vcg(1)

NAME

VCG tool - visualization of compiler graphs

SYNOPSIS

vcg [options] [filename]
xvcg [options] [filename]

SYNOPSIS FOR SEQUENCES OF GRAPH SPECIFICATIONS

vcg -multi [options] [filename] [options] [filename] ...
xvcg -multi [options] [filename] [options] [filename] ...

DESCRIPTION

The VCG tool reads a VCG specification and visualizes the

graph. If not all positions of nodes are fixed, the tool lays

the graph out using several heuristics as reducing the number of

crossings, minimizing the size of edges, centering of nodes. The

specification language of the VCG tool is nearly compatible to

GRL, the language of the Edge tool, but contains many extensions.

The VCG tool allows folding of dynamically or statically speci

fied regions of the graph. It uses colors and runs on X11. (An

older version runs on Sunview.)

GENERAL OPTIONS

- The input is stdin instead of a file.

-h | -? Print a help message about the usage of the

tool.

-v | -version Print a version and copyright message.

-silent Be silent during the layout. No messages

or warnings are produced.

-nocolors | -blackwhite

Do not use colors on a color screen. On a

monochrom screen the graph is drawn in black & white even if it

is specified with colors. On a color screen, this mode is simu

lated, if this option is selected. The option is useful, if the

VCG tool conflicts with other programs that need colors.

-e <num> | -error <num>

Stop after <num> errors during parsing of

the specification (default: 16).

-a <num> | -animation <num>

Start the tool as animation handler. This

implies that the tool is controlled by signals (USRSIG1, USRSIG2)

from an external program. The signal USRSIG1 causes the VCG tool

to open the display window and reload its input file. The signal

USRSIG2 causes the VCG tool to close the display window. The

tool processes the input and indicates the completion of the pro

cessing to the controlling program. If <num> is greater 0, this

indication is done by sleeping <num> seconds and touching the in

put file afterwards such that its time stamp is refreshed. If

<num> is less than 0, this indication is done by sleeping - <num>

seconds and sending signal USRSIG1 to the caller process after

wards.

-m | -multi Read multiple files one after another to

display a sequence of graphs. Instead of an exit of the tool,

the next file is read. The option -multi must be specified be

fore the first input file.

-bary Use bary centering to reduce the number of

edge crossings (default).

-median Use median centering instead of bary cen

tering to reduce the number of crossings. On graphs with large

average degree of edges, bary centering might be faster.

-barymedian Use a hybrid method to reduce the number of

edge crossings. Bary centering is used for all nodes with dif

ferent bary values. For nodes with same bary values, the cross

ing reduction heuristics normally has a random effect. With this

hybrid method, the crossing reduction of nodes with same bary

values is done by median centering.

-medianbary Use a hybrid method to reduce the number of

edge crossings. Median centering is used for all nodes with dif

ferent median values. For nodes with same median values, the

crossing reduction heuristics normally has a random effect. With

this hybrid method, the crossing reduction of nodes with same me

dian values is done by bary centering.

-notune | -nofinetune

Switch the fine tuning layout phase off.

Fine tuning is a postprocessing phase after partitioning of nodes

into layers. Fine tuning changes the layers of nodes to minimize

the length of edges. If this phase is switched off, it yield a

less compact distribution of nodes in the levels.

-manhattan | -orthogonal

Switch the orthogonal manhattan layout on.

This forces edges of gradient 0 or 90 degree. The result of this

layout might be more aesthetical, if additionally the priority

layout phase with straight line tuning is used. Thus, these

phases are switched on, too, unless priority layout and straight

line tuning is switched explicitly off.

-nomanhattan | -noorthogonal

Switch the orthogonal manhattan layout ex

plicitly off.

-smanhattan Use the orthogonal manhattan layout without

separation of horizontal line segments. Horizontal line segments

are shared between different edges. This looks nice for trees

but might be confusing in general, because the location of an

edge might be ambiguously.

-nosmanhattan Switch the orthogonal manhattan layout

without separation explicitly off.

-prio Switch the priority layout on. This forces

straight long edges with gradient 90 degree during the node

placement phase. The straight line tuning phase can be used to

improve the priority layout. Thus, this phase is switched on,

too, unless straight line tuning is switched explicitly off.

-noprio Switch the priority layout explicitly off.

-straight Switch the straight line tuning phase on.

This phase forces straight long edges with gradient 90 degree. It

can be used to improve the priority layout.

-nostraight Switch the straight line tuning phase ex

plicitly off.

-nonearedge Do not allow near edges in the layout.

-l | -latelabels

Create the labels after the partitioning of

edges. This has only an effect if labels are shown in a nondirty

way. If labels are created after the partitioning of edges, the

layout will be a little bit wider and may have less crossings.

But note that sometimes this layout may also be worser than the

normal layout.

-hidesingles | -ignoresingles

Ignore single nodes (nodes without visible

edges) that are not connected with the remaining graph. These

nodes are sometimes not of interest, but would spread the layout

if they were visible.

-s | -summarize

Switch edge summary layout on. Multiple

edges between the same source and target node are summarized if

they have the same visible appearance. This reduces the number

of visible edges.

OPTIONS FOR THE LAYOUT SPEED

The speed of the layout process can be influenced by se

lecting time limits and iteration bounds of the different layout

phases. Optional layout phases can completely be skipped. But

note that we need a minimal time for each graph, in order to ini

tialize the internal data structures. Furthermore, a fast layout

is probably also an ugly layout.

-t <num> | -timelimit <num>

Set the time limit to <num> seconds of real

time. If the time limit is exceeded, the fastest possible layout

mode is switched on. This may yield a very ugly layout. Of

course, a time limit does not mean that the layout really needs

so much time: The layout may be faster, because the graph struc

ture is very simple, or it may be slower, because even the

fastest possible layout already exceeds the time limit. Further

note, that the layout depends on the real time, i.e. on the load

of the computer. Thus, given a time limit, two identical trys

need not to give identical results.

-f | -fast Switch the fast and dirty and ugly mode on.

The layout phase will be very fast, but the layout will be ugly.

This is helpful on very large graphs where aesthetic visibility

is of minor importance. The option -fast implies -bmax 2 -cmax 2

-pmax 2 -rmax 2 -smax 2.

-b <num> | -bmax <num> | -bending <num>

Set the maximal number of iterations used

for the reduction of edge bendings to <num>. Edge bendings are

used to avoid that edges are drawn across nodes. Reducing the

number of iterations results in a faster but ugly layout, i.e. to

much bendings occur. The default value is 100.

-c <num> | -cmax <num> | -crossing <num>

Set the maximal number of iterations used

for the reduction of edge crossings to <num>. The edge crossing

reduction method is called bary centering or median centering.

These may be very time consuming on large graphs. Reducing the

number of iterations results in a faster but ugly layout. As de

fault, the method is iterated as long as improvements are possi

ble.

-cmin <num> Set the minimal number of iterations used

for the reduction of edge crossings to <num>. The crossing re

duction method tries to detect improvements of the layout. If an

iteration of that method does not yield an improvment, the method

normally stops. But this situation might be a local minimum of

the quality of the layout, i.e. further iterations might find a

better layout. Thus, the minimal number of iterations can be

specified. The default value is 0.

-p <num> | -pmax <num> | -pendulum <num>

Set the maximal number of iterations used

for the balancing by the pendulum method to <num>. The pendulum

method calculates the x co-ordinates of nodes such that the lay

out is medium dense and balanced. It tries to avoid extreme gra

dients of edges. It works like a pendulum where the nodes are

the balls, the edges are the strings and uppermost nodes are

fixed on the ceiling. Reducing the number of iterations results

in a faster but ugly layout. The default value is 100.

-pmin <num> Set the minimal number of iterations used

for the balancing by the pendulum method to <num>. If an itera

tion of that method does not yield an improvment, the method nor

mally stops. But this situation might be a local minimum of the

quality of the layout, i.e. further iterations might find a bet

ter layout. Thus, the minimal number of iterations can be speci

fied. The default value is 0.

-r <num> | -rmax <num> | -rubberband <num>

Set the maximal number of iterations used

for the balancing by the rubberband method to <num>. The rub

berband method calculates the x co-ordinates of nodes such that

the nodes are centered relatively to their incoming and outgoing

edges. It works like a network where the edges pull on the nodes

like rubberbands. Reducing the number of iterations results in a

faster but ugly layout. The default value is 100.

-rmin <num> Set the minimal number of iterations used

for the balancing by the rubberband method to <num>. If an it

eration of that method does not yield an improvment, the method

normally stops. But this situation might be a local minimum of

the quality of the layout, i.e. further iterations might find a

better layout. Thus, the minimal number of iterations can be

specified. The default value is 0.

-smax <num> Set the maximal number of iterations used

for the straight line tuning phase to <num>. This phase forces

straight long edges with gradient 90 degree. It can be used to

improve the priority layout or the manhattan layout.

-nocopt | -nocopt2

Skip the optimization phase 2 during the

crossing reduction. This phase takes very long time on very

large graphs. Before reducing the number of iterations of the

crossing reduction phase (see option -cmax <num> ) you should

first try to skip this optimization phase 2.

-nocoptl | -nocoptlocal

Switch a local crossing optimization off.

This phase additionally examines pairs of edge polygons and tries

to unwind them. It slows down if the degree of the nodes is

large.

OPTIONS FOR THE DISTRIBUTION OF NODES

The quality of the layout is mainly influenced by the dis

tribution of the nodes into the hierarchy levels. Nodes of the

same level will appear in the same row. Since it depends on the

application which hierarchy is the best, there are different al

gorithms for this phase.

-d normal Normal distribution of nodes into the

levels (default). This algorithm is based on the calculation

of the strongly connected components.

-d dfs Depth first search distribution of nodes

into the levels. This is the fastest method.

-d 0 | -d minbackward

Reduce the number of backward edges heuris

tically. If the graph is acyclic, no backward edges will occur,

i.e. all edges point into the same direction.

-d + | -d maxdepth

Maximize the depth of the layout heuristi

cally. It should be used if the layout is too wide in x direc

tion. This algorithm is very fast.

-d - | -d mindepth

Minimize the depth of the layout heuristi

cally. It should be used if the layout is too wide in y direc

tion. This algorithm is very fast.

-d ++ | -d maxdepthslow

Maximize the depth of the layout heuristi

cally. See above. This algorithm is very slow, but may give bet

ter results.

-d -- | -d mindepthslow

Minimize the depth of the layout heuristi

cally. See above. This algorithm is very slow, but may give bet

ter results.

-d minindeg | -d minindegree

Prepare the nodes by sorting them according

increasing indegree (number of incoming edges). The nodes with

the minimal indegree come first. This may have various effects

on the layout.

-d maxindeg | -d maxindegree

Prepare the nodes by sorting them according

decreasing indegree. The nodes with the maximal indegree come

first. This may have various effects on the layout.

-d minoutdeg | -d minoutdegree

Prepare the nodes by sorting them according

increasing outdegree (number of outgoing edges). The nodes with

the minimal outdegree come first. This may have various effects

on the layout.

-d maxoutdeg | -d maxoutdegree

Prepare the nodes by sorting them according

decreasing outdegree. The nodes with the maximal outdegree come

first. This may have various effects on the layout.

-d mindeg | -d mindegree

Prepare the nodes by sorting them according

increasing degree (number of incoming and outgoing edges). The

nodes with the minimal degree come first. This may have various

effects on the layout.

-d maxdeg | -D maxdeg

Prepare the nodes by sorting them according

decreasing degree. The nodes with the maximal degree come first.

This may have various effects on the layout.

-d tree Use a specialized layout for trees. It does

not work with non-trees.

OPTIONS FOR THE VIEW

The view of a graph is the method of the visual appearance

of the graph in the window after the layout. Changing the view

does not require a relayout of the graph. Views are transforma

tions that are done during the drawing.

-view normal Normal view onto the graph. No distortion.

-view cfish Cartesian fisheye view. The graph is dis

torted such that the whole graph is visible. Horizontal and

vertical lines don't change their direction.

-view fcfish Cartesian fisheye view with fixed size fo

cus. The graph is distorted, but not necessarily the whole graph

is visible.

-view pfish Polar fisheye view. The graph is distort

ed such that the whole graph is visible. Even horizontal and

vertical lines might be distorted.

-view fpfish Polar fisheye view with fixed size fo

cus. The graph is distorted, but not necessarily the whole

graph is visible.

-spline Use splines instead of polygons to draw

edges. This is mainly useful if you want to export the graph into

a high quality PostScript picture. WARNING: Drawing splines is

very slow.

-nonodes Suppress drawing of nodes.

-noedges Suppress drawing of edges.

-xpos <num> Set the x-coordinate of the initial point

of the graph that appears at the window origin or of the initial

focus point to <num>.

-ypos <num> Set the y-coordinate of the initial point

of the graph that appears at the window origin or of the initial

focus point to <num>.

PRINTER DRIVER INTERFACE

The printer driver interface allows to produce an output

file of the visualized graph without the need of interaction.

The VCG tool acts as a kind of converter program in this case: it

converts a VCG file into a PostScript or bitmap file. It is rec

ommended to use the option -silent in combination to one of the

options -vcgoutput, -psoutput, -pbmoutput, or -ppmoutput. Exam

ple:

xvcg -silent -color -scale 75 -psoutput test.ps test.vcg

converts the VCG file test.vcg into a PostScript file that

contains a color picture of the graph scaled by 75 %. In this

case the interactive display is suppressed. If the graph does

not fit on the page, the output might be nonsense.

PRINTER DRIVER OPTIONS

-vcgoutput <filename>

Produce a VCG file named <filename> that

contains the graph laid out, i.e. including information about the

co-ordinates of the visible nodes. The most of the following

format options have no effect for the VCG file format.

-psoutput <filename>

Produce a PostScript file named <filename>

that contains the graph.

-pbmoutput <filename>

Produce a bitmap file named <filename> in

PBM format that contains the graph in black and white.

-ppmoutput <filename>

Produce a bitmap file named <filename> in

PPM format that contains the graph in colors.

-paper <papertype>

Select the paper type. Default is a4.

<papertype> is one of:

a4 din A4 (21 x 30 cm)
A4 din A4 (21 x 30 cm)
b5 din B5 (18.5 x 27 cm)
B5 din B5 (18.5 x 27 cm)
a5 din A5 (15 x 21 cm)
A5 din A5 (15 x 21 cm)
11x17 tabloid (11 x 17 in)
tabloid tabloid (11 x 17 in)
8x11 letter (8.5 x 11 in)
letter letter (8.5 x 11 in)
8x14 legal (8.5 x 14 in)
legal legal (8.5 x 14 in)

-noBoundingBox Suppress the calculation of a BoundingBox

(PostScript format).

-color Select a color file output. This option

works only with the PostScript format.

-grey Select a greyscaled file output. This op

tion works only with the PostScript format.

-blackwhite Select a monochromatic file output. This

is the default color. This option works only with the PostScript

format.

-portrait Select the paper orientation `Portrait'

(default).

-landscape Select the paper orientation `Landscape'.

-split <num> Split the graph into <num> pages. This op

tion works only with the PostScript format. The number of pages

must be one of 1, 4, 9, 16, or 25.

-xdpi <num> Set the horizontal resolution for the PPM

and PBM format. This allows to adapt the bitmap formats to the

resolutions of the printer.

-ydpi <num> Set the vertical resolution for the PPM and

PBM format. This allows to adapt the bitmap formats to the reso

lutions of the printer.

-scale <num> Scale the graph to <num> percent for the

file output. The default scaling fits the graph with maximal as

pect ratio to the paper size.

-width <float> <units>

Fit the graph such that its width is small

er than <float> <units>. This works only if no scaling is speci

fied. <units> are:

in Inches
inch Inches
ft Foot
foot Foot
feet Foot
mm Millimeter
cm Centimeter
dm Decimeter
m Meter

-height <float> <units>

Fit the graph such that its height is

smaller than <float> <units>. This works only if no scaling is

specified.

-lm <float> <units>

Set the left margin of the output to

<float> <units>. This works only if no right margin is speci

fied. The default position is centered on the page. In some

cases the BoundingBox of the PostScript output meight be wrong.

If a BoundingBox is needed then we recommend the options -lm 0

cm -bm 0 cm.

-rm <float> <units>

Set the right margin of the output to

<float> <units>. This works only if no left margin is specified.

The default position is centered on the page.

-tm <float> <units>

Set the top margin of the output to <float>

<units>. This works only if no bottom margin is specified. The

default position is centered on the page.

-bm <float> <units>

Set the bottom margin of the output to

<float> <units>. This works only if no top margin is specified.

The default position is centered on the page.

X11 OPTIONS

-display <host:dpy>

Set the remote X11 server to host:dpy.

This is analogous to xterm(1l).

-geometry <geom>

Specify the hint of size and location of

the X11 window. This is analogous to xterm(1l).

-bw <num> Set the border width of the X11 window to

<num> pixels. This is analogous to xterm(1l).

-font <xfont> Set the font used for messages and menu

items in the X11 window. This is analogous to xterm(1l).

-grabinputfocus

Switch setting of InputFocus on or off (de

pending on the default). Cause the VCG tool to execute a XSet

InputFocus, or to avoid to execute a XSetInputFocus on initial

ization.

GRAMMAR

The grammar of the specification language is the follow

ing:

graph

::= "graph:" '{' graph_entry_list '}'
;

graph_entry_list

::= graph_entry_list graph_entry
| graph_entry
;

graph_entry

::= graph_attribute
| node_defaults
| edge_defaults
| foldnode_defaults
| foldedge_defaults
| graph
| node
| edge
| nearedge
| bentnearedge
| backedge
;

graph_attribute

::= "title" ':' string
| "label" ':' string
| "info1" ':' string
| "info2" ':' string
| "info3" ':' string
| "color" ':' enum_color
| "textcolor" ':'enum_color
| "bordercolor" ':'enum_color
| "width" ':' integer
| "height" ':' integer
| "borderwidth" ':' integer
| 'x' ':' integer
| 'y' ':' integer
| "loc:" '{' 'x' ':' integer 'y' ':' integer '}'
| "folding" ':' integer
| "scaling" ':' float
| "shrink" ':' integer
| "stretch" ':' integer
| "textmode" ':' enum_textmode
| "shape" ':' enum_shape
| "level" ':' integer
| "vertical_order" ':' integer
| "horizontal_order" ':' integer
| "status" ':' enum_status
| "xmax" ':' integer
| "ymax" ':' integer
| "xbase" ':' integer
| "ybase" ':' integer
| "xspace" ':' integer
| "xlspace" ':' integer
| "yspace" ':' integer
| "xraster" ':' integer
| "xlraster" ':' integer
| "yraster" ':' integer
| "invisible" ':' integer
| "hidden" ':' integer
| "classname" integer ':' string
| "infoname" integer ':' string
| "colorentry" integer ':' integer integer integer
| "layoutalgorithm" ':' enum_layoutalgorithm
| "layout_downfactor" ':' integer
| "layout_upfactor" ':' integer
| "layout_nearfactor" ':' integer
| "splinefactor" ':' integer
| "late_edge_labels" ':' enum_yes_no
| "display_edge_labels" ':' enum_yes_no
| "dirty_edge_labels" ':' enum_yes_no
| "finetuning" ':' enum_yes_no
| "ignoresingles" ':' enum_yes_no
| "straight_phase" ':' enum_yes_no
| "priority_phase" ':' enum_yes_no
| "manhattan_edges" ':' enum_yes_no
| "smanhattan_edges" ':' enum_yes_no
| "nearedges" ':' enum_yes_no
| "orientation" ':' enum_orientation
| "node_alignment" ':' enum_node_align
| "port_sharing" ':' enum_yes_no
| "arrowmode" ':' enum_arrow_mode
| "spreadlevel" ':' integer
| "treefactor" ':' float
| "crossingphase2" ':' enum_yes_no
| "crossingoptimization" ':' enum_yes_no
| "crossingweight" ':' enum_cross_weight
| "view" ':' enum_view
| "edges" ':' enum_yes_no
| "nodes" ':' enum_yes_no
| "splines" ':' enum_yes_no
| "bmax" ':' integer
| "cmax" ':' integer
| "cmin" ':' integer
| "pmax" ':' integer
| "pmin" ':' integer
| "rmax" ':' integer
| "rmin" ':' integer
| "smax" ':' integer
;

enum_color

::= "aquamarine"
| "black"
| "blue"
| "cyan"
| "darkblue"
| "darkcyan"
| "darkgreen"
| "darkgrey"
| "darkmagenta"
| "darkred"
| "darkyellow"
| "gold"
| "green"
| "khaki"
| "lightblue"
| "lightcyan"
| "lightgreen"
| "lightgrey"
| "lightmagenta"
| "lightred"
| "lightyellow"
| "lilac"
| "magenta"
| "orange"
| "orchid"
| "pink"
| "purple"
| "red"
| "turquoise"
| "white"
| "yellow"
| "yellowgreen"
| integer
;

enum_orientation

::= "top_to_bottom"
| "bottom_to_top"
| "left_to_right"
| "right_to_left"
;

enum_layoutalgorithm

::=
| "tree"
| "maxdepth"
| "mindepth"
| "maxdepthslow"
| "mindepthslow"
| "maxdegree"
| "mindegree"
| "maxindegree"
| "minindegree"
| "maxoutdegree"
| "minoutdegree"
| "minbackward"
| "dfs"
;

enum_status

::= "black"
| "grey"
| "white"
;

enum_yes_no

::= "yes"
| "no"
;

enum_cross_weight

::= "bary"
| "median"
| "barymedian"
| "medianbary"
;

enum_view

::= "cfish"
| "fcfish"
| "pfish"
| "fpfish"
;

enum_arrow_mode

::= "fixed"
| "free"
;

foldnode_defaults

::= "foldnode." node_attribute
;

foldedge_defaults

::= "foldedge." edge_attribute
;

node_defaults

::= "node." node_attribute
;

edge_defaults

::= "edge." edge_attribute
;

node ::= "node:" '{' node_attribute_list '}'

;

node_attribute_list

::= node_attribute_list node_attribute
| node_attribute
;

edge ::= "edge:" '{' edge_attribute_list '}'

;

nearedge

::= "nearedge:" '{' edge_attribute_list '}'
;

bentnearedge

::= "bentnearedge:" '{' edge_attribute_list '}'
;

backedge

::= "backedge:" '{' edge_attribute_list '}'
;

edge_attribute_list

::= edge_attribute_list edge_attribute
| edge_attribute
;

node_attribute

::= "title" ':' string
| "label" ':' string
| "info1" ':' string
| "info2" ':' string
| "info3" ':' string
| "color" ':' enum_color
| "textcolor" ':'enum_color
| "bordercolor" ':'enum_color
| "width" ':' integer
| "height" ':' integer
| "borderwidth" ':' integer
| "loc:" '{' 'x' ':' integer 'y' ':' integer '}'
| "folding" ':' integer
| "scaling" ':' float
| "shrink" ':' integer
| "stretch" ':' integer
| "textmode" ':' enum_textmode
| "shape" ':' enum_shape
| "level" ':' integer
| "vertical_order" ':' integer
| "horizontal_order" ':' integer
;

enum_textmode

::= "center"
| "left_justify"
| "right_justify"
;

enum_shape

::= "box"
| "rhomb"
| "ellipse"
| "triangle"
;

enum_node_align

::= "bottom"
| "top"
| "center"
;

edge_attribute

::= "sourcename" ':' string
| "targetname" ':' string
| "label" ':' string
| "textcolor" ':'enum_color
| "color" ':' enum_color
| "thickness" ':' integer
| "class" ':' integer
| "priority" ':' integer
| "arrowcolor" ':' enum_color
| "backarrowcolor" ':' enum_color
| "arrowsize" ':' integer
| "backarrowsize" ':' integer
| "arrowstyle" ':' enum_arrowstyle
| "backarrowstyle" ':' enum_arrowstyle
| "linestyle" ':' enum_linestyle
| "anchor" ':' integer
| "horizontal_order" ':' integer
;

enum_linestyle

::= "continuous"
| "solid"
| "dotted"
| "dashed"
| "invisible"
;

enum_arrowstyle

::= none
| line
| solid
;

WARNINGS

The VCG tool needs about 200 bytes per edge and node. De

pending on the layout, it will produce a lot of additional dummy

nodes and dummy edges, such that it may run out of memory. The

layout algorithm needs exponentially time in the worst case.

ACKNOWLEDGEMENTS

The Edge tool was developed at the University of Karl

sruhe. GRL was described by S. Manke and F.N. Paulisch.
Our colleagues M. Alt and C. Ferdinand found the most bugs

and gave many proposals for improvements.
The Institute of Compiler Construction at the University

of Saarland, Germany, and the COMPARE Consortium were the first

and most important users of the VCG tool and gave us the motiva

tion, the time and many hints during the development of the tool.

SEE ALSO

Sunview(1) X11(1l) edge(l)
vcgdemomaker(l) pbmshift(l) pbmrot90(l) pbm2hp(l)
VCG - Visualization of Compiler Graphs, Design Report and

User Documentation, Ref. Compare, USAAR-1049-visual, January

1994, updated January 1995

BUGS

The X11 version has the `InputFocus' problem. This prob

lem is solved for 99 % of all cases, but may still occur.
If a graph is written to a file and reload from this file,

the layout may be different and may be ugly.
The attribute horizontal_order does only works for con

nected graphs, but not for unconnected graphs.
For some parameters, negative values are inappropriate

even if the tool does not crashes in such situations. However

the result will be very ugly. For instance, the values of xbase

and ybase should always be greater than zero.
The spline routine is still too slow and has some bugs

when exporting to a multi page PostScript file.
Currently, no further bugs are known.

AUTHORS

Georg Sander, University of Saarland, Germany.
Iris Lemke, University of Saarland, Germany.

Release 1.3 1995/01/05

VCG(1)