[mdoc]: Align trap mgmt more closely with man(7).

* tmac/mdoc/doc-common: Call new macro (see below)
  `doc-set-up-continuous-rendering` when initializing, if that is mode
  is configured.

  (doc-ne): New macro replaces `ne` request in continuous rendering
  mode.  It extends the page length by the amount in the argument or by
  1v if none given.

  (doc-bp): New macro replaces `bp` request in continuous rendering
  mode, setting the page length to the vertical drawing position.

  (doc-set-up-continuous-rendering): New macro renames requests to
  emplace the foregoing.

  (Dd): Interpret this macro call strictly as starting a new mdoc(7)
  document.  (andoc.tmac already makes this assumption, and has for over
  20 years.  groff_mdoc(7) and mandoc_mdoc(7) also prescribe the
  sequence `Dd`, `Dt`, `Os`.)  We require this invariant even more
  rigidly now because it's the only way we can be sure that we can
  process multiple documents while rendering headers and footers with
  information corresponding to the appropriate document.  (man(7)'s `TH`
  has an advantage here in that calling it is "atomic": from its
  arguments alone you can obtain everything you need to know to format
  the header and footer.  In mdoc(7), permuting the initialization macro
  order reliably produces chaos.)  Break the page (if necessary)
  _before_ processing any arguments (instead of after), to flush the
  previous page's footer.  Stop calling `doc-set-up-titles` here; we
  don't have enough information to do that yet.  Also stop writing the
  PDF bookmark here, because `doc-document-title` and `doc-section` will
  not reflect the new page content yet.

  (Os): Once the `doc-operating-system` string content has been
  determined, call `doc-set-up-titles`, write the PDF bookmark for the
  page, and call `doc-header`, causing the page header to be formatted.
  These changes further imply a stronger requirement on initialization
  macro ordering being canonical.

Fixes <https://savannah.gnu.org/bugs/?62774> (7/7).

1 files changed, 61 insertions, 12 deletions

diff --git a/tmac/mdoc/doc-common b/tmac/mdoc/doc-common
index 98e21fb5e..2f60d26e8 100644
--- a/tmac/mdoc/doc-common
+++ b/tmac/mdoc/doc-common
@@ -192,6 +192,45 @@
 .nr doc-punct! 3
 .
 .
+.\" Define alternate requests to handle continuous rendering.
+.\"
+.\" This .ne replacement avoids page breaks; instead, the page length is
+.\" increased to the necessary amount (this is needed for tables).
+.
+.eo
+.de doc-ne
+.  ie \n[.$] .nr doc-amount (v;\$*)
+.  el        .nr doc-amount 1v
+.  if (\n[doc-amount] >= \n[.t]) \
+.    pl +(\n[doc-amount]u - \n[.t]u + 1v)
+.  rr doc-amount
+..
+.ec
+.
+.\" This .bp replacement for continuous rendering mode adjusts the page
+.\" length to the current position so that no empty lines are inserted.
+.
+.eo
+.de doc-bp
+.  pl \n[nl]u
+..
+.ec
+.
+.
+.\" NS doc-set-up-continuous-rendering
+.\"   Move macros into place for continuous rendering.  An end-of-input
+.\"   macro is set up by doc-set-up-titles.
+.de doc-set-up-continuous-rendering
+.  rn ne doc-real-ne
+.  rn bp doc-real-bp
+.  rn doc-ne ne
+.  rn doc-bp bp
+..
+.
+.if \n[cR] \
+.  doc-set-up-continuous-rendering
+.
+.
 .\" header assembly macros
 .
 .\" NS doc-document-title global string
@@ -265,6 +304,21 @@
 .
 .eo
 .de Dd
+.  \" If batch processing (rendering multiple) man page documents, we
+.  \" must handle the end of a previous document.
+.  \"
+.  \" If also continuously rendering, cause a page transition to a new
+.  \" mdoc(7) document.  Clear the page header trap first so it is not
+.  \" sprung with stale information.
+.  if !\n[doc-is-first-page-of-document] \{\
+.    ie \n[cR] .doc-end-macro
+.    el \{\
+.      ch doc-header
+.      bp 1
+.    \}
+.    nr doc-is-first-page-of-document 1
+.  \}
+.
 .  if !\n[.$] \
 .    tm mdoc warning: .Dd directive expects an argument (#\n[.c])
 .  if \n[.$] \{\
@@ -446,14 +500,6 @@
 .  if !"\$3"" \
 .    if "\*[doc-volume]"LOCAL" \
 .      ds doc-volume \$3
-.
-.  doc-set-up-titles
-.
-.  if \n[nl] \
-.    bp
-.
-.  if '\*[.T]'pdf' \
-.    pdfbookmark 1 "\*[doc-document-title](\*[doc-section])"
 ..
 .ec
 .
@@ -944,10 +990,13 @@
 .      as doc-operating-system " \$2
 .  \}\}\}\}\}\}\}\}
 .
-.  if \n[doc-is-first-page-of-document] \{\
-.    doc-header
-.    nr doc-is-first-page-of-document 0
-.  \}
+.  doc-set-up-titles
+.
+.  if '\*[.T]'pdf' \
+.    pdfbookmark 1 "\*[doc-document-title](\*[doc-section])"
+.
+.  doc-header
+.  nr doc-is-first-page-of-document 0
 ..
 .ec
 .