@Section
    @Title { Page numbers and running headers }
    @Tag { headers }
@Begin
@PP
A @I { page header } is a line at the top of a page containing a page
page.header @Index { page header }
running.header @Index { running header }
number or running title.  A @I { page footer } is a similar line at
page.footer @Index { page footer }
the bottom of a page.  This section describes the setup file options
that control the appearance of page headers and footers.
@PP
There are four basic styles, selected by the @Code "@PageHeaders" option:
page.headers @Index @Code "@PageHeaders"
@ID @Tab
    @Fmta { @Col @Code { "@PageHeaders {" A "}" } ! @Col B }
{
@Rowa
    A { None }
    B { No page headers, no page footers. }
@Rowa
    A { Simple }
    B { No footers, and a centred page number between hyphens for
header on every page whose number is not 0 or 1. }
@Rowa
    A { Titles }
    B { Full running titles as in the present document. }
@Rowa
    A { NoTitles }
    B { Page numbers placed as for @Code { Titles }, but with the
titles themselves blanked out. }
}
@Code Titles and @Code NoTitles use Lout's cross-referencing machinery,
so will require a few runs to settle down.  @Code None and @Code Simple
do not, so they work first time and may be used with the @Code "-s"
command line flag.  Section {@NumberOf cross} has a fuller discussion
of these ramifications of cross referencing.
@PP
The next step is to set the page numbers, using
the @Code "@PageNumbers" and @Code "@FirstPageNumber" options.  There
page.numbers @Index @Code "@PageNumbers"
are two useful values for {@Code "@PageNumbers"}:
@ID @Tab
    @Fmta { @Col @Code { "@PageNumbers {" A "}" } ! @Col B }
{
@Rowa
    A { Arabic }
    B { Arabic page numbers }
@Rowa
    A { Roman }
    B { Lower-case Roman page numbers }
}
although the full range of choices is {@Code "None"}, {@Code "Arabic"},
{@Code "Roman"}, {@Code "UCRoman"}, {@Code "Alpha"}, and
{@Code "UCAlpha"}.  @Code "@FirstPageNumber" is the number of the
first.page.number @Index @Code "@FirstPageNumber"
first page.  Its default value is of course {@Code 1}, although
@ID @Code "@FirstPageNumber { 0 }"
might be useful if the first page is really an unnumbered cover
sheet.  @Code "@FirstPageNumber" must be an Arabic number even if
@Code "@PageNumbers" is set to something other than {@Code "Arabic"}.
@PP
Some document types, such as books and technical reports with cover
sheets, have a separate introductory
sequence of pages preceding the main sequence.  For the page numbers on
introductory pages there are two options, @Code "@IntroPageNumbers"
intro.page.numbers @Index @Code "@IntroPageNumbers"
intro.first.page.number @Index @Code "@IntroFirstPageNumber"
and {@Code "@IntroFirstPageNumber"}, which are exactly analogous to
@Code "@PageNumbers" and {@Code "@FirstPageNumber"}.  It is traditional
to number introductory pages using Roman numerals, so @Code Roman is
the default value of {@Code "@IntroPageNumbers"}.
@PP
Let's summarize the five options so far by looking at their values in
the @Code book setup file, which was used to produce the present document:
@ID @OneRow @Code {
"@PageHeaders { Titles }"
"@PageNumbers { Arabic }"
"@FirstPageNumber { 1 }"
"@IntroPageNumbers { Roman }"
"@IntroFirstPageNumber { 1 }"
}
The remainder of this section goes beyond these basic choices to explain
how to change the detailed appearance of page headers
and footers.  Inevitably it gets quite a lot harder.
@PP
Pages are classified by the page header options in three ways:
@NumberedList
@LI { @I { Odd vs. even }.  The first page is odd, the second is even,
odd.pages @Index { odd and even pages }
the third is odd, and so on.  If @Code "@FirstPageNumber" is set to
an even number, the first page will have that number, but it will still
be classified as odd. }
@LI { @I { Start vs. non-start }.  A start page is the first page of
start.pages @Index { start and non-start pages }
some major part of the document (a chapter, say); other pages are
non-start.  The @Code { Simple } header type uses a simpler
definition:  a page whose number is 0 or 1 is a start page, all others
are non-start. }
@LI { @I { Intro vs. non-intro }.  Intro pages form a separate sequence of
intro.pages @Index { intro and non-intro pages }
pages that precede the main (non-intro) sequence.  They typically contain
prefatory material such as a title page, preface, and table of contents.
In a book there will always be an even number of Intro pages, even if
it means that the last one is empty. }
@EndList
These classifications are quite independent of each other:  a page
could be a non-intro start odd page, or an intro non-start even page,
and so on.  This makes eight (@Eq { 2 times 2 times 2 }) possibilities
altogether.  Depending on the type of document there may also be pages
that Lout will never place a page header or footer on.  For example, no page
headers or footers will appear on pages containing part titles in books.
@PP
If you choose {@Code "@PageHeaders { None }"}, there are no page headers
or footers, so there is nothing more to say.  If you choose
{@Code "@PageHeaders { Simple }"}, then eight options become relevant
for controlling the page headers on each of the eight kinds of
pages.  Here they are with their default values:
@ID @OneRow @Code {
"@OddTop { @Centre { - @PageNum - } }"
"@EvenTop { @Centre { - @PageNum - } }"
"@StartOddTop { @Null }"
"@StartEvenTop { @Null }"
"@IntroOddTop { @Null }"
"@IntroEvenTop { @Null }"
"@IntroStartOddTop { @Null }"
"@IntroStartEvenTop { @Null }"
}
If the word @Code Start is missing from an option name, the option
applies to non-start pages; if @Code Intro is missing, it applies to
non-intro pages.  Another eight options control footers in the same way:
@ID @OneRow @Code {
"@OddFoot { @Null }"
"@EvenFoot { @Null }"
"@StartOddFoot { @Null }"
"@StartEvenFoot { @Null }"
"@IntroOddFoot { @Centre @PageNum }"
"@IntroEvenFoot { @Null }"
"@IntroStartOddFoot { @Centre @PageNum }"
"@IntroStartEvenFoot { @Null }"
}
The value of the option is an object which becomes the header or
footer.  It may be any object, but there are some peculiarities that
will be explained now.
@PP
The full set of symbols of the BasicSetup package can be used
when setting page header options (and indeed any of the options
of the @Code "@BasicSetup" @Code "@Use" clause package), as well as
symbols from special-purpose
packages that have been included before this setup file.  This means
you can use any symbol you might reasonably expect to.  But footnotes and
floating figures and tables, for example, are not from BasicSetup so
cannot be used.
@PP
There are five symbols of special relevance to page headers and
footers:  {@Code "@Null"}, {@Code "@Centre"}, {@Code "@Center"},
{@Code "@Right"}, and {@Code "@PageNum"}.
@PP
The @Code "@Null" symbol is similar to the empty object in printing as
null. @Index @Code "@Null"
nothing, but in addition it removes the vertical space that ordinarily
separates the header line from the page body.  If there is no header
there should be no vertical space either, so always use @Code "@Null"
rather than the empty object in header and footer options.
@PP
@Code "@Centre" and @Code "@Center" centre the following object, and
centre. @Index @Code "@Centre"
center. @Index @Code "@Center"
right. @Index @Code "@Right"
@Code "@Right" right-justifies it:
@ID @Code "at left  @Centre { - 27 - }  @Right { at right }"
produces
@QD @HExpand { at left  @Centre { - 27 - }  @Right { at right } }
The objects should be enclosed in braces if they contain spaces.
@PP
The @Code "@PageNum" symbol produces the number of the current page, in
page.num. @Index @Code "@PageNum"
Arabic, Roman, etc. as specified by the @Code "@PageNumbers" or
@Code "@IntroPageNumbers" option.  @Code "@PageNum" is available only
within page header and footer options.
@PP
To get the @I last page into a header, so that you can have page
headers like `Page 5 of 8', you need @Code "@NumberOf last.page" as
described in Section {@NumberOf cross}.  You might have
@ID @Code "@Centre { Page @PageNum of @NumberOf last.page }"
as the value of @Code "@EvenTop" and the rest.
@PP
At this point you might like to pause and verify that the default
values of the sixteen options given above produce what we said they
would:  no footers, and a centred page number between hyphens on every
page whose number is not 0 or 1.  It should be clear now what to do if
you want to remove the hyphens, move the numbers to the page footer,
make them bold, have them at the left on even pages and at the right on
odd pages, and so on.
@PP
A different set of sixteen options applies when @Code "@PageHeaders"
is set to @Code Titles or {@Code "NoTitles"}.  Here are the eight
options for headers, with their default values:
@ID @OneRow @Code {
"@RunningOddTop { @I { @MinorNum @DotSep @MinorTitle }"
"       @Right @B @PageNum }"
"@RunningEvenTop { @B @PageNum"
"       @Right @I { @MajorNum @DotSep @MajorTitle } }"
"@RunningStartOddTop { @Null }"
"@RunningStartEvenTop { @Null }"
"@RunningIntroOddTop { @Null }"
"@RunningIntroEvenTop { @Null }"
"@RunningIntroStartOddTop { @Null }"
"@RunningIntroStartEvenTop { @Null }"
}
Some options occupy two lines, but only because they are long:  as
usual, the end of a line is the same as one space.  Here are the
options for footers:
@ID @OneRow @Code {
"@RunningOddFoot { @Null }"
"@RunningEvenFoot { @Null }"
"@RunningStartOddFoot { @Centre { Bold 0.8f } @Font @PageNum }"
"@RunningStartEvenFoot { @Centre { Bold 0.8f } @Font @PageNum }"
"@RunningIntroOddFoot { @Right @PageNum  }"
"@RunningIntroEvenFoot { @PageNum }"
"@RunningIntroStartOddFoot { @Null }"
"@RunningIntroStartEvenFoot { @Null }"
}
All these options are similar to the earlier ones, in providing one
option for each of the eight kinds of pages.  The names are the same
except that @Code Running is added to each.  Remember that a start
page is now one that begins a major part of the document.
@PP
In addition to the symbols described earlier for simple page headers
and footers, these running header options may contain the symbols
{@Code "@MajorNum"}, {@Code "@MajorTitle"}, {@Code "@MinorNum"},
{@Code "@MinorTitle"}, {@Code "@DotSep"}, {@Code "@NoDotSep"},
{@Code "@DotJoin"}, {@Code "@NoDotJoin"}, {@Code "@DashJoin"},
and {@Code "@NumSep"} described below.
major.num @Index @Code "@MajorNum"
major.title @Index @Code "@MajorTitle"
minor.num @Index @Code "@MinorNum"
minor.title @Index @Code "@MinorTitle"
@PP
The exact values of {@Code "@MajorNum"}, {@Code "@MajorTitle"},
{@Code "@MinorNum"}, and {@Code "@MinorTitle"} depend on the document
type, but they are intended to describe what is on the current page.  Here
are some values typical of books:
@ID @Tab
    @Fmta { @Col @Code A ! @Col @Code B }
    vmargin { 0.5vx }
{
@Rowa
    A { "@MajorNum" }
    B { Chapter 2 }
@Rowa
    A { "@MajorTitle" }
    B { Adding Structure to Documents }
@Rowa
    A { "@MinorNum" }
    B { 2.7 }
@Rowa
    A { "@MinorTitle" }
    B { Tables of contents }
}
It is not possible to change the values assigned to these symbols, but
the sixteen options allow you to choose whether to use them and how to
arrange them, in the usual way.
@PP
The @Code "@DotSep" symbol consumes the objects to its left and right
dot.sep @Index @Code "@DotSep"
and produces them separated by a dot and two spaces:
@ID @Code "@MinorNum @DotSep @MinorTitle"
is the same as
@ID @Code "@MinorNum.  @MinorTitle"
However, if either object is empty, the dot and two spaces are
omitted.  It's a fine point, needed mainly for unnumbered chapters
and sections.  @Code "@DotJoin" is the same as @Code "@DotSep" but
dot.join @Index @Code "@DotJoin"
without the two spaces.  @Code "@NoDotSep" is the same as
nodot.sep @Index @Code "@NoDotSep"
@Code "@DotSep" but leaving out the dot, @Code "@NoDotJoin" is the same
nodot.join @Index @Code "@NoDotJoin"
as @Code "@DotJoin" but again leaving out the dot, and @Code "@DashJoin"
dash.join @Index @Code "@DashJoin"
is the same as @Code "@DotJoin" except that `--' replaces the dot.
@PP
Lout uses @Code "@DotSep" between numbers and titles by default.  To
get rid of all dots between numbers and titles it is necessary to
change all occurrences of @Code "@DotSep" in the setup file to
{@Code "@NoDotSep"}.  There are about ten occurrences, depending
on the setup file.
@PP
@Code "@NumSep" {@PageMark numsep} is similar to @Code "@NoDotSep"
except that one space
num.sep @Index @Code "@NumSep"
hungarian @Index { Hungarian and @Code "@NumSep" }
is used, not two, and also the order of the two parts is reversed and
a dot is added if the current language is Hungarian (apparently
Hungarians write `3. Table' where other people write `Table 3').
@Code "@NumSep" is used behind the scenes in a variety of places.
@PP
The present document was produced using @Code "@PageHeaders { Titles }"
with the default values of the sixteen options unchanged, as you might
like to verify.  @Code "@PageHeaders { NoTitles }" is identical to
@Code "@PageHeaders { Titles }" except that {@Code "@MajorNum"},
{@Code "@MajorTitle"}, {@Code "@MinorNum"}, and {@Code "@MinorTitle"}
are always replaced by empty objects.  The description given at the
beginning of this section, `like @Code "Titles" but with the titles
blanked out,' is therefore accurate.
@PP
There is a @Code "@StructPageNums" setup file option that produces
structpagenums. @Index @Code "@StructPageNums"
structured page numbers when it is changed to {@Code Yes}; that is,
page numbers that include a section number, subsection number, and so
on.  Precisely which structure numbers are included is determined by the
@Code "@SectionNumInRunners" option and its relatives.  @Code "@PageHeaders"
must be @Code Titles when structured page numbers are used, and it is
probably best to set @Code "@SectionGap" and some similar options to
{@Code "2b"} (meaning new page) as well.  The @Code "@NumberSeparator"
setup file option (Section {@NumberOf largescale}) affects the format
of the structured page numbers.
@End @Section