@Section
   @Title { The style and size of objects }
   @Tag { size }
@Begin
@PP
This section explains how Lout determines the style and size of each
object.  Together, these attributes determine the object's final
appearance in the output.
style @Index { Style of an object }
@PP
The style of an object comprises the following:
@BulletList
@ListItem { Which font family, face and size to use (also defining the
@Code f unit); }
@ListItem { Whether small capitals are in effect or not; }
@ListItem { What gap to replace a single space between two objects by (also
defining the @Code s unit); }
@ListItem { The interpretation to place on white space separating
two objects ({@Code lout}, {@Code compress}, {@Code separate}, {@Code troff},
or {@Code tex} as in Section {@NumberOf space}); }
@ListItem { The current value of the @Code y and @Code z units of
measurement (Section {@NumberOf yunit}); }
@ListItem { The kind of paragraph breaking to employ ({@Code adjust},
{@Code ragged}, etc.) }
@ListItem { What gap to insert between the lines of paragraphs
(also defining the @Code v unit); }
@ListItem { Whether to permit hyphenation or not; }
@ListItem { What colour the object is to appear in; }
@ListItem { Whether @@Outline is in effect; }
@ListItem { The language of the object; }
@ListItem { Whether @@VAdjust, @@HAdjust and @@PAdjust are in effect. }
@EndList
The style of an object depends on where it appears in the final
document.  For example, the style of a parameter depends on where it is
used; the style of a galley is the style of the first target that it
attempts to attach itself to.  Of course, the style of any object can be
changed by using the @@Font, @@Break, @@Space, @@SetColour or
@@SetColor, @@Outline, and @@Language symbols.
@PP
There are no standard default values for style, except that small capitals
and outlining are initially off, the interpretation of white space is
initially {@Code lout}, and the values of the @Code y and @Code z units
are zero.  Therefore one must ensure that the root galley or each of its
components is enclosed in @@Font, @@Break, @@SetColour or @@SetColor, and
@@Language symbols.  From there the style is passed to incoming galleys
and the objects within them.  Enclosure in @@Space is not required because
the @Code "s" unit is also set by @@Font (Section {@NumberOf space}).
@PP
width. @Index { Width of an object }
height. @Index { Height of an object }
size. @Index { Size of an object }
The remainder of this section explains how the size of each object (its
width and height on the printed page) is determined.  We will treat width
only, since height is determined in exactly the same way, except that the
complications introduced by paragraph breaking are absent.
@PP
With three exceptions (see below), the width of an object is as large as
it possibly could be without violating a @@Wide symbol or intruding into
the space occupied by neighbouring gaps or objects.  As an aid to
investigating this rule, we will use the definition
@ID @OneRow @Code {
"def @TightBox right x"
"{"
"  \"0 0 moveto xsize 0 lineto xsize ysize lineto 0 ysize lineto closepath stroke\""
"  @Graphic x"
"}"
}
which draws a box around the boundary of its right parameter (Section
{@NumberOf graphic}) with no margin.  The result of
@ID @Code {
"5c @Wide @TightBox metempsychosis"
}
is
@ID {
5c @Wide @TightBox metempsychosis
}
The widest that @Code "@TightBox metempsychosis" could possibly be is five
centimetres, and accordingly that is its width.  The same applies to
{@Code metempsychosis}, which is five centimetres wide as well.  Note
carefully that there is no object in this example whose width is equal
to the sum of the widths of the letters of {@Code metempsychosis}.
@PP
The first of the three exceptions to the `as wide as possible' rule is the
@@HContract symbol, which causes the width of its right parameter to be
reduced to a reasonable minimum (a formal definition will not be attempted):
@ID @OneRow @Code {
"5c @Wide @HContract @TightBox metempsychosis"
}
produces
@ID {
5c @Wide @HContract @TightBox metempsychosis
}
The object @Code "@HContract @TightBox metempsychosis" is still five centimetres
wide, but the object @Code "@TightBox metempsychosis" has been reduced.
@PP
The second of the three exceptions is the horizontal concatenation symbol
@Code "|" (and also {@Code "&"}).  Consider this example:
@ID @OneRow @Code {
"5c @Wide @TightBox { A  |1c  B  |1c  C }"
}
As usual, the right parameter of @@Wide is five centimetres wide, and
the result looks like this:
@ID {
5c @Wide @TightBox { A  |1c  B  |1c  C }
}
Lout has to apportion the size minus inter-column gaps among the three
columns.
@PP
If the columns are wide enough to require paragraph breaking, Lout will
assign sizes to the columns in such a way as to leave narrow columns
unbroken and break wider columns to equal width, occupying the full
size.  Otherwise, paragraph breaking is not required, and each column
will be assigned a reasonable minimum size in the manner of @@HContract,
except that the last column receives all the leftover width.  For example,
@ID @OneRow @Code {
"5c @Wide { @TightBox A  |1c  @TightBox B  |1c  @TightBox C }"
}
has result
@ID {
5c @Wide { @TightBox A  |1c  @TightBox B  |1c  @TightBox C }
}
If it is desired that the leftover width remain unused, rather than
going into the last column, an empty column can be appended, or the last
column can be enclosed in @@HContract.  Two other ways to apportion the
leftover width are provided by the @@HExpand and @@HAdjust symbols
(Sections {@NumberOf hexpand} and {@NumberOf hadjust}).
@PP
The third and final exception to the `as wide as possible' rule concerns
the components of the root galley.  Each is considered to be enclosed
root.galley.size @SubIndex { size of components of }
in @@HContract and @@VContract symbols.
@PP
Up to this point we have treated width as a single quantity, but of
course it has two parts:  width to left and right of the mark.  The
`as wide as possible' rule applies to both directions:
@ID @Code {
"@HContract { @TightBox 953^.05 /0.5c @TightBox 2^.8286 }"
}
has result
@ID {
@HContract { @TightBox 953^.05 /0.5c @TightBox 2^.8286 }
}
Leftover width usually goes to the right, as we have seen, but here some
width was available only to the left of {@Code "2.8286"} owing to the
column mark alignment.
@End @Section