[groff] 06/11: [man]: Ignore FT register when appropriate.

[G. Branden Robinson]

gbranden pushed a commit to branch master
in repository groff.

commit 5a76dfb9c87f6dabc61c6d88e6a5ae616eb05347
Author: G. Branden Robinson <g.branden.robinson@gmail.com>
AuthorDate: Mon May 17 18:52:53 2021 +1000

    [man]: Ignore FT register when appropriate.
    
    * tmac/an-old.tmac (initialization): Validate user-specified value of
      \n[FT].  Continuous rendering ignores FT (page location traps are not
      used for footers in that mode).  Measuring a footer distance from the
      page top isn't done.  A footer distance of over half the page length
      is unlikely.  A footer distance of less than one line height is too.
      Issue diagnostics in all of these cases.
    
    Fixes <https://savannah.gnu.org/bugs/index.php?60612>.
---
 ChangeLog        | 12 ++++++++++++
 tmac/an-old.tmac | 37 +++++++++++++++++++++++++++++++++----
 2 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 69bb36a..5971c8b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,9 +1,21 @@
 2021-05-17  G. Branden Robinson <g.branden.robinson@gmail.com>
 
+       [man]: Ignore FT register when appropriate.
+
+       * tmac/an-old.tmac (initialization): Validate user-specified
+       value of \n[FT].  Continuous rendering ignores FT (page location
+       traps are not used for footers in that mode).  Measuring a
+       footer distance from the page top isn't done.  A footer distance
+       of over half the page length is unlikely.  A footer distance of
+       less than one line height is too.  Issue diagnostics in all of
+       these cases.
+
        * tmac/tests/tmac/tests/\
        an-old_FT-bad-value-should-not-trash-titles.sh: Test it.
        * tmac/tmac.am (tmac_TESTS): Run test.
 
+       Fixes <https://savannah.gnu.org/bugs/index.php?60612>.
+
 2021-05-17  G. Branden Robinson <g.branden.robinson@gmail.com>
 
        * tmac/an-old.tmac (TH): Plant the an-footer trap (where we
diff --git a/tmac/an-old.tmac b/tmac/an-old.tmac
index 56ada26..1a9ccb0 100644
--- a/tmac/an-old.tmac
+++ b/tmac/an-old.tmac
@@ -226,9 +226,11 @@
 .    an-header
 .
 .  if !\\n[cR] \{\
+.    ie r FT .nr an-footer-location \\n[FT]
+.    el      .nr an-footer-location (-.5i)
 .    wh 0 an-header
-.    wh (2u * \\n[FT]u) an-footer
-.    wh \\n[FT]u an-p-footer
+.    wh (2u * \\n[an-footer-location]u) an-footer
+.    wh \\n[an-footer-location]u an-p-footer
 .    \}
 .  \}
 .
@@ -772,8 +774,35 @@
 .    \}
 .
 .\" footer distance
-.if !r FT \
-.  nr FT (-.5i)
+.\"
+.\" Unlike most of these parameters, we do not set a default for FT; the
+.\" TH macro places page location traps only if not continuously
+.\" rendering.
+.\"
+.if r FT \{\
+.  \" Validate it. Continuous rendering ignores FT.  Measuring a footer
+.  \" distance from the page top isn't done.  A footer distance of over
+.  \" half the page length is unlikely.  A footer distance of less than
+.  \" one line height is too.
+.  ie \n[cR] \
+.    ds an-msg footer distance when continuously rendering\"
+.  el \{\
+.    ie (\n[FT] : (\n[FT] = 0)) \
+.      ds an-msg non-negative footer distance: \n[FT]u\"
+.    el \{\
+.      ie (-(\n[FT]) > (\n[.p] / 2)) \
+.        ds an-msg implausibly large footer distance: \n[FT]u\"
+.      el \
+.        if ((v;\n[FT]) < 1v) \
+.          ds an-msg implausibly small footer distance: \n[FT]u\"
+.    \}
+.  \}
+.  if d an-msg \{\
+.    tm \*[an-old]: ignoring \*[an-msg]
+.    rr FT
+.    rm an-msg
+.  \}
+.\}
 .
 .\" hyphenation mode
 .if !r HY \{\