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Path: utzoo!watmath!idallen
From: idallen@watmath.UUCP
Newsgroups: net.wanted.sources,net.text
Subject: Re: Orphans & Widows Fix for Troff Wanted
Message-ID: <2434@watmath.UUCP>
Date: Mon, 5-May-86 02:10:00 EDT
Article-I.D.: watmath.2434
Posted: Mon May  5 02:10:00 1986
Date-Received: Tue, 6-May-86 04:23:02 EDT
References: <312@garth.UUCP> <2331@phri.UUCP>
Reply-To: idallen@watmath.UUCP (Ian! D. Allen)
Distribution: net
Organization: U of Waterloo, Ontario
Lines: 51
Keywords: orphans widows ditroff
Xref: watmath net.wanted.sources:2271 net.text:1060

I know of no cheap way to eliminate those stray lines at the tops of
pages, but a simple addition to your local macro package can at least
tell you about most pages on which they occur.  Most macro packages
have an internal "reset-parameters" macro that does a break then resets
various format things.  Modify this macro so that after the break it
checks to see where you are on the current page.  If you are exactly
one line down from the top of the text portion of the page, you've just
generated a widowed line, and you can .tm this to the user.  The user
can do a dry run of the document without printing it to get a list of
the problem pages, then go back and edit text on the previous pages to
remove the problem areas.

For the -ms macros, the modification might read something like this.
You have to add some complications to allow the SH/NH title macros to put
one-line titles at page top without complaint, and the easiest thing to
do is to catch widows at paragraph end only.

Add this line to the end of the LP macro; add it to PP and IP too if necessary:

	.nr WI \\n%

Add this line to the end of the SH macro; add it to NH too if necessary:

	.nr SH 1

Define an "error message" macro of some sort, such as:

	.de ER
	.tm MS MACROS: Input line \\n(.c: \\$1
	.if \\n(.$>1 .tm ... \\$2
	.if \\n(.$>2 .tm ... \\$3
	.if \\n(.$>3 .tm ... \\$4
	.if \\n(.$>4 .tm ... \\$5
	.if \\n(.$>5 .tm ... \\$6
	.if \\n(.$>6 .tm ... \\$7
	.if \\n(.$>7 .tm ... \\$8
	..

Put this at the beginning of the RT macro:

	.br
	.if \\n(WI&(\\n(SH=0) .if \\n(.z \{\
	.	if (\\n(.h>\\n(HM)&(\\n(WI<\\n%)&(\\n(.h<(\\n(HM+1.2v)) .ER \
	"Possible single line widow at top of page '\\n(PN'"
	.	nr WI 0
	.\}
	.nr SH 0

\n(HM is the -ms register containing the size of the top margin.
-- 
        -IAN!  (Ian! D. Allen)      University of Waterloo