rtsi.com/2014.01.www.rtsi.com.tar/www.rtsi.com/OS9/OSK/APPS/lout2.lzh/LOUT2/DOC/TR.LOUT/ch2.05

Text File | 1994-01-25 | 5KB | 132 lines

@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 { What gap to replace a single space between two objects by (also
defining the @Code s unit); }
@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. }
@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, @@Space, and @@Break symbols.
@PP
There are no standard default values for style.  Instead one must ensure
that the root galley or each of its components is enclosed in @@Font
and @@Break symbols.  From there the style is passed to incoming galleys
and the objects within them.
@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 @Code {
"def @Box 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}).  The result of
@ID @Code {
"5c @Wide @Box metempsychosis"
}
is
@ID {
5c @Wide @Box metempsychosis
}
The widest that @Code "@Box 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 @Code {
"5c @Wide @HContract @Box metempsychosis"
}
produces
@ID {
5c @Wide @HContract @Box metempsychosis
}
The object @Code "@HContract @Box metempsychosis" is still five centimetres
wide, but the object @Code "@Box metempsychosis" has been reduced.
@PP
The second of the three exceptions is the horizontal concatenation symbol
@Code "|" (and also {@Code "&"}).  Consider this example:
@ID @Code {
"5c @Wide @Box { 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 @Box { 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 @Code {
"5c @Wide { @Box A  |1c  @Box B  |1c  @Box C }"
}
has result
@ID {
5c @Wide { @Box A  |1c  @Box B  |1c  @Box 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 { @Box 953^.05 /0.5c @Box 2^.8286 }"
}
has result
@ID {
@HContract { @Box 953^.05 /0.5c @Box 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