Modify Geant4Config.cmake to set data files env variables for LHCb projects

cmake/Modules/G4ConfigureCMakeHelpers.cmake

@@ -256,10 +256,16 @@ configure_file(
   ${PROJECT_BINARY_DIR}/InstallTreeFiles/Geant4Config.cmake
   @ONLY
   )
+configure_file(
+  ${PROJECT_SOURCE_DIR}/cmake/Templates/LHCbConfigSettings.cmake.in
+  ${PROJECT_BINARY_DIR}/InstallTreeFiles/LHCbConfigSettings.cmake
+  @ONLY
+  )
 
 # Install the config, config versioning and use files
 install(FILES
   ${PROJECT_BINARY_DIR}/InstallTreeFiles/Geant4Config.cmake
+  ${PROJECT_BINARY_DIR}/InstallTreeFiles/LHCbConfigSettings.cmake
   ${PROJECT_BINARY_DIR}/Geant4ConfigVersion.cmake
   ${PROJECT_BINARY_DIR}/G4EXPATShim.cmake
   ${PROJECT_BINARY_DIR}/G4FreetypeShim.cmake

cmake/Templates/Geant4Config.cmake.in

@@ -712,5 +712,8 @@ foreach(_comp ${Geant4_FIND_COMPONENTS})
   endif()
 endforeach()
 
+# include special settings needed for LHCb projects
+include("${CMAKE_CURRENT_LIST_DIR}/LHCbConfigSettings.cmake")
+
 # And we should be done...
 

cmake/Templates/LHCbConfigSettings.cmake.in

+# Helper to define special settings needed by downstream LHCb projects
+
+# Set environment variables for Geant4 data files (only if we have the lhcb_env command)
+if(COMMAND lhcb_env)
+    lhcb_env(DEFAULT G4DATA "@GEANT4_INSTALL_DATADIR@")
+    foreach(_g4dataset_name IN LISTS Geant4_DATASETS)
+        string(REPLACE "@GEANT4_INSTALL_DATADIR@" "" _g4dataset_path "${Geant4_DATASET_${_g4dataset_name}_PATH}")
+        lhcb_env(SET "${Geant4_DATASET_${_g4dataset_name}_ENVVAR}" "\${G4DATA}/${_g4dataset_path}")
+    endforeach()
+endif()