[tbl]: Fix Savannah #63640 and #63749.

[tbl]: Fix bugs using boxes or vertical rules at table edges on nroff
devices, particularly when combined with region or column expansion.

* src/preproc/tbl/table.h (class table): Add `GAP_EXPAND` enumeration
  constant.  James Clark seems to have designed GNU tbl carefully to
  avoid distinguishing region expansion from column expansion in a
  categorical way, but I needed a way for formatting-time logic to know
  which was in use.  (Column expansion, the "x" modifier, expands
  columns--i.e., text.  Region expansion expands [or compresses] the
  _gaps_ between columns.)

* src/preproc/tbl/main.cpp (process_options): Set `GAP_EXPAND` flag in
  table if "expand" region option seen.

* src/preproc/tbl/table.cpp: Add new macro `LEFTOVER_FACTOR_REG` to name
  a new roff register for the remainder of gap-expansion space when the
  amount of space available for expansion is divided by the number of
  gaps.

  (table::compute_overall_width): If _not_ expanding a table in
  either respect and in nroff mode, reduce line length by 1n for each of
  any left and right border (because the vertical lines eat character
  cells).  This prevents bordered or boxed tables from being overset
  even when they use neither expansion feature.

  (table::compute_separation_factor): If gap-expanding a table, store
  any remainder from the division used to compute the separation factor
  into the new `LEFTOVER_FACTOR_REG`.

  (table::compute_column_positions): Insert that remainder into the gap
  before the last (rightmost) column of the table.  This _could_ be done
  more elegantly by spreading each en in a symmetric way across a subset
  of the gaps.  (It is necessarily a subset by the pigeonhole
  principle.)  But it didn't seem worth the effort for a feature (region
  expansion) that few users employ.  (Usually what you want is the "x"
  column modifier.)  Alternatively, "forget it, Jake--it's a terminal
  emulator".

* src/preproc/tbl/tbl.am (tbl_XFAIL_TESTS): Remove now-passing tests.

Fixes <https://savannah.gnu.org/bugs/?63640> and
<https://savannah.gnu.org/bugs/?63749>.

1 files changed, 43 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 4ac8a3fe9..ecae94519 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,48 @@
 2023-02-03  G. Branden Robinson <g.branden.robinson@gmail.com>
 
+	[tbl]: Fix bugs using boxes or vertical rules at table edges on
+	nroff devices, particularly when combined with region or column
+	expansion.
+
+	* src/preproc/tbl/table.h (class table): Add `GAP_EXPAND`
+	enumeration constant.  James Clark seems to have designed GNU
+	tbl carefully to avoid distinguishing region expansion from
+	column expansion in a categorical way, but I needed a way for
+	formatting-time logic to know which was in use.  (Column
+	expansion, the "x" modifier, expands columns--i.e., text.
+	Region expansion expands [or compresses] the _gaps_ between
+	columns.)
+	* src/preproc/tbl/main.cpp (process_options): Set `GAP_EXPAND`
+	flag in table if "expand" region option seen.
+	* src/preproc/tbl/table.cpp: Add new macro `LEFTOVER_FACTOR_REG`
+	to name a new roff register for the remainder of gap-expansion
+	space when the amount of space available for expansion is
+	divided by the number of gaps.
+	(table::compute_overall_width): If _not_ expanding a table in
+	either respect and in nroff mode, reduce line length by 1n for
+	each of any left and right border (because the vertical lines
+	eat character cells).  This prevents bordered or boxed tables
+	from being overset even when they use neither expansion feature.
+	(table::compute_separation_factor): If gap-expanding a table,
+	store any remainder from the division used to compute the
+	separation factor into the new `LEFTOVER_FACTOR_REG`.
+	(table::compute_column_positions): Insert that remainder into
+	the gap before the last (rightmost) column of the table.  This
+	_could_ be done more elegantly by spreading each en in a
+	symmetric way across a subset of the gaps.  (It is necessarily a
+	subset by the pigeonhole principle.)  But it didn't seem worth
+	the effort for a feature (region expansion) that few users
+	employ.  (Usually what you want is the "x" column modifier.)
+	Alternatively, "forget it, Jake--it's a terminal emulator".
+
+	* src/preproc/tbl/tbl.am (tbl_XFAIL_TESTS): Remove now-passing
+	tests.
+
+	Fixes <https://savannah.gnu.org/bugs/?63640> and
+	<https://savannah.gnu.org/bugs/?63749>.
+
+2023-02-03  G. Branden Robinson <g.branden.robinson@gmail.com>
+
 	* src/preproc/tbl/table.cpp (table::compute_column_positions):
 	Stop multiplying the gaps at the left and right edges of a table
 	{which occur when it is boxed or has a leading and/or trailing