working on structure destination, WIP

l3backend-testphase.dtx

@@ -1757,14 +1757,22 @@
 % that if structure destinations are used, they should be used always. So we define
 % alternative commands which can be activated by mapping them to the standard backend commands.
 %
+% The needed code differ depending on if structure objects use standard or indexed object names.
+% At the end we will probably always use indexed objects, but for now we offer
+% both options.
+% 
 % \begin{macro}{\l_pdf_current_structure_destination_tl}
 %
-% This commands holds the name of the structure object to use in the next command
+% This command holds the name of the structure object to use in the following commands
 % which creates a destination. The code which activates structure destinations
 % must also ensure that it has a sensible, expandable content. \pkg{tagpdf} for example
 % will define it as
 % \begin{verbatim}
 % \tl_set:Nn \l_pdf_current_structure_destination_tl { __tag/struct/\g__tag_struct_stack_current_tl }
+% \end{verbatim} 
+% or if indexed structure object names are used
+% \begin{verbatim}
+% \tl_set:Nn \l_pdf_current_structure_destination_tl { {__tag/struct}{\g__tag_struct_stack_current_tl} }
 % \end{verbatim}
 % \begin{macrocode}
 %<*drivers>
@@ -1778,21 +1786,30 @@
 % \__pdf_backend_destination:nn -> \__pdf_backend_structure_destination:nn
 % \__pdf_backend_destination:nnnn -> \__pdf_backend_structure_destination:nnnn
 % \__pdf_backend_link_begin_goto:nnw -> \__pdf_backend_link_begin_structure_goto:nnw
+% \__pdf_backend_destination:nn -> \__pdf_backend_indexed_structure_destination:nn
+% \__pdf_backend_destination:nnnn -> \__pdf_backend_indexed_structure_destination:nnnn
+% \__pdf_backend_link_begin_goto:nnw -> \__pdf_backend_indexed_link_begin_structure_goto:nnw 
 % \end{verbatim}
 %
 % Activating means mapping them onto the original commands. Be aware that not
 % all engines and compilation routes support structure destinations, for them
 % the command will be a no-op.
 %
-% \begin{macro}{\pdf_activate_structure_destination:}
+% \begin{macro}{\pdf_activate_structure_destination:,\pdf_activate_indexed_structure_destination:}
 % \begin{macrocode}
 %<*drivers>
 \cs_new_protected:Npn \pdf_activate_structure_destination:
  {
- \cs_gset_eq:NN \@@_backend_destination:nn \@@_backend_structure_destination:nn
- \cs_gset_eq:NN \@@_backend_destination:nnnn \@@_backend_structure_destination:nnnn
+ \cs_gset_eq:NN \@@_backend_destination:nn  \@@_backend_structure_destination:nn
+ \cs_gset_eq:NN \@@_backend_destination:nnnn  \@@_backend_structure_destination:nnnn
  \cs_gset_eq:NN \@@_backend_link_begin_goto:nnw \@@_backend_link_begin_structure_goto:nnw
  }
+\cs_new_protected:Npn \pdf_activate_indexed_structure_destination:
+ {
+ \cs_gset_eq:NN \@@_backend_destination:nn \@@_backend_indexed_structure_destination:nn
+ \cs_gset_eq:NN \@@_backend_destination:nnnn \@@_backend_indexed_structure_destination:nnnn
+ \cs_gset_eq:NN \@@_backend_link_begin_goto:nnw \@@_backend_indexed_link_begin_structure_goto:nnw
+ }
 %</drivers>
 % \end{macrocode}
 % \end{macro}