dot+user+guide

Drawing graphs with dot Emden Gansner and Eleftherios Koutsofios and Stephen North January 26, 2006 Abstract dot draws directed graphs as hierarchies. It runs as a command line pro- gram, web visualization service, or with a compatible graphical interface. Its features include well-tuned layout algorithms for placing nodes and edge splines, edge labels, “record” shapes with “ports” for drawing data struc- tures; cluster layouts; and an underlying file language for stream-oriented graph tools. Below is a reduced module dependency graph of an SML-NJ compiler that took 0.98 seconds of user time on a 1.4 Ghz AMD Athlon. ContMap FreeMap Expand CPSprint Coder BaseCoder ErrorMsg SparcInstr GlobalFix CPS Hoist SortedList Intset CPSopt Contract Eta Closure Profile List2 SparcAsCode SparcMCEmit IEEEReal SparcCM CG SparcMCode ClosureCallee Sort SparcAsEmit Spill PrintUtil CPSsize Prim SparcMC CPScomp Access RealConst SparcAC Convert CoreInfo Lambda CPSgen Strs Signs AbstractFct ApplyFunctor Overload PrintType Unify Typecheck PrintAbsyn Stream MLLexFun Vector Ascii LrParserJoinWithArg Join MLLrValsFun CoreLang NewParse Index Misc TyvarSet Absyn Types Normalize Modules ConRep Instantiate LrTable Backpatch PrimTypes PolyCont Initial Assembly Math Unsafe Loader CInterface CleanUp CoreFunc InLine Fastlib CoreDummy Overloads MakeMos Stamps IntmapPersStamps Pathnames Symbol Bigint Dynamic IntStrMap ArrayExt UnionfindSiblings StrgHash Env BasicTypes Tuples ModuleUtil EqTypes Fixity TypesUtil Equal Variables BareAbsyn PrintBasics PrintVal PrintDec SigMatch IntSparcD IntShare BatchRealDebug BogusDebug UnixPaths Interact ModuleComp Importer IntSparcIntNullD Linkage Prof IntNull Interp ProcessFile FreeLvar LambdaOpt Translate OptReorder CompSparc MCopt MCprint Nonrec MC InlineOps Unboxed 1 dot User’s Manual, January 26, 2006 2 1 Basic Graph Drawing dot draws directed graphs. It reads attributed graph text files and writes drawings, either as graph files or in a graphics format such as GIF, PNG, SVG or PostScript (which can be converted to PDF). dot draws a graph in four main phases. Knowing this helps you to understand what kind of layouts dot makes and how you can control them. The layout proce- dure used by dot relies on the graph being acyclic. Thus, the first step is to break any cycles which occur in the input graph by reversing the internal direction of certain cyclic edges. The next step assigns nodes to discrete ranks or levels. In a top-to-bottom drawing, ranks determine Y coordinates. Edges that span more than one rank are broken into chains of “virtual” nodes and unit-length edges. The third step orders nodes within ranks to avoid crossings. The fourth step sets X coordi- nates of nodes to keep edges short, and the final step routes edge splines. This is the same general approach as most hierarchical graph drawing programs, based on the work of Warfield [War77], Carpano [Car80] and Sugiyama [STT81]. We refer the reader to [GKNV93] for a thorough explanation of dot’s algorithms. dot accepts input in the DOT language (cf. Appendix A). This language de- scribes three kinds of objects: graphs, nodes, and edges. The main (outermost) graph can be directed (digraph) or undirected graph. Because dot makes lay- outs of directed graphs, all the following examples use digraph. (A separate layout utility, neato, draws undirected graphs [Nor92].) Within a main graph, a subgraph defines a subset of nodes and edges. Figure 1 is an example graph in the DOT language. Line 1 gives the graph name and type. The lines that follow create nodes, edges, or subgraphs, and set attributes. Names of all these objects may be C identifiers, numbers, or quoted C strings. Quotes protect punctuation and white space. A node is created when its name first appears in the file. An edge is created when nodes are joined by the edge operator ->. In the example, line 2 makes edges from main to parse, and from parse to execute. Running dot on this file (call it graph1.dot) $ dot -Tps graph1.dot -o graph1.ps yields the drawing of Figure 2. The command line option -Tps selects PostScript (EPSF) output. graph1.ps may be printed, displayed by a PostScript viewer, or embedded in another document. It is often useful to adjust the representation or placement of nodes and edges in the layout. This is done by setting attributes of nodes, edges, or subgraphs in the input file. Attributes are name-value pairs of character strings. Figures 3 and 4 illustrate some layout attributes. In the listing of Figure 3, line 2 sets the graph’s dot User’s Manual, January 26, 2006 3 1: digraph G { 2: main -> parse -> execute; 3: main -> init; 4: main -> cleanup; 5: execute -> make_string; 6: execute -> printf 7: init -> make_string; 8: main -> printf; 9: execute -> compare; 10: } Figure 1: Small graph main parse init cleanup printf execute make_string compare Figure 2: Drawing of small graph dot User’s Manual, January 26, 2006 4 size to 4,4 (in inches). This attribute controls the size of the drawing; if the drawing is too large, it is scaled as necessary to fit. Node or edge attributes are set off in square brackets. In line 3, the node main is assigned shape box. The edge in line 4 is straightened by increasing its weight (the default is 1). The edge in line 6 is drawn as a dotted line. Line 8 makes edges from execute to make string and printf. In line 10 the default edge color is set to red. This affects any edges created after this point in the file. Line 11 makes a bold edge labeled 100 times. In line 12, node make_string is given a multi-line label. Line 13 changes the default node to be a box filled with a shade of blue. The node compare inherits these values. 2 Drawing Attributes The complete list of attributes that affect graph drawing is summarized in Tables 1, 2 and 3. 2.1 Node Shapes Nodes are drawn, by default, with shape=ellipse, width=.75, height=.5 and labeled by the node name. Other common shapes include box, circle, record and plaintext. A complete list of node shapes is given in Appendix E. The node shape plaintext is of particularly interest in that it draws a node with- out any outline, an important convention in some kinds of diagrams. In cases where the graph structure is of main concern, and especially when the graph is moderately large, the point shape reduces nodes to display minimal content. When drawn, a node’s actual size is the greater of the requested size and the area needed for its text label, unless fixedsize=true, in which case the width and height values are enforced. Node shapes fall into two broad categories: polygon-based and record-based.1 All node shapes except record and Mrecord are considered polygonal, and are modeled by the number of sides (ellipses and circles being special cases), and a few other geometric properties. Some of these properties can be specified in a graph. If regular=true, the node is forced to be regular. The parameter peripheries sets the number of boundary curves drawn. For example, a dou- blecircle has peripheries=2. The orientation attribute specifies a clock- wise rotation of the polygon, measured in degrees. 1There is a way to implement custom node shapes, using shape=epsf and the shapefile attribute, and relying on PostScript output. The details are beyond the scope of this user’s guide. Please contact the authors for further information. dot User’s Manual, January 26, 2006 5 1: digraph G { 2: size ="4,4"; 3: main [shape=box]; /* this is a comment */ 4: main -> parse [weight=8]; 5: parse -> execute; 6: main -> init [style=dotted]; 7: main -> cleanup; 8: execute -> { make_string; printf} 9: init -> make_string; 10: edge [color=red]; // so is this 11: main -> printf [style=bold,label="100 times"]; 12: make_string [label="make a\nstring"]; 13: node [shape=box,style=filled,color=".7 .3 1.0"]; 14: execute -> compare; 15: } Figure 3: Fancy graph main parse init cleanup printf 100 times execute make a stringcompare Figure 4: Drawing of fancy graph dot User’s Manual, January 26, 2006 6 The shape polygon exposes all the polygonal parameters, and is useful for creating many shapes that are not predefined. In addition to the parameters regular, peripheries and orientation, mentioned above, polygons are parameter- ized by number of sides sides, skew and distortion. skew is a floating point number (usually between −1.0 and 1.0) that distorts the shape by slanting it from top-to-bottom, with positive values moving the top of the polygon to the right. Thus, skew can be used to turn a box into a parallelogram. distortion shrinks the polygon from top-to-bottom, with negative values causing the bottom to be larger than the top. distortion turns a box into a trapezoid. A variety of these polygonal attributes are illustrated in Figures 6 and 5. Record-based nodes form the other class of node shapes. These include the shapes record and Mrecord. The two are identical except that the latter has rounded corners. These nodes represent recursive lists of fields, which are drawn as alternating horizontal and vertical rows of boxes. The recursive structure is determined by the node’s label, which has the following schema: rlabel → field ( ’|’ field )* field → boxLabel | ’’ rlabel ’’ boxLabel → [ ’<’ string ’>’ ] [ string ] Literal braces, vertical bars and angle brackets must be escaped. Spaces are interpreted as separators between tokens, so they must be escaped if they are to appear literally in the text. The first string in a boxLabel gives a name to the field, and serves as a port name for the box (cf. Section 3.1). The second string is used as a label for the field; it may contain the same escape sequences as multi-line labels (cf. Section 2.2. The example of Figures 7 and 8 illustrates the use and some properties of records. 2.2 Labels As mentioned above, the default node label is its name. Edges are unlabeled by default. Node and edge labels can be set explicitly using the label attribute as shown in Figure 4. Though it may be convenient to label nodes by name, at other times labels must be set explicitly. For example, in drawing a file directory tree, one might have several directories named src, but each one must have a unique node identifier. The inode number or full path name are suitable unique identifiers. Then the label of each node can be set to the file name within its directory. dot User’s Manual, January 26, 2006 7 1: digraph G { 2: a -> b -> c; 3: b -> d; 4: a [shape=polygon,sides=5,peripheries=3,color=lightblue,style=filled]; 5: c [shape=polygon,sides=4,skew=.4,label="hello world"] 6: d [shape=invtriangle]; 7: e [shape=polygon,sides=4,distortion=.7]; 8: } Figure 5: Graph with polygonal shapes a b hello world d e Figure 6: Drawing of polygonal node shapes 1: digraph structs { 2: node [shape=record]; 3: struct1 [shape=record,label=" left| mid\ dle| right"]; 4: struct2 [shape=record,label=" one| two"]; 5: struct3 [shape=record,label="hello\nworld |{ b |{c| d|e}| f}| g | h"]; 6: struct1 -> struct2; 7: struct1 -> struct3; 8: } Figure 7: Records with nested fields zp 高亮 zp 文本框 默认形状是椭圆 dot User’s Manual, January 26, 2006 8 Multi-line labels can be created by using the escape sequences \n, \l, \r to terminate lines that are centered, or left or right justified.2 Graphs and cluster subgraphs may also have labels. Graph labels appear, by default, centered below the graph. Setting labelloc=t centers the label above the graph. Cluster labels appear within the enclosing rectangle, in the upper left corner. The value labelloc=b moves the label to the bottom of the rectangle. The setting labeljust=r moves the label to the right. The default font is 14-point Times-Roman, in black. Other font families, sizes and colors may be selected using the attributes fontname, fontsize and fontcolor. Font names should be compatible with the target interpreter. It is best to use only the standard font families Times, Helvetica, Courier or Symbol as these are guaranteed to work with any target graphics language. For example, Times-Italic, Times-Bold, and Courier are portable; AvanteGarde- DemiOblique isn’t. For bitmap output, such as GIF or JPG, dot relies on having these fonts avail- able during layout. Most precompiled installations of Graphviz use the fontconfig library for matching font names to available fontfiles. fontconfig comes with a set of utilities for showing matches and installing fonts. Please refer to the font- config documentation, or the external Graphviz FontFAQ or for further details. If Graphviz is built without fontconfig (which usually means you compiled it from source code on your own), the fontpath attribute can specify a list of directo- ries3 which should be searched for the font files. If this is not set, dot will use the DOTFONTPATH environment variable or, if this is not set, the GDFONTPATH environment variable. If none of these is set, dot uses a built-in list. Edge labels are positioned near the center of the edge. Usually, care is taken to prevent the edge label from overlapping edges and nodes. It can still be difficult, in a complex graph, to be certain which edge a label belongs to. If the decorate attribute is set to true, a line is drawn connecting the label to its edge. Sometimes avoiding collisions among edge labels and edges forces the drawing to be bigger than desired. If labelfloat=true, dot does not try to prevent such overlaps, allowing a more compact drawing. An edge can also specify additional labels, using headlabel and taillabel, which are be placed near the ends of the edge. The characteristics of these la- bels are specified using the attributes labelfontname, labelfontsize and labelfontcolor. These labels are placed near the intersection of the edge and the node and, as such, may interfere with them. To tune a drawing, the user can set 2The escape sequence \N is an internal symbol for node names. 3For Unix-based systems, this is a concatenated list of pathnames, separated by colons. For Windows-based systems, the pathnames are separated by semi-colons. dot User’s Manual, January 26, 2006 9 the labelangle and labeldistance attributes. The former sets the angle, in degrees, which the label is rotated from the angle the edge makes incident with the node. The latter sets a multiplicative scaling factor to adjust the distance that the label is from the node. 2.3 Graphics Styles Nodes and edges can specify a color attribute, with black the default. This is the color used to draw the node’s shape or the edge. A color value can be a hue- saturation-brightness triple (three floating point numbers between 0 and 1, sepa- rated by commas); one of the colors names listed in Appendix G (borrowed from some version of the X window system); or a red-green-blue (RGB) triple4 (three hexadecimal number between 00 and FF, preceded by the character ’#’). Thus, the values "orchid", "0.8396,0.4862,0.8549" and "#DA70D6" are three ways to specify the same color. The numerical forms are convenient for scripts or tools that automatically generate colors. Color name lookup is case-insensitive and ignores non-alphanumeric characters, so warmgrey and Warm_Grey are equiv- alent. We can offer a few hints regarding use of color in graph drawings. First, avoid using too many bright colors. A “rainbow effect” is confusing. It is better to choose a narrower range of colors, or to vary saturation along with hue. Sec- ond, when nodes are filled with dark or very saturated colors, labels seem to be more readable with fontcolor=white and fontname=Helvetica. (We also have PostScript functions for dot that create outline fonts from plain fonts.) Third, in certain output formats, you can define your own color space. For exam- ple, if using PostScript for output, you can redefine nodecolor, edgecolor, or graphcolor in a library file. Thus, to use RGB colors, place the following line in a file lib.ps. /nodecolor {setrgbcolor} bind def Use the -l command line option to load this file. dot -Tps -l lib.ps file.dot -o file.ps The style attribute controls miscellaneous graphics features of nodes and edges. This attribute is a comma-separated list of primitives with optional argu- ment lists. The predefined primitives include solid, dashed, dotted, bold and invis. The first four control line drawing in node boundaries and edges 4A fourth form, RGBA, is also supported, which has the same format as RGB with an additional fourth hexadecimal number specifying alpha channel or transparency information. dot User’s Manual, January 26, 2006 10 Name Default Values color black node shape color comment any string (format-dependent) distortion 0.0 node distortion for shape=polygon fillcolor lightgrey/black node fill color fixedsize false label text has no affect on node size fontcolor black type face color fontname Times-Roman font family fontsize 14 point size of label group name of node’s group height .5 height in inches label node name any string layer overlay range all, id or id:id orientation 0.0 node rotation angle peripheries shape-dependent number of node boundaries regular false force polygon to be regular shape ellipse node shape; see Section 2.1 and Appendix E shapefile external EPSF or SVG custom shape file sides 4 number of sides for shape=polygon skew 0.0 skewing of node for shape=polygon style graphics options, e.g. bold, dotted, filled; cf. Section 2.3 URL URL associated with node (format-dependent) width .75 width in inches z 0.0 z coordinate for VRML output Table 1: Node attributes dot User’s Manual, January 26, 2006 11 Name Default Values arrowhead normal style of arrowhead at head end arrowsize 1.0 scaling factor for arrowheads arrowtail normal style of arrowhead at tail end color black edge stroke color comment any string (format-dependent) constraint true use edge to affect node ranking decorate if set, draws a line connecting labels with their edges dir forward forward, back, both, or none fontcolor black type face color fontname Times-Roman font family fontsize 14 point size of label headlabel label placed near head of edge headport n,ne,e,se,s,sw,w,nw headURL URL attached to head label if output format is ismap label edge label labelangle -25.0 angle in degrees which head or tail label is rotated off edge labeldistance 1.0 scaling factor for distance of head or tail label from node labelfloat false lessen constraints on edge label placement labelfontcolor black type face color for head and tail labels labelfontname Times-Roman font family for head and tail labels labelfontsize 14 point size for head and tail labels layer overlay range all, id or id:id lhead name of cluster to use as head of edge ltail name of cluster to use as tail of edge minlen 1 minimum rank distance between head and tail samehead tag for head node; edge heads with the same tag are merged onto the same port sametail tag for tail node; edge tails with the same tag are merged onto the same port style graphics options, e.g. bold, dotted, filled; cf. Section 2.3 taillabel label placed near tail of edge tailport n,ne,e,se,s,sw,w,nw tailURL URL attached to tail label if output format is ismap weight 1 integer cost of stretching an edge Table 2: Edge attributes dot User’s Manual, January 26, 2006 12 Name Default Values bgcolor background color for drawing, plus initial fill color center false center drawing on page clusterrank local may be global or none color black for clusters, outline color, and fill color if fillcolor not defined comment any string (format-dependent) compound false allow edges between clusters concentrate false enables edge concentrators fillcolor black cluster fill color fontcolor black type face color fontname Times-Roman font family fontpath list of directories to search for fonts fontsize 14 point s