[C/WEB] Generic solution for non-TEXMF programs.

Finally I was able to wrap my head around the 'toc-to-front' stuff!

For standard WEB and CWEB programs, place the patched '\con' exactly
between the very first '\MN' and the following '\eject'.  At the same
time, ackowledge any local definition of '\topofcontents' from the
preamble.  For this 'pdfwebtocfront.tex' must be '\input' at the very
end of the preamble, right before the first '\N'.

The four programs 'mf.web', 'tex,web', 'pdftex.web', and 'xetex.web'
define their special version of '\N' in the preamble, so the old variant
of the '\con in \N' mechanism is preserved.  Their tables-of-contents
use a bare layout anyway.

git-svn-id: svn://tug.org/texlive/trunk@55604 c570f23f-e606-0410-a88d-b1316a301751

2 files changed, 43 insertions, 31 deletions

diff --git a/Build/source/texk/web2c/cwebdir/ChangeLog b/Build/source/texk/web2c/cwebdir/ChangeLog
index c36725a8929..0ab5f32dd6e 100644
--- a/Build/source/texk/web2c/cwebdir/ChangeLog
+++ b/Build/source/texk/web2c/cwebdir/ChangeLog
@@ -1,5 +1,10 @@
 2020-06-20  Andreas Scherer  <https://ascherer.github.io>
 
+	* texinputs/pdfwebtocfront.tex: Generic solution for the headers in
+	WEB and CWEB programs (with four special cases with their own '\N').
+
+2020-06-20  Andreas Scherer  <https://ascherer.github.io>
+
 	* comm-w2c.ch: Clarify triple responsibility.
 
 2020-06-19  Andreas Scherer  <https://ascherer.github.io>
diff --git a/Build/source/texk/web2c/cwebdir/texinputs/pdfwebtocfront.tex b/Build/source/texk/web2c/cwebdir/texinputs/pdfwebtocfront.tex
index f8c8eea9ad9..ac2daac790c 100644
--- a/Build/source/texk/web2c/cwebdir/texinputs/pdfwebtocfront.tex
+++ b/Build/source/texk/web2c/cwebdir/texinputs/pdfwebtocfront.tex
@@ -1,6 +1,6 @@
 % pdfwebtofront.tex
 % Code from knuth.drv in https://github.com/oberdiek/latex-tds
-% 2020/06/19 v1.2 by Andreas Scherer.
+% 2020/06/20 v2.0 by Andreas Scherer.
 %
 % This file is part of project https://github.com/ascherer/cwebbin
 % and may be distributed under the MIT License or the LaTeX Project
@@ -20,7 +20,6 @@
   % Redefine '\con' to be invoked before the first '\N' (starred section).
   \let\ORGcon\con
   \def\con{%
-    \def\:{\par\hangindent 2em} % Fix for 'bibtex.web'.
     % reduce size of PDF pages for more screen space
     \pdfpagewidth=\pagewidth  \advance\pdfpagewidth by 2cm
     \pdfpageheight=\pageheight \advance\pdfpageheight by 3cm
@@ -30,26 +29,13 @@
     \begingroup
       \let\end\relax
       \ORGcon
-      % let's start with section '1'; the '\gtitle' should be set,
-      % e.g. to 'Introduction', right before '\input pdfwebtocfront'.
-      \ifx\undefined\gdepth \mark{{{\tensy x}1}{\the\gtitle}} % WEB
-      \else \mark{{{\tensy x}1}0{\the\gtitle}}\fi % CWEB
-      \eject % set '\botmark' on TOC, hence '\topmark' on next page.
     \endgroup
     \let\con\end
   }%
-  % Redefine '\N’ to invoke redefined '\con' before switching back
-  % to original '\N'.
-  \expandafter\let\csname ORGN\expandafter\endcsname
-                  \csname N\endcsname
-  \expandafter\outer\expandafter\def\csname N\endcsname{%
-    \con
-    \expandafter\let\csname N\expandafter\endcsname
-                    \csname ORGN\endcsname
-    \csname N\endcsname
-  }%
-  % Special variant of the above for 'mf.web' and 'tex.web'.  They put
-  % their tables-of-contents on a sparse 'page 2' and start on page '3'.
+  % Special variant for 'mf.web' and 'tex.web' (et al.).
+  % They all define a peculiar version of '\N' in their preamble.
+  % And they put their tables-of-contents on a sparse 'page 2' and
+  % start the main body on page '3'.
   \begingroup
     \edef\x{\jobname}%
     \edef\y{\detokenize{tex}}%
@@ -62,18 +48,39 @@
     \ifx\x\y \texmftrue\fi\fi\fi\fi
   \expandafter\endgroup\iftexmf %
     \def\contentspagenumber{2}%
-    \let\ORGpageno\pageno
-    \def\pageno{%
-      \let\pageno\ORGpageno
-      \expandafter\let\csname ORGN\expandafter\endcsname
-                      \csname N\endcsname
-      \expandafter\outer\expandafter\def\csname N\endcsname{%
-        \con
-        \expandafter\let\csname N\expandafter\endcsname
-                        \csname ORGN\endcsname
-        \csname N\endcsname
-      }%
-      \pageno
+    \expandafter\let\csname ORGN\expandafter\endcsname
+                    \csname N\endcsname
+    \expandafter\outer\expandafter\def\csname N\endcsname{%
+      \titletrue \pageno=\contentspagenumber \con
+      \expandafter\let\csname N\expandafter\endcsname
+                      \csname ORGN\endcsname
+      \csname N\endcsname
+    }%
+  \else % Much more general approach for WEB and CWEB programs.
+    % In fact, '\con' will be invoked _inside_ the first '\N' right _after_
+    % '\MN', but _before_ '\eject'.  And '\topofcontents' gets in the twist
+    % as well.
+    \let\ORGtopofcontents\topofcontents
+    \def\topofcontents{%
+      \def\:{\par\hangindent 2em} % Fix for 'bibtex.web'; from '\def\fin'.
+      \ORGtopofcontents
+      \let\topofcontents\relax
+    }%
+    % Squeeze '\con' between '\MN' and '\eject' in the very first '\N'.
+    \expandafter\let\csname ORGvfil\expandafter\endcsname
+                    \csname vfil\endcsname
+    \expandafter\let\csname ORGeject\expandafter\endcsname
+                    \csname eject\endcsname
+    \expandafter\outer\expandafter\def\csname vfil\endcsname{%
+      \let\eject\relax
+      \titletrue % prepare to output the table of contents
+      \topofcontents \con
+      \advance\pageno by -1\relax
+      \expandafter\let\csname vfil\expandafter\endcsname
+                      \csname ORGvfil\endcsname
+      \expandafter\let\csname eject\expandafter\endcsname
+                      \csname ORGeject\endcsname
+      \vfil
     }%
   \fi
 \fi