@Section
    @Tag { dia_node }
    @Title { Nodes }
@Begin
@PP
@Code "@Diag" has one basic symbol for creating nodes.  It is called
node. @Index { @Code "@Node" }
{@Code "@Node"}, and it takes the following object and encloses it in an
outline whose shape is determined by the {@Code "outline"} option:
@ID {
@Code {
"@Node"
"    outline { curvebox }"
"{ Hello, world }"
}
||7ct
@Diag {
@Node
    outline { curvebox }
{ Hello, world }
}
}
As Section {@NumberOf dia_defi} explains, the @Code outline option may be
used to produce an outline of any shape.  There are also nine values that
produce standard shapes:  {@Code box}, {@Code curvebox}, {@Code shadowbox},
{@Code square}, {@Code diamond}, {@Code polygon}, {@Code isosceles},
{@Code ellipse}, and {@Code circle}.
@PP
The shape of the outline is determined by the @Code outline option, but
its size and position depend on the size and position of its
{@I base}:  the following object with a small margin around it.  For
example, this is how a circle is positioned over its base (shown in
grey):
@ID @OneRow {
@Code {
"@Node"
"    outline { circle }"
"{ Hello, world }"
}
||7ct
@Diag {
@Box paint { lightgrey } outlinestyle { noline } margin { 0c }
@Node
    outline { circle }
{ Hello, world }
}
}
Lout works only with the base, having no idea where the outline is, which
explains why this circle is too high for the space allowed
it.  Section {@NumberOf dia_summ} shows how each of the standard
outlines is positioned over its base.
@PP
The @Code "@Node" symbol has many options, but all of them without
exception share the following very useful property:  they may be given
to the @Code "@Diag" symbol as well, where they apply to every node in
the diagram:
@ID @OneRow {
@Code {
"@Diag"
"    outline { circle }"
"{"
"    @Node @I a"
"    @DP"
"    @Node @I b"
"}"
}
||7ct
@Diag
    outline { circle }
{
    @Node @I a
    @DP
    @Node @I b
}
}
These options also appear in the setup file ({@Code diag});
if set there, they apply to every node in every diagram of the
document.  As the number of nodes increases, it becomes very tedious and
error-prone to duplicate options at all the nodes.  Giving each option
just once, at the @Code "@Diag" symbol or in the setup file, saves time
and makes it easy to change all the nodes into squares or any other shape
later on.  Any setup file option may be overridden in a diagram by giving
the option to its @Code "@Diag" symbol; any @Code "@Diag" option or setup
file option may be overridden at any node by giving the option again there.
@PP
Sometimes a diagram contains several different node types, each with
its own combination of options (for example, the syntax diagrams of
Section {@NumberOf dia_synt} have three node types).  To handle these
cases there are three alternative versions of the @Code "@Node"
symbol, called {@Code "@ANode"}, {@Code "@BNode"}, and
anode.fig @Index { @Code "@ANode" in @Code "@Diag" }
bnode.fig @Index { @Code "@BNode" in @Code "@Diag" }
cnode.fig @Index { @Code "@CNode" in @Code "@Diag" }
{@Code "@CNode"}.  These have exactly the same options as
{@Code "@Node"}, but the @I default values of these options
are different, in that they come from @Code "@Diag" options,
or else setup file options, that have an extra letter in front
of their name:  @Code { a }, @Code { b }, or @Code { c }.  Here is
a small example (see later in this section for the @Code font option):
@ID @OneRow {
@Code @Verbatim {
@Diag
    aoutline { box }
    afont { Italic }
    boutline { curvebox }
    bfont { Bold }
{
    @ANode identifier
    @DP
    @BNode keyword
}
}
||7ct
@Diag
    aoutline { box }
    afont { Italic }
    boutline { curvebox }
    bfont { Bold }
{
    @ANode identifier
    @DP
    @BNode keyword
}
}
Note that when giving an option directly to {@Code "@ANode"},
{@Code "@BNode"}, and {@Code "@CNode"}, the initial @Code { a },
@Code { b }, or @Code { c } used with @Code "@Diag" and in the
setup file is omitted.
@PP
To save time in simple cases, @Code "@Diag" provides nine other
node symbols called
{@Code "@Box"},
box.fig @Index { @Code "@Box" in @Code "@Diag" }
{@Code "@CurveBox"},
curvebox.fig @Index { @Code "@CurveBox" in @Code "@Diag" }
{@Code "@ShadowBox"},
shadowbox.fig @Index { @Code "@ShadowBox" in @Code "@Diag" }
{@Code "@Square"},
square. @Index @Code "@Square"
{@Code "@Diamond"},
diamond. @Index @Code "@Diamond"
{@Code "@Polygon"},
{@Code "@Isosceles"},
isosceles. @Index @Code "@Isosceles"
{@Code "@Ellipse"},
ellipse. @Index @Code "@Ellipse"
and {@Code "@Circle"}.  These are just abbreviations for @Code "@Node"
with the appropriate value of {@Code outline}, nothing more.  They take
the same options as {@Code "@Node"} (except that @Code outline is
already fixed), and everything works in the same way.
@PP
There is a @Code shadow option which determines the depth of the shadow
in shadow boxes:
@ID {
@Code {
"@Node"
"    outline { shadowbox }"
"    shadow { 0.4f }"
"{ WARNING }"
}
||7ct
@Diag {
@Node
    outline { shadowbox }
    shadow { 0.4f }
{ WARNING }
}
}
This example shows the default value, 0.4 times the current font
size.  For polygons there is a @Code sides option for specifying the number
polygon. @Index @Code "@Polygon"
of sides, and an @Code angle option for rotating the outline:
@IL
@LI {
@Code {
"@Polygon"
"   sides { 5 }"
}
||7ct
@Diag {
@Polygon
   sides { 5 }
{ 1c @High 1c @Wide }
}
}

@LI {
@Code {
"@Polygon"
"   sides { 5 }"
"   angle { 0d }"
}
||7ct
@Diag {
@Polygon
   sides { 5 }
   angle { 0d }
{ 1c @High 1c @Wide }
}
}
@EL
Setting @Code angle to @Code 0d causes the first vertex to be placed
directly underneath the centre, and as the angle increases, the
position of the first vertex rotates anticlockwise.  The defaults are
3 sides and the angle that gives the polygon a
horizontal base (i.e. 180 degrees divided by the number of sides).  Thus
the two cases with symmetry about a vertical axis are obtained by the
default angle and @Code "0d" respectively, which is convenient.  The
{@Code "shadow"}, {@Code "sides"}, and {@Code "angle"} options may be
given to any node, and also to {@Code "@Diag"} and in the setup file,
where they apply to every node as usual.  However, they only affect the
appearance of shadow boxes and polygons, respectively.
@PP
The {@Code outlinestyle}, {@Code outlinedashlength}, and {@Code outlinewidth}
options apply to any node and affect the appearance of the outline:
@ID @OneRow {
@Code {
"@CurveBox"
"   outlinestyle { solid }"
"   outlinedashlength { 0.2f }"
"   outlinewidth { thin }"
"{ Hello, world }"
}
||7ct
@Diag {
@CurveBox
   outlinestyle { solid }
   outlinedashlength { 0.2f }
   outlinewidth { thin }
{ Hello, world }
}
}
This example shows the default values of these options.  The
{@Code outlinestyle} option may be {@Code solid}, {@Code dashed},
dashed. @Index { dashed lines }
dotted. @Index { dotted lines }
{@Code cdashed}, {@Code dotted}, or {@Code noline}:
@ID @OneRow {
@Code {
"@CurveBox"
"   outlinestyle { cdashed }"
"{ Hello, world }"
}
||7ct
@Diag {
@CurveBox
   outlinestyle { cdashed }
{ Hello, world }
}
}
The @Code dashed option makes all dashes the same length, whereas
@Code cdashed halves the length of the first and last dash on each segment,
which usually looks better.  The length of dashes is {@Code outlinedashlength},
and the distance between dashes or dots is at most {@Code outlinedashlength},
reduced to make the dashes or dots fit evenly.  The @Code outlinewidth
option determines the width of the line, dashes, or dots, and may be
{@Code thin}, {@Code medium}, {@Code thick}, or any length.  The values
used for {@Code thin}, {@Code medium}, and {@Code thick} are
{@Code 0.04f}, {@Code 0.08f}, and {@Code 0.12f}.
@PP
The {@Code outlinestyle} option may contain a sequence of the values
mentioned above, meaning that they are to be applied in turn to each
segment of the outline:
@ID @OneRow {
@Code {
"@CurveBox"
"   outlinestyle { solid cdashed }"
"{ Hello, world }"
}
||7ct
@Diag {
@CurveBox
   outlinestyle { solid cdashed }
{ Hello, world }
}
}
If there are more segments than values, {@Code outlinestyle} cycles back
to the first value again; this is why a single value is applied to all
segments.  Section {@NumberOf dia_summ} shows how each of the
standard shapes is divided into segments.
@PP
Nodes may be painted any of the colours listed in Section
{@NumberOf colour}, using the @Code "paint" option:
@ID @OneRow {
@Code {
"@Box"
"   paint { grey }"
"@Diamond"
"   outlinestyle { noline }"
"   paint { white }"
"{ Hello, world }"
}
||7ct
@Diag {
@Box
   paint { grey }
@Diamond
   outlinestyle { noline }
   paint { white }
{ Hello, world }
}
}
In this example the object following @Code "@Box" is a diamond containing
{@Code "Hello, world"}.  The default value of @Code "paint" is
{@Code nopaint}, a special value (not a colour) meaning don't use any paint.
@PP
When painting it is important to know what order things are done in, because
anything put down earlier will disappear under the paint.  This is why
@Code nopaint and @Code white are different.  Painting is done first, then
boundaries, and finally the following object.
@PP
Each node symbol has 
@Code "font" and @Code "break" options which may be used to
set the font and paragraph breaking style of the following object:
@ID @OneRow {
@Code {
"@Box"
"    font { Helvetica Base }"
"    break { clines }"
"{"
"WARNING"
"DANGEROUS"
"PENGUINS"
"}"
}
||7ct
@Diag {
@Box
    font { Helvetica Base }
    break { clines }
{
WARNING
DANGEROUS
PENGUINS
}
}
}
Both options have empty default values, which leave the font and break
style unchanged.  There is also a @Code "format" option for making more
radical changes to the appearance of the following object:
@ID @OneRow {
@Code {
"@Box"
"    format {"
"        {0.8 1.5} @Scale @S @Body"
"    }"
"{"
"Dangerous Penguins"
"}"
}
||7ct
@Diag {
@Box
    format { { 0.8 1.5 } @Scale @S @Body }
{
Dangerous Penguins
}
}
}
The result is the @Code "format" option with any @Code "@Body" symbol
within it replaced by the following object.  These are very useful when
attached to the @Code "@Diag" symbol:
@ID @OneRow @Code {
"@Diag"
"    font { Helvetica Base }"
"    break { clines }"
"    format { { 0.8 1.5 } @Scale @S @Body }"
"{"
"    ..."
"}"
}
since then they apply to every node, as usual, thereby eliminating
a lot of tedious, error-prone duplication of formatting information
at each node.
@PP
The @Code margin option determines the size of the margin added to
the following object:
@ID @OneRow {
@Code {
"@Box"
"    margin { 0c }"
"{ Hello, world }"
}
||7ct
@Diag {
@Box
    margin { 0c }
{ Hello, world }
}
}
These margins are included in the node's base (described above), so a
larger margin enlarges the base and hence the outline as well.  The
default value of @Code margin is {@Code 0.6f} (six-tenths of the current
font size), and so the margin will automatically increase when the font size
does, for example in overhead transparencies.
@PP
The @Code margin option adds the same margin to all four sides.  For
finer control, the @Code hmargin option determines the horizontal (left
and right) margins only, overriding {@Code margin}.  Similarly, the
@Code vmargin option determines the vertical (top and foot) margins.  There
are also {@Code leftmargin}, {@Code rightmargin},
{@Code topmargin}, and {@Code footmargin} options which override
{@Code margin}, {@Code hmargin}, and {@Code vmargin}.
@PP
When nodes appear side by side, the {@Code valign} option is
useful for controlling their vertical position with respect to each
other.  For example,
@ID @OneRow {
@Code {
"@Diag"
"    valign { foot }"
"{"
"@Box font { 24p } Big"
"@Box font { 8p } Small"
"}"
}
||7ct
@Diag
    valign { foot }
{
@Box font { 24p } Big
@Box font { 8p } Small
}
}
causes the feet of the boxes to be aligned.  In this example it is
applied to all nodes at once, but of course it can be applied
to individual nodes as well.  The value of {@Code valign} can be a
length, which means that the point of alignment is
to be that far down from the top of the base (including margins); or
it may be {@Code top}, {@Code ctr}, or {@Code foot}, meaning alignment
through the top, centre (the default value), or foot.
@PP
The {@Code vsize} option specifies a particular
height for a node (not including margins):
@ID @OneRow {
@Code {
"@Diag"
"    vsize { 2f }"
"{"
"@Box font { 24p } Big"
"@Box font { 8p } Small"
"}"
}
||7ct
@Diag
    vsize { 2f }
{
@Box font { 24p } Big
@Box font { 8p } Small
}
}
The font size used when calculating @Code vsize is not affected by
the value of any @Code font option.  If the following object is too
tall for the chosen height, Lout will print a warning message (`forced
to enlarge {@Code "@High"}', probably) and enlarge the base.
@PP
There is a @Code vindent option which is effective only when @Code vsize
is used.  It controls where in the vertical space the following object
is to appear:
@ID @OneRow {
@Code {
"@Diag"
"    vsize { 3f }"
"{"
"@Box vindent { top } Top"
"@Box Centre"
"@Box vindent { foot } Foot"
"}"
}
||7ct
@Diag
    vsize { 3f }
    vindent { ctr }
{
@Box vindent { top } Top
@Box Centre
@Box vindent { foot } Foot
}
}
The value may be {@Code top} for at the top, {@Code ctr} (the default
value) for in the centre, {@Code foot} for at the foot, or a length,
meaning that distance down from the top.  These values are the same as
for the @Code valign option.
@PP
Small discrepancies in the size of nodes can be very annoying,
particularly when the nodes appear side by side:
@ID @OneRow {
@Code {
"@Diag"
"{"
"@Box Hole @Box in"
"@Box my @Box pocket"
"}"
}
||7ct
@Diag
{
@Box Hole @Box in
@Box my @Box pocket
}
}
These are caused by the slightly different heights of the objects within
the nodes.  Selecting a fixed vertical size for all nodes goes some way
towards solving this problem:
@ID @OneRow {
@Code {
"@Diag"
"    vsize { 1f }"
"{"
"@Box Hole @Box in"
"@Box my @Box pocket"
"}"
}
||7ct
@Diag
    vsize { 1f }
{
@Box Hole @Box in
@Box my @Box pocket
}
}
The size @Code "1f" is a good choice because most fonts are designed to
be @Code "1f" high from the top of the tallest character to the foot of the
deepest.  However, there is still a problem with the baselines of the words
being misaligned.  A better solution is to insert a @I { vertical strut }
into each node:  an invisible object with zero width and height equal to
{@Code 1f}.  This is done using the @Code vstrut option:
@ID @OneRow {
@Code {
"@Diag"
"    vstrut { yes }"
"{"
"@Box Hole @Box in"
"@Box my @Box pocket"
"}"
}
||7ct
@Diag
    vstrut { yes }
{
@Box Hole @Box in
@Box my @Box pocket
}
}
The @Code vstrut option may be {@Code yes}, {@Code no} (the default value), or
a length, meaning to insert a strut of this height.  So @Code "vstrut { yes }"
is equivalent to {@Code "vstrut { 1.0f }"}.
@PP
There are {@Code halign}, {@Code hsize}, {@Code hindent}, and {@Code hstrut}
options which work horizontally exactly as {@Code valign}, {@Code vsize},
{@Code vindent}, and {@Code vstrut} work vertically, except that they
use {@Code left} and {@Code right} where the vertical ones use
{@Code top} and {@Code foot}.  The best way to fix horizontal size
discrepancies is with {@Code hsize}, not {@Code hstrut}.
@End @Section