From 9365fec1a278974b4cabc9192f0797fc5d1d1682 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?John=20Ankarstr=C3=B6m?= <john@ankarstrom.se>
Date: Fri, 18 Jun 2021 10:40:06 +0200
Subject: g.tmac: Add c (code) macro, rework margins

---
 example.t |  51 +++++++++++++++++++++++------
 g.tmac    | 108 +++++++++++++++++++++++++++++++++++++++++++-------------------
 2 files changed, 118 insertions(+), 41 deletions(-)

diff --git a/example.t b/example.t
index 3ca19bb..1ea01b1 100644
--- a/example.t
+++ b/example.t
@@ -1,26 +1,26 @@
 .so g.tmac
-.s
+.p
+.ta 3n +3n +3n +3n
 .t
 .x Mg ,
 a simple macro package for troff
 .n
 John Ankarstr\[u00F6]m
 .d
+.h
+Introduction
 .p
 .i Mg
 is a simple macro package for troff with the following features:
 .p
-1.
-It is designed to be easy to understand and to customize
+1.	It is designed to be easy to understand and to customize
 by editing the source code.
 .p
-2.
-It makes use of the extended support for environments
+2.	It makes use of the extended support for environments
 offered by many modern troff implementations
 (but it can be made compatible with the original troff if need be).
 .p
-3.
-It is designed to be practically easy to use.
+3.	It is designed to be practically easy to use.
 Macros are consistently one letter long and written in lowercase.
 .p
 While
@@ -33,7 +33,7 @@ Users of
 .i mg
 are encouraged to modify the source code
 according to their own needs.
-.h
+.s
 Internal design
 .p
 .i Mg
@@ -52,4 +52,37 @@ simply sets the font size inside the environment named
 If the user wishes to modify the default font size,
 he or she can simply switch to the
 .i p
-environment and set the font size as desired.
+environment and set the font size as desired:
+.c
+.eo
+.cc ,
+.\" set heading font
+.h
+.fam H
+.ps +1p
+,cc
+.ec
+.p
+The environments are initialized
+as soon as the first
+.q block-level
+macro is called.
+At the initialization of each environment,
+the default environment (0) is copied,
+meaning that all environment-relevant settings
+defined before the first macro call
+are applied to all
+.i mg
+environments.
+It is thus remarkably simple and intuitive to set,
+for example, the default font of a document:
+.c
+.cc ,
+.fam N
+.t
+Document title
+.p
+First paragraph.
+,cc
+.p
+\&...
diff --git a/g.tmac b/g.tmac
index 9f80429..d995c03 100644
--- a/g.tmac
+++ b/g.tmac
@@ -1,6 +1,6 @@
 .eo
 .\" s -- setup document
-.de s
+.de _s
 . \" configure initial options
 . _nr mt 1i	\" margin top
 . _nr mb 1i	\" margin bottom
@@ -11,23 +11,41 @@
 . ns
 . \" configure environments
 . _e t		\" title
+.  evc 0
 .  ps +4p
 .  vs +2p
 .  ft B
 .  ad c
 . _e n		\" name (of author)
-.  _nr n_mt 0.4v
+.  evc 0
+.  nr sp 0.4v
 .  ad c
 . _e d		\" date
-.  _nr d_mt 0.4v
+.  evc 0
+.  nr sp 0.4v
 .  ad c
-. _e p		\" paragraph
-.  _nr p_mt 0.3v
-.  ad b
 . _e h		\" heading
-.  _nr h_mt 0.6v
+.  evc 0
+.  nr sp 0.6v
 .  ps +1p
 .  ft B
+. _e s		\" section heading
+.  evc 0
+.  nr sp 0.6v
+.  ft B
+. _e p		\" paragraph
+.  evc 0
+.  nr sp 0.3v
+.  nr ti 0.5c
+.  ad b
+. _e c		\" code listing
+.  evc 0
+.  nr sp 0.3v
+.  nr in 0.5c
+.  nf
+.  in 0.5c
+.  fam C
+.  ps -1p
 . _e
 ..
 .\" _h -- page header
@@ -46,11 +64,36 @@
 ..
 .\" _e -- set environment
 .de _e
+. if '\n(_s'0' \{\
+.  nr _s 1
+.  _s
+. \}
 . br
-. if !'\n[.ev]'0' .ev
+. if !'\n[.ev]'0' \{\
+.  nr \n[.ev]_sp \n(sp
+.  nr \n[.ev]_in \n(in
+.  nr \n[.ev]_ti \n(ti
+.  ev
+. \}
 . ds penv \*[env]
 . ds env \$1
-. if !'\$1'' .ev \$1
+. if !'\$1'' \{\
+.  ev \$1
+.  nr sp \n[\n[.ev]_sp]
+.  nr in \n[\n[.ev]_in]
+.  nr ti \n[\n[.ev]_ti]
+.  sp \n(spu
+.  in \n(inu
+. \}
+. _mb
+..
+.\" _mb -- margin bottom
+.de _mb
+. ie '\*[env]'n' .return
+. el .if '\*[env]'d' .return
+. ie '\*[penv]'t' .sp 1v
+. el .ie '\*[penv]'n' .sp 1v
+. el .if '\*[penv]'d' .sp 1v
 ..
 .\" i -- italic
 .de i
@@ -60,44 +103,45 @@
 .de x
 \$3\f(BI\$1\fP\$2
 ..
+.\" q -- quote
+.de q
+\$3\(lq\$1\(rq\$2
+..
 .\" t -- title
 .de t
 . _e t
 ..
 .\" n -- name (of author)
 .de n
-.  br
 . _e n
-.  if '\*[penv]'t' .sp 0.2v
-.  sp \n[n_mt]u
+. if '\*[penv]'t' .sp 0.2v
 ..
 .\" d -- date
 .de d
-.  br
 . _e d
-.  if '\*[penv]'t' .sp 0.2v
-.  sp \n[d_mt]u
-.  af mo 00
-.  af dy 00
-.  ie '\$1'' \n[year]-\n(mo-\n(dy
-.  el \$1
-.  af mo 1
-.  af dy 1
+. if '\*[penv]'t' .sp 0.2v
+. af mo 00
+. af dy 00
+. ie '\$1'' \n[year]-\n(mo-\n(dy
+. el \$1
+. af mo 1
+. af dy 1
+..
+.\" h -- heading
+.de h
+. _e h
+..
+.\" s -- section heading
+.de s
+. _e s
 ..
 .\" p -- paragraph
 .de p
-.  br
 . _e p
-.  ie '\*[penv]'t' .sp 1v
-.  el .ie '\*[penv]'n' .sp 1v
-.  el .ie '\*[penv]'d' .sp 1v
-.  el .sp \n[p_mt]u
-.  if '\*[penv]'p' \h'0.5c'
+. if '\*[penv]'p' .ti \n(tiu
 ..
-.\" h -- heading
-.de h
-.  br
-. _e h
-.  sp \n[h_mt]u
+.\" c -- code listing
+.de c
+. _e c
 ..
 .ec
-- 
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