flag  _initializedFlag{} ;
     };
 
   } /* namespace rec */

DDRec/src/SurfaceManager.cpp

@@ -15,25 +15,27 @@
 #include "DDRec/SurfaceHelper.h"
 #include "DD4hep/VolumeManager.h"
 #include "DD4hep/Detector.h"
+#include "DD4hep/Printout.h"
 
 #include <sstream>
 
 namespace dd4hep {
   namespace rec {
 
-    SurfaceManager::SurfaceManager(const Detector& theDetector){
+    SurfaceManager::SurfaceManager(const Detector& theDetector) : _theDetector(theDetector) {
 
       // have to make sure the volume manager is populated once in order to have
       // the volumeIDs attached to the DetElements
 
       VolumeManager::getVolumeManager(theDetector);
 
-      initialize(theDetector) ;
     }
 
 
     const SurfaceMap* SurfaceManager::map( const std::string& name ) const {
 
+      std::call_once( _initializedFlag, &SurfaceManager::initialize, this, _theDetector ) ;
+
       SurfaceMapsMap::const_iterator it = _map.find( name ) ;
 
       if( it != _map.end() ){
@@ -44,7 +46,7 @@ namespace dd4hep {
       return nullptr ;
     }
 
-    void SurfaceManager::initialize(const Detector& description) {
+    void SurfaceManager::initialize(const Detector& description) const {
 
       for(const auto& type : description.detectorTypes()) {
 
@@ -75,6 +77,8 @@ namespace dd4hep {
         }
       }
 
+      printout(INFO,"SurfaceManager","%s" , description.extension<SurfaceManager>()->toString().c_str() );
+
     }
 
     std::string SurfaceManager::toString() const {

DDRec/src/plugins/createSurfaceManager.cpp

@@ -40,10 +40,10 @@ namespace dd4hep{
     static long createSurfaceManager(Detector& description, int /*argc*/, char** /*argv*/) {
 
       printout(INFO,"InstallSurfaceManager","**** running plugin InstallSurfaceManager ! " );
+      printout(INFO,"InstallSurfaceManager","**** the map of surfaces will be created on first access ! " );
 
       description.addExtension<SurfaceManager>(  new SurfaceManager(description) ) ;
 
-      printout(INFO,"InstallSurfaceManager","%s" , description.extension<SurfaceManager>()->toString().c_str() );
 
       return 1;
     }