gbranden pushed a commit to branch master
in repository groff.
commit 7b2bbad6dc0b25f0941d9fdd8b742733b15d1656
Author: G. Branden Robinson <[email protected]>
AuthorDate: Sun Jan 25 20:52:04 2026 -0600
[doc,man]: Revise old ditroff output discussion.
Rename Texinfo node/subsubsection and man page subsection from "Obsolete
command" to "Legacy compressed encoding". Add anchor to keep hyperlinks
to old versions of the manual working.
Revise discussion to reflect the syntax's purpose, as thoroughly treated
by Kernighan's CSTR #97, of which the prior author of this material
seems to have been unaware.
---
doc/groff.texi.in | 47 +++++++++++++++++++++++++++++++++--------------
man/groff_out.5.man | 28 +++++++++++++++++-----------
2 files changed, 50 insertions(+), 25 deletions(-)
diff --git a/doc/groff.texi.in b/doc/groff.texi.in
index bf15cc402..72dfc9038 100644
--- a/doc/groff.texi.in
+++ b/doc/groff.texi.in
@@ -23405,7 +23405,7 @@ GNU
* Simple Commands::
* Graphics Commands::
* Device Control Commands::
-* Obsolete Command::
+* Legacy Compressed Encoding::
@end menu
@node Comment Command
@@ -23924,13 +23924,19 @@ This command is generated by the escape sequence
Line continuation is a GNU extension.
@end table
-@node Obsolete Command
-@subsubsection Obsolete Command
-In @acronym{AT&T} @code{troff} output, the writing of a single glyph is
-mostly done by a very strange command that combines a horizontal move
-and a single character giving the glyph name. It doesn't have a command
-code, but is represented by a 3-character argument consisting of exactly
-2@tie{}digits and a character.
+@anchor{Obsolete Command} @c 1.23.0
+@node Legacy Compressed Encoding
+@subsubsection Legacy Compressed Encoding
+@acronym{AT&T}
+@command{troff}
+output primarily emitted glyphs by writing two digits
+(a motion)
+followed by a single character corresponding to a glyph.
+This syntax is less a command itself than a compressed encoding of the
+@code{c}
+and
+@code{h}
+commands.
@table @asis
@item @var{dd}@var{g}
@@ -23945,12 +23951,25 @@ commands are used, mostly without spaces; this made
such output almost
unreadable.
@end table
-For modern high-resolution devices, this command does not make sense
-because the width of the glyphs can become much larger than two decimal
-digits. In @command{@g@troff}, this is only used for the devices
-@code{X75}, @code{X75-12}, @code{X100}, and @code{X100-12}. For other
-devices, the commands @samp{t} and @samp{u} provide a better
-functionality.
+For modern high-resolution devices,
+this command is impractical
+because the widths of the glyphs have a greater magnitude
+in basic units
+than two decimal digits can represent.
+In
+GNU
+@command{troff}, @c GNU
+this optimization is used only for the devices
+@code{X75},
+@code{X75-12},
+@code{X100},
+and @code{X100-12}.
+For other devices,
+the commands
+@samp{t}
+and
+@samp{u}
+produce more readable output.
@c ---------------------------------------------------------------------
diff --git a/man/groff_out.5.man b/man/groff_out.5.man
index f3542f17e..5c9924783 100644
--- a/man/groff_out.5.man
+++ b/man/groff_out.5.man
@@ -1447,17 +1447,21 @@ Line continuation is a GNU extension.
.
.
.\" ====================================================================
-.SS "Obsolete command"
+.SS "Legacy compressed encoding"
.\" ====================================================================
.
-In
-.I classical troff
-output, emitting a single glyph was mostly done by a very
-strange command that combined a horizontal move and the printing of a
-glyph.
+AT&T}
+.I troff \" AT&T
+output primarily emitted glyphs by writing two digits
+(a motion)
+followed by a single character corresponding to a glyph.
+.
+This syntax is less a command itself than a compressed encoding of the
+.B c
+and
+.B h
+commands.
.
-It didn't have a command code, but is represented by a 3-character
-argument consisting of exactly 2\~digits and a character.
.
.TP
.I ddc
@@ -1490,9 +1494,11 @@ spaces; this made such output almost unreadable.
.
.
.P
-For modern high-resolution devices, this command does not make sense
-because the width of the glyphs can become much larger than two
-decimal digits.
+For modern high-resolution devices,
+this command is impractical
+because the widths of the glyphs have a greater magnitude
+in basic units
+than two decimal digits can represent.
.
In
.IR groff ,
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