Radical cleanup of COMPATIBILITY sections:

Remove lots of lies, dozens of irrelevant implementation details,
and all references to groff versions older than 1.17.  Move relevant
information to the pages where it belongs, and out of mandoc(1) in
particular.  Add some missing general remarks to roff(7), where it
fits the character and purpose of the page much better.

1 files changed, 8 insertions, 107 deletions

diff --git a/mandoc.1 b/mandoc.1
index cef67da2..275e35dd 100644
--- a/mandoc.1
+++ b/mandoc.1
@@ -321,9 +321,6 @@ Emboldened characters are rendered as
 The special characters documented in
 .Xr mandoc_char 7
 are rendered best-effort in an ASCII equivalent.
-If no equivalent is found,
-.Sq \&?
-is used instead.
 .Pp
 Output width is limited to 78 visible columns unless literal input lines
 exceed this limit.
@@ -344,7 +341,7 @@ for example overfull lines or ugly line breaks.
 .It Cm width Ns = Ns Ar width
 The output width is set to
 .Ar width ,
-which will normalise to \(>=60.
+which will normalise to \(>=58.
 .El
 .Ss HTML Output
 Output produced by
@@ -1670,88 +1667,9 @@ macro or of an undefined macro.
 The macro is ignored, and its arguments are handled
 as if they were a text line.
 .El
-.Sh COMPATIBILITY
-This section summarises
-.Nm
-compatibility with GNU troff.
-Each input and output format is separately noted.
-.Ss ASCII Compatibility
-.Bl -bullet -compact
-.It
-Unrenderable unicode codepoints specified with
-.Sq \e[uNNNN]
-escapes are printed as
-.Sq \&?
-in mandoc.
-In GNU troff, these raise an error.
-.It
-The
-.Sq \&Bd \-literal
-and
-.Sq \&Bd \-unfilled
-macros of
-.Xr mdoc 7
-in
-.Fl T Ns Cm ascii
-are synonyms, as are \-filled and \-ragged.
-.It
-In historic GNU troff, the
-.Sq \&Pa
-.Xr mdoc 7
-macro does not underline when scoped under an
-.Sq \&It
-in the FILES section.
-This behaves correctly in
-.Nm .
-.It
-A list or display following the
-.Sq \&Ss
-.Xr mdoc 7
-macro in
-.Fl T Ns Cm ascii
-does not assert a prior vertical break, just as it doesn't with
-.Sq \&Sh .
-.It
-The
-.Sq \&na
-.Xr man 7
-macro in
-.Fl T Ns Cm ascii
-has no effect.
-.It
-Words aren't hyphenated.
-.El
-.Ss HTML Compatibility
-.Bl -bullet -compact
-.It
-The
-.Sq \efP
-escape will revert the font to the previous
-.Sq \ef
-escape, not to the last rendered decoration, which is now dictated by
-CSS instead of hard-coded.
-It also will not span past the current scope,
-for the same reason.
-Note that in
-.Sx ASCII Output
-mode, this will work fine.
-.It
-The
-.Xr mdoc 7
-.Sq \&Bl \-hang
-and
-.Sq \&Bl \-tag
-list types render similarly (no break following overreached left-hand
-side) due to the expressive constraints of HTML.
-.It
-The
-.Xr man 7
-.Sq IP
-and
-.Sq TP
-lists render similarly.
-.El
 .Sh SEE ALSO
+.Xr apropos 1 ,
+.Xr man 1 ,
 .Xr eqn 7 ,
 .Xr man 7 ,
 .Xr mandoc_char 7 ,
@@ -1762,32 +1680,15 @@ lists render similarly.
 The
 .Nm
 utility was written by
-.An Kristaps Dzonsons Aq Mt kristaps@bsd.lv .
-.Sh CAVEATS
+.An Kristaps Dzonsons Aq Mt kristaps@bsd.lv
+and is maintained by
+.An Ingo Schwarze Aq Mt schwarze@openbsd.org .
+.Sh BUGS
 In
-.Fl T Ns Cm html
-and
-.Fl T Ns Cm xhtml ,
+.Fl T Ns Cm html ,
 the maximum size of an element attribute is determined by
 .Dv BUFSIZ ,
 which is usually 1024 bytes.
 Be aware of this when setting long link
 formats such as
 .Fl O Ns Cm style Ns = Ns Ar really/long/link .
-.Pp
-Nesting elements within next-line element scopes of
-.Fl m Ns Cm an ,
-such as
-.Sq br
-within an empty
-.Sq B ,
-will confuse
-.Fl T Ns Cm html
-and
-.Fl T Ns Cm xhtml
-and cause them to forget the formatting of the prior next-line scope.
-.Pp
-The
-.Sq \(aq
-control character is an alias for the standard macro control character
-and does not emit a line-break as stipulated in GNU troff.