<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
-<HTML><HEAD><TITLE>Graphviz FAQ 2005-12-27</TITLE>
+<HTML><HEAD><TITLE>Graphviz FAQ 2006-01-03</TITLE>
<META HTTP-EQUIV="content-type" CONTENT="text/html; charset=utf-8">
</HEAD><BODY>
-<H1>Graphviz FAQ 2005-12-27</H1>
+<H1>Graphviz FAQ 2006-01-03</H1>
<A HREF="mailto:north@graphviz.org">Stephen North</A>,
<A HREF="mailto:erg@graphviz.org">Emden Gansner</A>,
<h2>General</h2>
+<A name=Q1>
<B>Q. Where can I see a list of all the attributes
that control dot or neato?</B>
+</A>
<P>
See <A HREF="info/attrs.html">
Graph Attributes</A>. There is also information on
output formats</A>.
<p>
<a name="mailinglist"></a>
+<A name=Q2>
<B>Q. Where can I discuss Graphviz?</B>
+</A>
<p>
We run a mailing list.
<p>
<a href="mailto:gviz-bugs@research.att.com">gviz-bugs@research.att.com</a>.
</UL>
<p>
+<A name=Q3>
<B>Q. I'm trying to make a layout larger. How?</B>
+</A>
<p>
There are various ways to increase the size of a layout. In doing this,
one has to decide if the sizes of the nodes and text should be
Postscript environment is set up. Make sure to adjust the
<tt>BoundingBox</tt> too if your tools look at this header.
<p>
+<A name=Q4>
<B>Q. How can I join or merge certain edge routes in dot?</B>
+</A>
<p>
You can try running <tt>dot -Gconcentrate=true</tt> or you can
introduce your own virtual nodes drawn as tiny circles where
its contents have been defined. (We admit it seems desirable to define some
special syntax for non-inherited attribute settings.)
<p>
+<A name=Q5>
<B>Q. How can I draw multiple parallel edges in neato?</B>
+</A>
<p>
This is possible when the <tt>splines</tt> attribute is false, which
is the default. When <tt>splines=true</tt>, we have no good answer but
these cases, the edge
is drawn between the real nodes as usual.
<p>
+<A name=Q6>
<B>Q. Clusters are hard to see.</B>
+</A>
<P>
Set <tt>bgcolor=grey</tt>
(or some other color)
in the cluster.
<P>
+<A name=Q7>
<B>Q. How can I symmetrize (balance) tree layouts?</B>
+</A>
<P>
When a tree node has an even number of children, it isn't necessarily
centered above the two middle ones. If you know the order of the children,
<H2>Output features</H2>
+<A name=Q8>
<B>Q. How can I get high quality (antialiased) output?</B>
+</A>
<P>
The easiest thing may be to make the layout in Postscript (option <tt>-Tps</tt>),
then run through <A HREF="http://www.cs.wisc.edu/~ghost/">Ghostview</A> with
the optional <A HREF="http://www.graphviz.org/pub/graphviz/CURRENT/">graphviz-cairo</A> plugin. It is believed that Cairo
will be part of FC5, so this will become a more standard feature.
<P>
+<A name=Q9>
<B>Q. I can only get 11x17 output.</B>
+</A>
<P>
It's not us! It's probably your printer setup. If you don't
believe this, run <tt>dot -Tps</tt> and look at the
<tt>BoundingBox</tt> header. The coords are in 1/72ths of an inch.
<P>
+<A name=Q10>
<B>Q. How do I create special symbols and accents in labels?</B>
+<A name=Q2>
<P>
The following solution only works with the
raster drivers that load Truetype or Type1
handy <A HREF="http://www.research.att.com/sw/tools/graphviz/doc/char.html">
character set reference</A> .
<P>
+<A name=Q11>
<B>Q. How do I get font and color changes in record labels or other labels?</B>
+</A>
<P>
This is not possible in record shapes. However, you can do this using
<A HREF="info/shapes.html#html">
within running text in the not-too-distant future.
<P>
+<A name=Q12>
<B>Q. In plain format, splines do not touch the nodes (arrowheads are missing).</B>
+</A>
<P>
Edges are specified as the main spline and, if necessary, arrowheads
which actually abut the node. If the arrowheads are not given, drawing
Since the edges have no arrowheads, the spline specification will go
all the way to both nodes.
<P>
+<A name=Q13>
<B>Q. Record nodes are drawn differently in dot and neato when rankdir=LR.</B>
+</A>
<P>
It's true. dot -Grankdir=LR rotates record nodes so that their top level
fields are still listed across levels. rankdir=LR has no effect in neato.
<A HREF="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnhfact/html/hfactor8_5.asp">How To Avoid Foolish Consistency</A>
by Scott Berkun (Microsoft Corp.)
<P>
+<A name=Q14>
<B>Q. How can I print a big graph on multiple pages?</B>
+</A>
<P>
The <tt>page</tt> attribute, if set, tells Graphviz to print the
graph as an array of pages of the given size. Thus, the graph
a large picture and allow you to extract page-size pieces, which can
then be printed.
<P>
+<A name=Q15>
<B>Q. When I have a red edge it shows up as a
solid red in PNG and GIF formats, but has a
black border when rendered to JPEG. </B>
+</A>
<P>
This is an artifact of JPEG's lossy
compression algorithm. JPEG isn't very good
is reluctant to change anything that people
might already rely on.
<P>
+<A name=Q16>
<B>Q. How can I get custom shapes or images in my graph?</B>
+</A>
<P>
Please see the
<A HREF="http://www.graphviz.org/Documentation/html/shapehowto.html">
front end), because they don't share any universal back end structure.
We're thinking about it.
<P>
+<A name=Q17>
<B>Q. Sometimes in dotty, right mouse click shows the global menu
but none of the items can be selected.</B>
+</A>
<P>
Check that the NUMLOCK key is off. It's a
<A HREF="http://www.research.att.com/~erg/graphviz/bugs/b524.html">
known bug</A>.
<P>
+<A name=Q18>
+<B>Q. Why does dotty report a syntax error on a legal dot file?</B>
+</A>
+Typically this error is reported as:
+<pre>
+>> graph parser: syntax error near line 14
+>> context: >>> <<< digraph G {
+>> dotty.lefty: giving up on dot
+>> dotty.lefty: graph that causes dot
+>> dotty.lefty: to fail has been saved in file dottybug.dot
+</pre>
+Probably there is a command in your shell environment (such as
+.alias or .profile) that does output even for non-interactive shells.
+When this occurs, those characters go in the pipe to the dot parser
+and cause this problem. An easy check is whether other users have
+the same problem.
+<P>
+<A name=Q20>
<B>Q. How can I get some display feature (such
as bold lines) in dotty?</B>
+</A>
<P>
<A NAME="dotty_note">Dotty</A> has not really changed for many years. Therefore, there are
myriad features available in Graphviz which it cannot handle.
for someone who wants to get involved here (along with porting
dotty to GTK.)
<P>
+<A name=Q21>
<B>Q. How can I get rid of the little circles on
edges ("edge handles") in dotty?</B>
+</A>
<P>
Edit the file dotty.lefty and change the
line that says: 'edgehandles' = 1; to 'edgehandles' = 0;
it's around line 110.
<P>
+<A name=Q22>
<B>Q. I already have all the coordinates for the
nodes and edges of my graph and just want to
use dot, neato, or dotty to render it. How?</B>
+</A>
<P>
Put the graph with layout attributes into a dot
file.
normally do. All of the usual backend attributes (<TT>size</TT>,
<TT>overlap</TT>, <TT>page</TT>, etc.) are available.
<P>
+<A name=Q23>
<B>Q. I already have all the coordinates for the
nodes, and I want dot or neato to route the edges.</B>
+</A>
<P>
It's not really too convenient to use dot for this.
It is possible to use neato for this,
the nodes overlap. Since the input graph supplies fixed node positions,
it is the user's task to insure this.
<P>
+<A name=Q24>
<B>Q. I already have all the coordinates for the
nodes and edges of my graph and just want to
use dotty to render it. How?</B>
+</A>
<P>
Just run dotty on it. Dotty will use the given pos attributes.
<P>
+<A name=Q25>
<B>Q. Same as above, but I have only node coords, not edges.</B>
+</A>
<P>
<tt>neato -n -s</tt> is some help, but neato doesn't handle
spline-based parallel edges.
<P>
+<A name=Q26>
<B>Q. How can I make client-side image maps?</B>
+</A>
<P>
Use the -Tcmap command line option (only version 1.8.9 and beyond!)
<P>
+<A name=Q27>
<B>Q. Why aren't my server-side maps being recognized? I've checked the HTML!</B>
+</A>
<P>
Make sure that your server has map files enabled. For example, if running
apache, check that httpd.conf has a line like the following:
</pre>
and that it is not commented out!
<P>
+<A name=Q28>
<B>Q. I've installed Debian Graphviz and it works just fine on the command line,
but when I execute a Perl/CGI script through Apache, no output is generated.
For example, the code</B>
<B>system("/usr/local/bin/dot -Tpng /tmp/tree.dot -o /tmp/tree.png");</B>
</pre>
<B>produces no file <tt>/tmp/tree.png</tt>.</B>
+</A>
<P>
As best as we can tell, dot dies with no stdout or stderr messages on Debian
systems when run from an Apache cgi program
<A HREF="http://search.cpan.org/search?query=graphviz&mode=all">
Perl module for Graphviz</A>.
<P>
+<A name=Q29>
<B>Q. How can I get 3D output?</B>
+</A>
<P>
The Graphviz authors have qualms about the gratuitous use of 3D.
<p>
<tt>dim=3</tt> ought to be possible.
<H2>Problems</H2>
+<A name=Q30>
<B>Q. How can I avoid node overlaps in neato?</B>
+</A>
<P>
Use the graph attribute <A HREF="info/attrs.html#d:overlap"><tt>overlap</tt></A>.
<P>
+<A name=Q31>
<B>Q. How can I avoid node-edge overlaps in neato?</B>
+</A>
<P>
Use the <tt>overlap</tt> attribute to leave room among the nodes, then
use <tt>-Gsplines=true</tt>.
slows down neato, so should be used sparingly and only
with modest-sized graphs.
<P>
+<A name=Q32>
<B>Q. Neato runs forever on a certain example.</B>
+</A>
<P>
First, how big is your graph? Neato is a quadratic algorithm, roughly
equivalent to statistical multidimensional scaling. If you
is a cubic algorithm, so you would do well to avoid using <tt>splines=true</tt>.
(This commment applies to circo, fdp and twopi as well.)
<P>
+<A name=Q33>
<B>Q. Edge label placement in neato is bad.</b>
+</A>
<p>
Difficult problem. We're working on it.
If anyone has some general
label placement code (e.g. a simulated annealer based on the Marks et al.
technique in <I>Graphics Gems IV</I>), please get in touch.
<P>
+<A name=Q34>
<B>Q. Dot runs forever on a certain example.</B>
+</A>
<p>
Try dot -v to observe its progress.
<p>
The addition of <tt>attr0</tt> touches every node of the graph.
Then the addition of <tt>attr1</tt> touches every node again, and so on.
<P>
-Q. <B> Neato has unnecessary edge crossings, or has missed an
-obvious change to make a much nicer layout.</B>
+<A name=Q35>
+<B>Q. Neato has unnecessary edge crossings, or has missed an
+obvious chance to make a much nicer layout.</B>
+</A>
<P>
Neato and all similar virtual physical model algorithms rely
on heuristic solutions of optimization problems. The better
a planar layout of a planar graph, or expose all or most of a graph's
symmetries.
<P>
-Q. <B> Webdot doesn't work.</B>
+<A name=Q36>
+<B>Q. Webdot doesn't work.</B>
+</A>
<P>
We assume you're using Apache and have <A HREF="http://www.tcl.tk/">TCL</A> installed.
If you don't, it's probably better to just use the
"
(file "scaffold.tcl" line 22)
</pre>
-The above is a strong clue that webdot is not configured properly properly.
+The above is a strong clue that webdot is not configured properly.
<P>
Finally, test whether webdot runs as a cgi-bin program.
It may help to examine the cgi-bin environment using a
Save this script as .../cgi-bin/test.tcl, make it executable, then
look at: <a href="http://localhost/cgi-bin/test.tcl">http://localhost/cgi-bin/test.tcl</a>
<P>
-Q. <B> I have "Font not found" errors, or text labels missing in webdot.</B>
+<A name=Q37>
+<B>Q. I have "Font not found" errors, or text labels missing in webdot.</B>
+</A>
<P>
Firstly, recent versions of graphviz will use fontconfig if it is available
on your platform. With fontconfig, this error should not occur, so you
(or set <tt>fontpath="/your/font/directory"</tt> in every graph you lay out,
but that's pretty clumsy.)
<P>
-Q. <B> My browser doesn't recognize SVG.</B>
+<A name=Q38>
+<B>Q. My browser doesn't recognize SVG.</B>
+</A>
<P>
The correct MIME type for svg images is: <tt>image/svg+xml</tt> (note "+" not "-").
<P>
from Adobe for Windows, Linux and some other operating systems.
The <A HREF="http://www.w3.org/Amaya/">Amaya</A> browser from W3C
is said to have builtin SVG.
+Firefox 1.5 has a (a href="http://developer.mozilla.org/en/docs/SVG_in_Firefox_1.5">large subset of SVG</A> (somebody please let us know if it can
+render graphviz -Tsvg output>.
<A HREF="http://xml.apache.org/batik/">Batik</A> is an SVG
renderer in Java and can be run as a stand-alone program.
<P>
For help with embedding SVG in HTML pages, see
<A HREF="http://www.graphviz.org/webdot/svgembed.html">here</A>.
<P>
-Q. <B> libexpat is reported as containing a virus or as a security hole.
+<A name=Q39>
+<B>Q. libexpat is reported as containing a virus or as a security hole.
Is this a real problem?</B>
+</A>
<P>
No, this is a false positive reported by various security software.
See <A HREF="http://www.pcreview.co.uk/forums/thread-1689630.php">http://www.pcreview.co.uk/forums/thread-1689630.php</A> or
projects / graphviz / commitdiff