add \tag_spacechar_on: and \tag_spacechar_off:

CHANGELOG.md

@@ -5,6 +5,11 @@ All notable changes to the `tagpdf` package since the
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 this project uses date-based 'snapshot' version identifiers.
 
+## [Unreleased]
+### Added
+ - \tag_spacechar_on:, \tag_spacechar_off: to locally switch off 
+   the real space chars.  
+
 ## [2024-03-27]
 Version 0.99a
 ### Fixed

doc/tagpdf.tex

@@ -2434,6 +2434,20 @@ \section{\enquote{Real} space glyphs}\label{sec:spacechars}
 \pkg{tagpdf} defines this command also for luatex -- attention if can
 perhaps insert break points.
 
+\begin{docCommands}
+ {
+  {doc name=tag_space_off:}
+  {doc name=tag_space_on:}
+ }
+\end{docCommand}
+
+The commands allow to switch on and off the insertion of space chars.
+With pdftex they map to primitive \cs{pdfinterwordspaceoff} and
+and \cs{pdfinterwordspaceon} which insert a whatsits and so act globally.
+The luatex implementation uses an attribute which is also set globally to stay
+more or less consistent with pdftex. In dvi-mode the commands do nothing.
+
+
 \section{Structure destinations}\label{sec:struct-dest}
 
  Standard destinations (anchors for internal links) consist of a

tagpdf-space.dtx

@@ -161,6 +161,66 @@
         \group_end:
       }
   }
+%    \end{macrocode}
+% 
+% We need also a command to interrupt the insertion of real space
+% chars in places where we want to insert manually special spaces. 
+% In pdftex this can be done with \cs{pdfinterwordspaceoff}
+% and \cs{pdfinterwordspaceon}. These commands insert whatsits
+% and this mean they act globally. In luatex a attribute is
+% used to this effect, for consistency this is also set globally.
+% 
+%
+% \begin{macro}{\tag_spacechar_on:,\tag_spacechar_off:}
+% The off command sets the attributes in luatex.
+%    \begin{macrocode}
+\cs_new_protected:Npn \tag_spacechar_off: {}
+\cs_new_protected:Npn \tag_spacechar_on: {}
+
+\sys_if_engine_luatex:T
+ {
+   \cs_set_protected:Npn \tag_spacechar_off: 
+     {
+       \lua_now:e 
+         {
+           tex.setattribute
+            (
+             "global",
+             luatexbase.attributes.g_@@_interwordspaceOff_attr,
+             1
+            )
+         }
+     }
+   \cs_set_protected:Npn \tag_spacechar_on: 
+     {
+       \lua_now:e 
+         {
+           tex.setattribute
+            (
+             "global",
+             luatexbase.attributes.g_@@_interwordspaceOff_attr,
+             -2147483647
+            )
+         }
+     }
+ }
+\sys_if_engine_pdftex:T
+  {
+    \sys_if_output_pdf:T
+      {
+       \cs_set_protected:Npn \tag_spacechar_off: 
+          {
+            \pdfinterwordspaceoff
+          }       
+        \cs_set_protected:Npn \tag_spacechar_on: 
+          {
+            \pdfinterwordspaceon
+          }         
+      }
+  }    
+%    \end{macrocode}
+% \end{macro}
+%    \begin{macrocode}
 %</package>
 %    \end{macrocode}
 % \end{macro}