14. The method according to claim 13 , wherein the generated data structure comprises a list of the intermediate representations being generated, each entry in the created list referencing a corresponding one of the intermediate representations and is associated with a state variable defining the progress of generating the corresponding intermediate representation.
14. The method according to claim 13 , wherein the generated data structure comprises a list of the intermediate representations being generated, each entry in the created list referencing a corresponding one of the intermediate representations and is associated with a state variable defining the progress of generating the corresponding intermediate representation. 16. The method according to claim 14 , wherein the least two intermediate representations consecutive in z-order are selected by determining, within the list, a sub-list of intermediate representations associated with ‘FINISHED’ state variable.