page.tmac

\# -*- nroff -*-
\########################################################################
\################## Module pg - Margins and page layout #################
\########################################################################


\########################### External variables #########################
.Number pg*margin-top 1i
.Number pg*padding-top 2v
.Number pg*margin-bottom 1i
.Number pg*padding-bottom 1v
.Number pg*margin-left 1i
.Number pg*margin-right 1i
.Number pg*line-length (\n[si*width] - \n[pg*margin-left] - \n[pg*margin-right])


\########################### Internal variables #########################
.Number @pg*page-broken 0
.Number @pg*margins-set 0
.String @pg*header ||||
.String @pg*footer ||- % -||

\############################ Internal macros ###########################


\############################ External macros ###########################

.de NewPage
\# Can be invoked multiple times per page, breaking the page and ensuring
\#   this happens only once per page.
.  nr @pg*page-broken +1
.  if (\\n[@pg*page-broken] = 1) \{\
.    bp
\#.    nop \\h"|(u;\\n[pg*margin-bottom]u-1u)u"
.  \}
..

\# Margin setter macros
\#TODO: possibly check whether .Start was invoked or not, and if it was
\#  set the margins straight away (even if changing margins partway the
\#  document is probably one of the things that Shouldn't Be Done™).

.de PaddingTop
.  nr pg*padding-top \\$1
..

.de PaddingBottom
.  nr pg*padding-bottom \\$1
..

.de MarginTop
.  nr @pg*margins-set +1
.  nr pg*margin-top \\$1
..

.de MarginBottom
.  nr @pg*margins-set +1
.  nr pg*margin-bottom \\$1
..

.de MarginLeft
.  nr @pg*margins-set +1
.  nr pg*margin-left \\$1
..

.de MarginRight
.  nr @pg-margins-set +1
.  nr pg*margin-right \\$1
..

.de @pg*SetMargins
.  MarginTop \\$1
.  MarginBottom \\$2
.  MarginLeft \\$3
.  MarginRight \\$4
..

.de Margins
.  if (\\n[.$] = 1) .@pg*SetMargins \\$1 \\$1 \\$1 \\$1
.  if (\\n[.$] = 2) .@pg*SetMargins \\$1 \\$1 \\$2 \\$2
.  if (\\n[.$] = 4) .@pg*SetMargins \\$1 \\$2 \\$3 \\$4
..

\# Header & footer macros

.de @pg*SetupEnv
.  po \\n[pg*margin-left]u
.  ll \\n[pg*line-length]u
.  lt \\n[pg*line-length]u
..

.de Header
.  ds @pg*header \\$*
..

.de @pg*Header
.  nr @pg*page-broken 0
.  sp (u;\\n[pg*margin-top]u - \\n[pg*padding-top]u - 1v)
.  ev @pg*header-env
.    @pg*SetupEnv
.    tl \\*[@pg*header]
.  ev
.  sp \\n[pg*padding-top]u
..

.de Footer
.  ds @pg*footer \\$*
..

.de @pg*Footer
.  tm Footer reached on page \\n[%]
.  sp \\n[pg*padding-bottom]u
.  ev @pg*footer-env
.    @pg*SetupEnv
.    tl \\*[@pg*footer]
\#.    sp (u;\\n[pg*margin-bottom]u - \\n[pg*padding-bottom]u - 1v)
.  ev
.  bp
..

\# Macros to actually modify the page and set the various traps

.de @pg*MarginTop
.  wh 0 @pg*Header
..

.de @pg*MarginBottom
.  wh -(u;\\n[pg*margin-bottom]) @pg*Footer
..

.de @pg*MarginLeft
.  po \\n[pg*margin-left]u
.  ll -\\n[pg*margin-left]u
.  lt -\\n[pg*margin-left]u
.  nr pg*line-length \\n[.l]
..

.de @pg*MarginRight
.  ll -\\n[pg*margin-right]u
.  lt -\\n[pg*margin-right]u
.  nr pg*line-length \\n[.l]
..

\# Initialization macro

.de @pg*Init
.  @pg*MarginTop
.  @pg*MarginBottom
.  @pg*MarginLeft
.  @pg*MarginRight
..