@Section
   @Title { Paragraph breaking }
   @Tag { paras }
@Begin
@PP
@I { Paragraph breaking } is the process of
paragraph.breaking @Index { paragraph breaking }
inserting line breaks into paragraphs at places appropriate to the column
width.  Lout works out suitable column widths and performs paragraph
breaking automatically, finding an `optimal' break with the method
used by the @TeX
tex.paragraph @SubIndex { paragraph breaking }
system.  It offers ten styles of paragraph breaking,
which we will explore with the aid of this example:
@ID @OneRow @Code {
It is a truth universally
acknowledged, that a single man
in possession of a good fortune,
must be in want of a wife.
}
Changing the paragraph breaking style is similar to changing the font,
colour, or language, and is done using the @Code "@Break" symbol:
breakzzz.sym @Index { @Code "@Break" symbol }
@ID @Code "ragged @Break ..."
This example causes every paragraph in the following object to be
broken using the @Code ragged style, of which more below.
@PP
The first two styles perform @I { line adjustment }, which
line.adjustment @Index { line adjustment }
means that they enlarge the spaces between the objects making up each
line except the last so as to fill the lines completely:
@IndentedList
@LI @Tab
    @Fmta { @Col 6c @Wide @Code A ! @Col 7c @Wide B }
{
@Rowa
    A { "adjust @Break ..." }
    B { adjust @Break {
It is a truth universally
acknowledged, that a single man
in possession of a good fortune,
must be in want of a wife.
}}
}
@LI @Tab
    @Fmta { @Col 6c @Wide @Code A ! @Col 7c @Wide B }
{
@Rowa
    A { "outdent @Break ..." }
    B { outdent @Break {
It is a truth universally
acknowledged, that a single man
in possession of a good fortune,
must be in want of a wife.
}}
}
@EndList
The @Code adjust style is frequently used, so it has been chosen as the
default style.  Outdenting adds a small space at the start of each line
outdent. @Index { outdented paragraphs }
except the first, and is much less common.
@PP
The next four styles do not adjust lines, leaving the paragraph
ragged. @Index { @Code ragged paragraph breaking style }
cragged. @Index { @Code cragged paragraph breaking style }
rragged. @Index { @Code rragged paragraph breaking style }
oragged. @Index { @Code oragged paragraph breaking style }
{@I ragged}:
@IndentedList
@LI @Tab
    @Fmta { @Col 6c @Wide @Code A ! @Col 7c @Wide B }
{
@Rowa
    A { "ragged @Break ..." }
    B { ragged @Break {
It is a truth universally
acknowledged, that a single man
in possession of a good fortune,
must be in want of a wife.
}}
}
@LI @Tab
    @Fmta { @Col 6c @Wide @Code A ! @Col 7c @Wide B }
{
@Rowa
    A { "cragged @Break ..." }
    B { cragged @Break {
It is a truth universally
acknowledged, that a single man
in possession of a good fortune,
must be in want of a wife.
}}
}
@LI @Tab
    @Fmta { @Col 6c @Wide @Code A ! @Col 7c @Wide B }
{
@Rowa
    A { "rragged @Break ..." }
    B { rragged @Break {
It is a truth universally
acknowledged, that a single man
in possession of a good fortune,
must be in want of a wife.
}}
}
@LI @Tab
    @Fmta { @Col 6c @Wide @Code A ! @Col 7c @Wide B }
{
@Rowa
    A { "oragged @Break ..." }
    B { oragged @Break {
It is a truth universally
acknowledged, that a single man
in possession of a good fortune,
must be in want of a wife.
}}
}
@EndList
The paragraph is broken in the same places as @Code adjust breaks it,
but the resulting lines are left-justified, centred, or right-justified
with respect to each other, rather than adjusted; @Code "oragged"
is like @Code "outdent" except the resulting lines are not adjusted.
@PP
If you have a few words that must be kept together on one line, the
preventing. @Index { preventing line breaks }
keeping. @Index { keeping things on one line }
recommended way is to separate them by the @Code "~" symbol:
@ID @Code "According to Prof.~Jones, the effect of ..."
It's best not to bother about this until you actually get a bad line
break, since chances are good that the words will fall on one line anyway.
@PP
The last four styles differ from the first six in breaking the
paragraph at the points where it is broken in the original input:
lines. @Index { @Code lines paragraph breaking style }
clines. @Index { @Code clines paragraph breaking style }
olines. @Index { @Code olines paragraph breaking style }
rlines. @Index { @Code rlines paragraph breaking style }
@IndentedList
@LI @Tab
    @Fmta { @Col 6c @Wide @Code A ! @Col 7c @Wide B }
{
@Rowa
    A { "lines @Break ..." }
    B { lines @Break {
It is a truth universally
acknowledged, that a single man
in possession of a good fortune,
must be in want of a wife.
}}
}
@LI @Tab
    @Fmta { @Col 6c @Wide @Code A ! @Col 7c @Wide B }
{
@Rowa
    A { "clines @Break ..." }
    B { clines @Break {
It @PageMark clines is a truth universally
acknowledged, that a single man
in possession of a good fortune,
must be in want of a wife.
}}
}
@LI @Tab
    @Fmta { @Col 6c @Wide @Code A ! @Col 7c @Wide B }
{
@Rowa
    A { "rlines @Break ..." }
    B { rlines @Break {
It is a truth universally
acknowledged, that a single man
in possession of a good fortune,
must be in want of a wife.
}}
}
@LI @Tab
    @Fmta { @Col 6c @Wide @Code A ! @Col 7c @Wide B }
{
@Rowa
    A { "olines @Break ..." }
    B { olines @Break {
It is a truth universally
acknowledged, that a single man
in possession of a good fortune,
must be in want of a wife.
}}
}
@EndList
The lines are left-justified, centred, right-justified, or outdented
with respect to each other in the same way as for the ragged styles.
@PP
When using the @Code lines style, there are some fine points concerning
the proper use of white space.  Consider this example:
@ID @OneRow @Code {
"@IndentedDisplay lines @Break @I {"
"Teach me to hear Mermaides singing,"
"Or to keep off envies stinging,"
"     And finde"
"     What winde"
"Serves to'advance an honest minde."
"}"
}
The result is the indented display
@IndentedDisplay lines @Break @I {
Teach me to hear Mermaides singing,
Or to keep off envies stinging,
     And finde
     What winde
Serves to'advance an honest minde.
}
This style is the only one for which it is useful to indent individual
input lines; as the result shows, such indents will be respected.
However, Lout's rule that only white space separating objects
affects the result (Section {@NumberOf spaces}) still holds, so
indenting the first line is not effective:
@ID @OneRow @Code {
"@IndentedDisplay lines @Break @I {"
"     And finde"
"     What winde"
"Serves to'advance an honest minde."
"}"
}
produces
@IndentedDisplay lines @Break @I {
     And finde
     What winde
Serves to'advance an honest minde.
}
This may seem awkward, but actually it is very convenient, because
you don't have to worry about whether the first line of the paragraph
should appear on a new line as above, or immediately after the opening
brace:  space at that point does not separate two objects, so it has
no effect.  The indent can be obtained by starting the first line
with an empty object (Section {@NumberOf empty}):
@ID @OneRow @Code {
"@IndentedDisplay lines @Break @I {"
"{}     And finde"
"     What winde"
"Serves to'advance an honest minde."
"}"
}
The result is
@IndentedDisplay lines @Break @I {
{}     And finde
     What winde
Serves to'advance an honest minde.
}
as desired.
@PP
When using {@Code lines}, {@Code clines}, {@Code rlines}, and
{@Code "olines @Break"}, blank lines are respected and ordinarily appear
at their full height.  However, it often looks better to give somewhat
blanklinescale. @Index { @Code blanklinescale }
less than this to blank lines.  For this there is the {@Code blanklinescale}
option to {@Code "@Break"}:
@ID @OneRow @Code @Verbatim {
@IndentedDisplay { lines blanklinescale 0.6 } @Break @I {
Go, and catch a falling star,
     Get with child a mandrake root,
Tell me, where all past years are,
     Or who cleft the Devil's foot,
Teach me to hear Mermaides singing,
Or to keep off envies stinging,
     And finde
     What winde
Serves to'advance an honest minde.

If thou be'st born to strange sights,
     Things invisible to see,
Ride ten thousand days and nights,
     Till age snow white hairs on thee,
Thou, when thou return'st, wilt tell me
All strange wonders that befell thee,
     And swear
     No where
Lives a woman true, and fair.
}
}
As shown, @Code "blanklinescale" may appear at any point in the
object to the left of {@Code "@Break"}, followed by a number
indicating how much to scale the usual height of a blank line by.  The
object to the left of @Code "@Break" has to be enclosed in braces as
shown, to ensure that its extent is clear.  The result is
@IndentedDisplay { lines blanklinescale 0.6 } @Break @I {
Go, and catch a falling star,
     Get with child a mandrake root,
Tell me, where all past years are,
     Or who cleft the Devil's foot,
Teach me to hear Mermaides singing,
Or to keep off envies stinging,
     And finde
     What winde
Serves to'advance an honest minde.

If thou be'st born to strange sights,
     Things invisible to see,
Ride ten thousand days and nights,
     Till age snow white hairs on thee,
Thou, when thou return'st, wilt tell me
All strange wonders that befell thee,
     And swear
     No where
Lives a woman true, and fair.
}
in which the verses are separated by considerably less than a full
blank line; instead of a baseline-to-baseline gap of twice the
interline space, as usual, the gap here is only 1.6 times the
interline space.  Two blank lines would give 2.2 times the
interline space, and so on.  There is no unit of measurement
associated with {@Code "blanklinescale"}, because it is a scale
factor, not a length.
@PP
To set the entire document in a paragraph breaking style other
than {@Code "adjust"}, you need to change the @Code "@InitialBreak" option,
as explained at the end of Section {@NumberOf linespace}.
@PP
Some people don't like to see the first line of a paragraph alone at the
widows @Index { widow lines }
orphans @Index { orphan lines }
unbreakablefirst. @Index { @Code unbreakablefirst }
unbreakablelast. @Index { @Code unbreakablelast }
foot of a page or column (the rest appearing on the next page).  You can
instruct Lout not to allow this with
@ID @Code "unbreakablefirst @Break ..."
meaning that the first line cannot be broken off from the rest of the
paragraph.  Similarly,
@ID @Code "unbreakablelast @Break ..."
instructs Lout to prevent the last line of a paragraph from appearing
alone at the top of a page or column.  These features would probably be
invoked in the @Code "@InitialBreak" option, like this:
@ID
@Code "@InitialBreak { unbreakablefirst unbreakablelast hyphen adjust 1.2fx }"
You can turn them off with @Code "breakablefirst @Break"
and @Code "breakablelast @Break".  In both cases Lout makes it happen by
breaking at the previous place, either between paragraphs or two lines from
the end of a paragraph.  Both features are compatible with Lout's
@Code "@OptimizePages" option, which optimizes the overall page
layout subject to these requirements.
@End @Section
