# List of attribute types
# Each item consists of line of the form :<typename>
# followed by a description of the type in HTML
# The items are alphabetized when the page is created.
#
# The type <typename> is given the anchor k:<typename>, so
# the description can be linked with <HREF="k:<typename>">
:addDouble
<P>A double with an optional prefix '+'.
:addPoint
<P>A <A HREF="#k:point">point</A> with an optional prefix '+'.
#:aspectType
#<p>An aspect ratio, double, followed optionally by a ',' and a maximum pass 
#count. If the aspect ratio is given, but no maximum pass count, the
#latter defaults to 5.
:arrowType
<TABLE>
  <TR><TD>"normal"<TD><IMG SRC="a_normal.gif">
      <TD>"inv"<TD><IMG SRC="a_inv.gif"></TR>
  <TR><TD>"dot"<TD><IMG SRC="a_dot.gif">
      <TD>"invdot"<TD><IMG SRC="a_invdot.gif"></TR>
  <TR><TD>"odot"<TD><IMG SRC="a_odot.gif">
      <TD>"invodot"<TD><IMG SRC="a_invodot.gif"></TR>
  <TR><TD>"none"<TD><IMG SRC="a_none.gif">
      <TD>"tee"<TD><IMG SRC="a_tee.gif"></TR>
  <TR><TD>"empty"<TD><IMG SRC="a_empty.gif">
      <TD>"invempty"<TD><IMG SRC="a_invempty.gif"></TR>
  <TR><TD>"diamond"<TD><IMG SRC="a_diamond.gif">
      <TD>"odiamond"<TD><IMG SRC="a_odiamond.gif"></TR>
  <TR><TD>"ediamond"<TD><IMG SRC="a_ediamond.gif">
      <TD>"crow"<TD><IMG SRC="a_crow.gif"></TR>
  <TR><TD>"box"<TD><IMG SRC="a_box.gif">
      <TD>"obox"<TD><IMG SRC="a_obox.gif"></TR>
  <TR><TD>"open"<TD><IMG SRC="a_open.gif">
      <TD>"halfopen"<TD><IMG SRC="a_halfopen.gif"></TR>
  <TR><TD>"vee"<TD><IMG SRC="a_open.gif">
</TABLE>
<P>
The examples above show a set of commonly used arrow shapes.
There is a grammar of <A HREF=arrows.html>arrow shapes</A>
which can be used to describe a collection of 3,111,696 arrow combinations of the 
42 variations of the primitive set of 11 arrows. The basic arrows shown
above contain most of the primitive shapes
(<TT>box</TT>, <TT>crow</TT>, <TT>diamond</TT>,
<TT>dot</TT>, <TT>inv</TT>, <TT>none</tt>,
<TT>normal</tt>, <TT>tee</TT>, <TT>vee</TT>)
plus ones that can be derived from the grammar
(<TT>odot</TT>, <TT>invdot</TT>, <TT>invodot</TT>,
<TT>obox</TT>, <TT>odiamond</TT>)
plus some supported as special cases for backward-compatibility
(<TT>ediamond</TT>, <TT>open</TT>, <TT>halfopen</TT>,
<TT>empty</TT>, <TT>invempty</TT>).
:clusterMode
"local","global","none"
:color
Colors can be specified using one of four formats.
       <TABLE><TR><TD>"#%2x%2x%2x"<TD>Red-Green-Blue (RGB)</TR>
       <TR><TD>"#%2x%2x%2x%2x"<TD>Red-Green-Blue-Alpha (RGBA)</TR>
       <TR><TD>"H[,&#160;]+S[,&#160;]+V"<TD>Hue-Saturation-Value (HSV) 0.0 <= H,S,V <= 1.0</TR>
       <TR><TD>string<TD><A HREF=colors.html>color name</A></TR></TABLE>
 The specification for the RGB and RGBA formats are the format strings used by
 <TT>sscanf</TT> to scan the color value. Thus, these values have the form
 "#RGB" or "#RGBA", where R, G, B, and A each consist of 2 hexadecimal
 digits, and can be separated by whitespace. HSV colors have the form of 3
 numbers between 0 and 1, separated by whitespace or commas.
<P>
String-valued color specifications are case-insensitive and interpreted
in the context of the current color scheme, as specified by the
<A HREF=#d:colorscheme>colorscheme</A> attribute. If this is undefined,
the X11 naming scheme will be used.
An initial <TT>"/"</TT> character can be used to override the use of
the <TT>colorscheme</TT> attribute. In particular, a single initial
<TT>"/"</TT> will cause the string to be evaluated using the default
X11 naming. If the color value has the form <TT>"/ssss/yyyy"</TT>,
the name <TT>yyyy</TT> is interpreted using the schema <TT>ssss</TT>.
If the color scheme name is empty, i.e., the color has the
form <TT>"//yyyy"</TT>, the <TT>colorscheme</TT> attribute is used.
Thus, the forms <TT>"yyyy"</TT> and <TT>"//yyyy"</TT> are
equivalent.
<P>At present, Graphviz recognizes the default color scheme <TT>X11</TT>,
and the <A HREF="colors.html#brewer">Brewer color schemes</A> (cf. <A HREF="http://www.personal.psu.edu/faculty/c/a/cab38/ColorBrewer/ColorBrewer_intro.html">ColorBrewer</A>). Please note that Brewer
color schemes are covered by this <A HREF=colors.html#brewer_license>license</A>.
<P>
Examples:<BR>
  <TABLE border=1>
    <TR><TH>Color<TH>RGB<TH>HSV<TH>String</TR>
    <TR><TD align=center bgcolor=#ffffff>White<TD>"#ffffff"<TD>"0.000 0.000 1.000"<TD>"white"</TR>
    <TR><TD align=center bgcolor=#000000><font color=white>Black</font><TD>"#000000"<TD>"0.000 0.000 0.000"<TD>"black"</TR>
    <TR><TD align=center bgcolor=#ff0000>Red<TD>"#ff0000"<TD>"0.000 1.000 1.000"<TD>"red"</TR>
    <TR><TD align=center bgcolor=#40e0d0>Turquoise<TD>"#40e0d0"<TD>"0.482 0.714 0.878"<TD>"turquoise"</TR>
    <TR><TD align=center bgcolor=#a0522d>Sienna<TD>"#a0522d"<TD>"0.051 0.718 0.627"<TD>"sienna"</TR>
  </TABLE>
<P>
 The string value <TT>transparent</TT> can be used to indicate no color.
 This is only available in the output formats
 ps, svg, fig, vmrl, and the bitmap formats. It can be used whenever a
 color is needed but is most useful with
 the <A HREF=#d:bgcolor>bgcolor</A> attribute.
 Usually, the same effect can be achieved by setting
 <A HREF=#d:style>style</A> to <TT>invis</TT>.
:colorList
A colon-separated list of weighted color values: <I>WC</I>(:<I>WC</I>)*
where each <I>WC</I> has the form <I>C(;F)?</I> with C a <A HREF=#k:color>color</A> value
and the optional <I>F</I> a floating-point number, 0 &le; <I>F</I> &le; 1. The sum of the 
floating-point numbers in a <TT>colorList</TT> must sum to at most 1.
<P>
<b>NOTE:</b> Gradient fills, described below, are currently only available via CAIRO or SVG rendering.
<P>
If the colorList value specifies multiple colors, with no weights, and a filled style is specified,
a linear gradient fill is done using the first two colors.
If weights are present, a degenerate linear gradient fill is done. This essentially does a fill using
two colors, with the weights specifying how much of region is filled with each color. 
If the <A HREF=#a:style>style</A> attribute contains the value <tt>radial</tt>, then
a radial gradient fill is done. These fills work with any shape. 
<P>
For certain shapes, the <A HREF=#a:style>style</A> attribute can be set
to do fills using more than 2 colors. See the <A HREF=#k:style>style</A> type for more information.
<P>
The following table shows some variations of the <TT>yellow:blue</TT> color list depending on the
<A HREF=#a:style>style</A> and <A HREF=#a:gradientangle>gradientangle</A> attributes.
  <TABLE border=1>
    <TR><TH>Gradient angle<TH><tt>style=filled</tt><TH><tt>style=filled<br>fillcolor=yellow;0.3:blue</tt><TH><tt>style=radial</tt></TR>
    <TR><TD align=center>0<TD><IMG SRC="g_lin0.png"><TD ALIGN="CENTER"><IMG SRC="g_wlin0.png"><TD><IMG SRC="g_rad0.png"></TR>
    <TR><TD align=center>45<TD><IMG SRC="g_lin45.png"><TD ALIGN="CENTER"><IMG SRC="g_wlin45.png"><TD><IMG SRC="g_rad45.png"></TR>
    <TR><TD align=center>90<TD><IMG SRC="g_lin90.png"><TD ALIGN="CENTER"><IMG SRC="g_wlin90.png"><TD><IMG SRC="g_rad90.png"></TR>
    <TR><TD align=center>180<TD><IMG SRC="g_lin180.png"><TD ALIGN="CENTER"><IMG SRC="g_wlin180.png"><TD><IMG SRC="g_rad180.png"></TR>
    <TR><TD align=center>270<TD><IMG SRC="g_lin270.png"><TD ALIGN="CENTER"><IMG SRC="g_wlin270.png"><TD><IMG SRC="g_rad270.png"></TR>
    <TR><TD align=center>360<TD><IMG SRC="g_lin360.png"><TD ALIGN="CENTER"><IMG SRC="g_wlin360.png"><TD><IMG SRC="g_rad360.png"></TR>
  </TABLE>
:dirType
For an edge <CODE>T -> H;</CODE>
  <TABLE>
  <TR><TD>"forward"<TD><IMG SRC="forward.gif">
      <TD>"back"<TD><IMG SRC="back.gif"></TR>
  <TR><TD>"both"<TD><IMG SRC="both.gif">
      <TD>"none"<TD><IMG SRC="nohead.gif"></TR>
  </TABLE>
That is, a glyph is drawn at the head end of an edge if and only
if dirType is "forward" or "both";
a glyph is drawn at the tail end of an edge if and only
if dirType is "back" or "both";
<P>
For undirected edges <CODE>T -- H;</CODE>, one of the nodes, usually
the righthand one, is treated as the head for the purpose of
interpreting "forward" and "back".
:doubleList
A colon-separated list of doubles: "<I>%f</I>(:<I>%f</I>)*"
 where each <I>%f</I> is a double.
:escString
A string allowing escape sequences which are replaced according
to the context.
For node attributes, the substring "&#92;N" is replaced by the name of the node,
and the substring "&#92;G" by the name of the graph.
For graph or cluster attributes, the substring "&#92;G" is replaced by the
name of the graph or cluster.
For edge attributes, the substring "&#92;E" is replaced by the name of the edge,
the substring "&#92;G" is replaced by the name of the graph or cluster,
and the substrings "&#92;T" and "&#92;H" by the names of
the tail and head nodes, respectively.
The name of an edge is the string formed from the name of the
tail node, the appropriate edge operator ("--" or "->") and the name of the
head node.
In all cases, the substring "&#92;L" is replaced by the object's label attribute.
<P>
In addition, if the associated attribute is
<A HREF=#a:label>label</A>,
<A HREF=#a:headlabel>headlabel</A> or <A HREF=#a:taillabel>taillabel</A>,
the escape sequences "&#92;n", "&#92;l" and "&#92;r"
divide the label into lines, centered, left-justified, and right-justified,
respectively.
<P>
Obviously, one can use "&#92;&#92;" to get a single backslash. A backslash appearing before any
character not listed above is ignored.
:lblString
an <A HREF=#k:escString>escString</A>
or an <A HREF=shapes.html#html>HTML label</A>.
:layerList
list of strings separated by characters from the
<A HREF=#a:layersep>layersep</A> attribute (by default, colons,
tabs or spaces), defining <A HREF=#a:layer>layer</A>
names and implicitly numbered 1,2,...
:layerRange
specifies a list of layers defined by the <A HREF=#a:layers>layers</A> attribute.
It consists of a list of layer intervals separated by any collection of characters from
the <A HREF=#a:layerlistsep>layerlistsep</A> attribute.
Each layer interval is specified as either a
layerId or a layerId<B>s</B>layerId<BR>, where layerId = "all",
a decimal integer or a <A HREF=#a:layer>layer</A> name.
(An integer i corresponds to layer i, layers being numbered from 1.)
The string <B>s</B> consists of 1 or more separator characters specified
by the <A HREF=#a:layersep>layersep</A> attribute.
<P>
Thus, assuming the default values for <A HREF=#a:layersep>layersep</A>
and <A HREF=#a:layerlistsep>layerlistsep</A>, if <TT>layers="a:b:c:d:e:f:g:h"</TT>, the
layerRange string <TT>layers="a:b,d,f:all"</TT> would denote the layers
<TT>a b d f g h"</TT>.
:outputMode
"breadthfirst","nodesfirst","edgesfirst"
These specify the order in which nodes and edges are drawn in concrete
output. The default "breadthfirst" is the simplest, but when the graph
layout does not avoid edge-node overlap, this mode will sometimes have
edges drawn over nodes and sometimes on top of nodes. If the mode
"nodesfirst" is chosen, all nodes are drawn first, followed by the
edges. This guarantees an edge-node overlap will not be mistaken for
an edge ending at a node. On the other hand, usually for aesthetic
reasons, it may be desirable that all edges appear beneath nodes, even
if the resulting drawing is ambiguous. This can be achieved by choosing
"edgesfirst".
:packMode
"node", "clust" , "graph" , "array(_<I>flags</I>)?(%d)?"
<P>
The modes "node", "clust" or "graph"
specify that the components should be packed together tightly, using
the specified granularity.
A value of "node" causes
packing at the node and edge level, with no overlapping of these objects.
This produces a layout with the least area, but it also allows interleaving,
where a node of one component may lie between two nodes in another
component. A value of "graph" does a packing using the bounding box of the
component. Thus, there will be a rectangular region around a component
free of elements of any other component.
A value of "clust" guarantees that top-level clusters are kept intact.
What effect a value has also depends on the layout algorithm. For
example, neato does not support clusters, so a value of "clust" will
have the same effect as the default "node" value.
<P>
The mode "array(_<I>flag</I>)?(%d)?"
indicates that the components should be packed at the 
graph level into an array of graphs. By default, the components
are in row-major order, with the number of columns roughly the
square root of the number of components. If the optional flags
contains 'c', then column-major order is used. Finally, if the
optional integer suffix is used, this specifies the number of 
columns for row-major or the number of rows for column-major.
Thus, the mode "array_c4" indicates array packing, with 4 rows,
starting in the upper left and going down the first column, then
down the second column, etc., until all components are used.
<P>
If a graph is smaller than the array cell it occupies, it is centered by default.
The optional flags may contain 't', 'b', 'l', or 'r', indicating that the graphs
should be aligned along the top, bottom, left or right, respectively.
<P>
If the optional flags contains 'u', this causes the insertion
order of elements in the array to be determined by user-supplied
values. Each component can specify its sort value by a 
non-negative integer using the <A HREF="#d:sortv">sortv</A> attribute. 
Components are
inserted in order, starting with the one with the smallest
sort value. If no sort value is specified, zero is used.
:pagedir
"BL", "BR", "TL", "TR", "RB", "RT", "LB", "LT".
These specify the 8 row or column major orders for traversing a
rectangular array, the first character corresponding to the major
order and the second to the minor order. Thus, for "BL", the
major order is from bottom to top, and the minor order is from left
to right. This means the bottom row is traversed first, from left
to right, then the next row up, from left to right, and so on,
until the topmost row is traversed.
:point
"%f,%f('!')?" representing the point (x,y). The
optional '!' indicates the
node position should not change (input-only).
<P>
If <A HREF=#d:dim>dim</A> is 3, <B>point</B> may also have
the format "%f,%f,%f('!')?" to represent the point (x,y,z).
:pointList
A list of points, separated by spaces.
:portPos
modifier indicating where on a node an edge should be aimed.
It has the form <TT><I>portname</I>(:<I>compass_point</I>)?</TT>
or <TT><I>compass_point</I></TT>.
If the first form is used, the corresponding node must either have
<A HREF=shapes.html#record>record</A> shape with one of its fields
having the given <I>portname</I>,
or have an <A HREF=shapes.html#html>HTML-like label</A>, one of
whose components has a <TT>PORT</TT> attribute set to <I>portname</I>.
<P>
If a compass point is used, it must have the form
<TT>"n","ne","e","se","s","sw","w","nw","c","_"</TT>. This modifies the edge
placement to aim for the corresponding compass point on the port or,
in the second form where no <I>portname</I> is supplied, on the node
itself. The compass point "c" specifies the center of the node or port.
The compass point "_" specifies that an appropriate side of the port
adjacent to the exterior of the node should be used, if such exists.
Otherwise, the center is used.
If no compass point is used with a portname, the default value is "_".
<P>
<P>
This attribute can be attached to an edge using the
<A HREF=#d:headport>headport</A> and
<A HREF=#d:tailport>tailport</A> attributes, or as part of the
edge description as in
<CENTER>
<TT>node1:port1 -> node2:port5:nw;</TT>
</CENTER>
<P>
Note that it is legal to have a portname the same as one of
the compass points. In this case, this reference will be resolved to
the port. Thus, if node <TT>A</TT> has a port <TT>w</TT>, then
<TT>headport=w</TT> will refer to the port and not the compass point.
At present, in this case, there is no way to specify that the compass
point should be used.
:quadType
"normal", "fast", "none". 
<P>
Using "fast" gives about a 2-4 times overall speedup compared with "normal", 
though layout quality can suffer a little. 
:rankdir
"TB", "LR", "BT", "RL", corresponding to directed graphs drawn
from top to bottom, from left to right, from bottom to top, and from
right to left, respectively.
:splineType
spline ( ';' spline )*<BR>
<TABLE>
 <TR><TD ALIGN=right>where spline<TD>=<TD>(endp)? (startp)? point (triple)+</TR>
 <TR><TD ALIGN=right>and triple<TD>=<TD>point point point</TR>
 <TR><TD ALIGN=right>and endp<TD>=<TD>"e,%f,%f"</TR>
 <TR><TD ALIGN=right>and startp<TD>=<TD>"s,%f,%f"</TR>
</TABLE>
If a spline has points p<SUB>1</SUB> p<SUB>2</SUB> p<SUB>3</SUB> ... p<SUB>n</SUB>, (n = 1 (mod 3)), the points
 correspond to the control points of a cubic B-spline from p<SUB>1</SUB> to p<SUB>n</SUB>. If startp
 is given, it touches one node of the edge, and the arrowhead
 goes from p<SUB>1</SUB> to startp. If startp is not given, p<SUB>1</SUB> touches a node.
 Similarly for p<SUB>n</SUB>  and endp.
:rankType
"same", "min", "source", "max", "sink"
:rect
"%f,%f,%f,%f"  The rectangle llx,lly,urx,ury gives the coordinates, in
 points, of the lower-left corner (llx,lly) and the upper-right corner
 (urx,ury).
:smoothType
Values are "none", "avg_dist", "graph_dist", "power_dist", "rng", 
"spring" and "triangle".
:style
styleItem ( ',' styleItem )*<BR>
<TABLE>
<TR><TD ALIGN=right>where styleItem<TD>=<TD>name or name'('args')'</TR>
<TR><TD ALIGN=right>and args<TD>=<TD>name ( ',' name )*</TR>
</TABLE>
and name can be any string of characters not containing a space, a left or
right parenthesis, or a comma.
Note that whitespace characters are ignored.
<P>
<B>NOTE:</B><EM>The styles <tt>tapered, striped</tt> and <tt>wedged</tt>
are only available in release 2.30 and later.</EM>
<P>
At present, the recognized style names are
"dashed", "dotted", "solid", "invis" and "bold" for nodes and edges,
"tapered" for edges only,
and "filled", "striped", "wedged", "diagonals" and "rounded" for nodes only.
The styles "filled", "striped" and "rounded" are recognized for clusters.
The style "radial" is recognized for nodes, clusters and graphs, and indicates a
radial-style gradient fill if applicable.
<P>
The style "striped" causes the
fill to be done as a set of vertical stripes. The colors are specified via a <A HREF=#k:colorList>colorList</A>, 
the colors drawn from left to right in list order. Optional color weights can be specified to indicate the
proportional widths of the bars. If the sum of the weights is less than 1, the remainder is divided evenly
among the colors with no weight. <B>Note</B>: The style "striped" is only supported with clusters and
rectangularly-shaped nodes.
<P>
The style "wedged" causes the
fill to be done as a set of wedges. The colors are specified via a <A HREF=#k:colorList>colorList</A>, 
with the colors drawn counter-clockwise starting at angle 0. Optional color weights are interpreted
analogously to the striped case described above.
<B>Note</B>: The style "wedged" is allowed only for elliptically-shaped nodes.
<P>
The following tables illustrate some of the effects of the style settings. 
Examples of tapered line styles are given below.
Examples of linear and radial gradient fill can be seen under  <A HREF=#k:colorList>colorList</A>.
<P>
  <TABLE border=1>
    <TR><TD align="center"><tt>solid</tt> <TD><IMG SRC="n_solid.png">
       <TD align="center"><tt>dashed</tt> <TD><IMG SRC="n_dashed.png">
       <TD align="center"><tt>dotted</tt> <TD><IMG SRC="n_dotted.png"> </TR>
    <TR><TD align="center"><tt>bold</tt> <TD><IMG SRC="n_bold.png">
       <TD align="center"><tt>rounded</tt> <TD><IMG SRC="n_rounded.png">
       <TD align="center"><tt>diagonals</tt> <TD><IMG SRC="n_diagonals.png"> </TR>
    <TR><TD align="center"><tt>filled</tt> <TD><IMG SRC="n_filled.png">
       <TD align="center"><tt>striped</tt> <TD><IMG SRC="n_striped.png">
       <TD align="center"><tt>wedged</tt> <TD><IMG SRC="n_wedged.png"></TR>
    <CAPTION>Basic style settings for nodes</CAPTION>
  </TABLE>
<P>
  <TABLE border=1>
    <TR><TD align="center"><tt>solid</tt> <TD><IMG SRC="e_solid.png"> 
        <TD align="center"><tt>dashed</tt> <TD><IMG SRC="e_dashed.png"> </TR>
    <TR><TD align="center"><tt>dotted</tt> <TD><IMG SRC="e_dotted.png">
        <TD align="center"><tt>bold</tt> <TD><IMG SRC="e_bold.png"></TR> <TR>
    <CAPTION>Basic style settings for edges</CAPTION>
  </TABLE>
<P>
  <TABLE border=1>
    <TR><TD align="center"><tt>solid</tt> <TD><IMG SRC="c_solid.png"> 
        <TD align="center"><tt>dashed</tt> <TD><IMG SRC="c_dashed.png">
        <TD align="center"><tt>dotted</tt> <TD><IMG SRC="c_dotted.png">
        <TD align="center"><tt>bold</tt> <TD><IMG SRC="c_bold.png"> </TR>
    <TR><TD align="center"><tt>rounded</tt> <TD><IMG SRC="c_rounded.png">
        <TD align="center"><tt>filled</tt> <TD><IMG SRC="c_filled.png">
        <TD align="center"><tt>striped</tt> <TD><IMG SRC="c_striped.png"></TR>
    <CAPTION>Basic style settings for clusters</CAPTION>
  </TABLE>
<P>
The effect of <tt>style=tapered</tt> depends on the <A HREF=#d:penwidth>penwidth</A>,
<A HREF=#d:dir>dir</A>, <A HREF=#d:arrowhead>arrowhead</A> and <A HREF=#d:arrowtail>arrowtail</A> attributes.
The edge starts with width <tt>penwidth</tt> and tapers to width 1, in points. The <tt>dir</tt> attribute
determines whether the tapering goes from tail to head (<tt>dir=forward</tt>), from head to 
tail (<tt>dir=forward</tt>), from the middle to both the head and tail (<tt>dir=both</tt>), or no
tapering at all (<tt>dir=none</tt>). If the <tt>dir</tt> is not explicitly set, the default for the
graph type is used (see <A HREF=#a:dir>dir</A>). Arrowheads and arrowtails are also drawn, based on the
value of <tt>dir</tt>; to avoid this, set <tt>arrowhead</tt> and/or <TT>arrowtail</TT> to <TT>"none"</TT>.
<P>
<B>Note:</B> At present, the tapered style only allows a simple filled polygon.
Additional styles such as <TT>dotted</TT> or <TT>dashed</TT>, or multiple colors
supplied via a <A HREF=#k:colorList>colorList</A> are ignored.
<P>
The following table illustrates the <tt>style=tapered</tt> with <tt>penwidth=7</tt> and
<tt>arrowtail=none</tt>.
  <TABLE border=1>
    <TR><TD><tt>dir</tt> &#92; <tt>arrowhead</tt><TD align="center"><tt>normal</tt><TD align="center"><tt>none</tt></TR>
    <TR><TD align="center"><tt>forward</tt> <TD><IMG SRC="normal_forward.png"> <TD><IMG SRC="none_forward.png"> </TR>
    <TR><TD align="center"><tt>back</tt> <TD><IMG SRC="normal_back.png"> <TD><IMG SRC="none_back.png"> </TR>
    <TR><TD align="center"><tt>both</tt> <TD><IMG SRC="normal_both.png"> <TD><IMG SRC="none_both.png"> </TR>
    <TR><TD align="center"><tt>none</tt> <TD><IMG SRC="normal_none.png"> <TD><IMG SRC="none_none.png"></TR>
  </TABLE>
<P>
Additional styles are available in
device-dependent form. Style lists are passed to device drivers, which
can use this to generate appropriate output.
<P>
The style attribute affects the basic appearance of nodes, edges and graphs, 
but has no effect on any text used in labels. For this, use the <A HREF=#d:fontname><TT>fontname</TT></A>, <A HREF=#d:fontsize><TT>fontsize</TT></A> and <A HREF=#d:fontcolor><TT>fontcolor</TT></A>
attributes, or the <TT>&lt;FONT&gt;</TT>, <TT>&lt;B&gt;</TT>, <TT>&lt;I&gt;</TT>, etc. 
elements in <A HREF=shapes.html#html>HTML-like labels</A>.
<P>
The <TT>setlinewidth</TT> style value can be
used for more control over the width of node borders and edges than is
allowed by <TT>bold</TT>. This style value takes an argument, specifying the
width of the line in <A HREF=#points>points</A>. For example, <TT>style="bold"</TT> is
equivalent to <TT>style="setlinewidth(2)"</TT>.
<B>The use of <TT>setlinewidth</TT> is deprecated; one should use the
<A HREF=#d:penwidth><TT>penwidth</TT></A> attribute instead.</B>
:shape
A string specifying the <A HREF=shapes.html>shape</A> of a node.
There are three
main types of shapes :
<A HREF=shapes.html#polygon>polygon-based</A>,
<A HREF=shapes.html#record>record-based</A> and
<A HREF=shapes.html#epsf>user-defined</A>.
The record-based shape has largely been superseded and greatly generalized
by <A HREF=shapes.html#html>HTML-like labels</A>. 
That is, instead of using <TT>shape=record</TT>, one might
consider using <TT>shape=none</TT> and an HTML-like label.
:startType
has the syntax <TT>(<I>style</I>)?(<I>seed</I>)?</TT>.
<P>
If <I>style</I> is present, it must be one of the strings <TT>"regular"</TT>,
<TT>"self"</TT>, or <TT>"random"</TT>. In the first case, the nodes are
placed regularly about a circle. In the second case,
an abbreviated version of neato is run to obtain the initial layout.
In the last case, the nodes are placed randomly in a unit square.
<P>
If <I>seed</I> is present, it specifies a seed for the random number
generator. If <I>seed</I> is a positive number, this is used as the
seed. If it is anything else,
the current time, and possibly the process id, is used to pick a seed,
thereby making the choice more random. In this case, the seed value
is stored in the graph.
<P>
If the value is just <TT>"random"</TT>, a time-based seed is chosen.
<P>
Note that input positions, specified by a node's
<A HREF=#d:pos>pos</A>
attribute, are only used when the style is <TT>"random"</TT>.
:viewPort
"%lf,%lf,%lf,%lf,%lf" or  "%lf,%lf,%lf,'%s'"
<P>
The viewPort <TT>W,H,Z,x,y</TT> or <TT>W,H,Z,N</TT>
specifies a viewport for the final image. The pair (W,H) gives the
dimensions (width and height) of the final image, in
<A HREF=#points>points</A>.
The optional Z is the zoom factor, i.e., the image in the original layout will be
W/Z by H/Z points in size. By default, Z is 1.
The optional last part is either a pair (x,y) giving a position in the original layout of the
graph, in
<A HREF=#points>points</A>, of the center of the viewport, or the name N
of a node whose center should used as the focus.
By default, the focus is the center of the graph bounding box, i.e.,
(bbx/2,bby/2), where "bbx,bby" is the
value of the bounding box attribute <A HREF=#a:bb>bb</A>.
<P>
Sample values: <TT>50,50,.5,'2.8 BSD'</T> or <TT>100,100,2,450,300</TT>.
The first will take the 100x100 point square centered on the node <TT>2.8 BSD</TT>
and scale it down by 0.5, yielding a 50x50 point final image.
