SYNOPSIS

#!/usr/local/bin/tclsh
package require Tcldot

USAGE

Requires the dynamic loading facilities of tcl7.6 or later.

INTRODUCTION

tcldot is a tcl dynamically loaded extension that incorporates the directed graph facilities of dot(1), and the undirected graph facilities of neato(1), into tcl and provides a set of commands to control those facilities. tcldot converts dot and neato from batch processing tools to an interpreted and, if needed, interactive set of graph manipulation facilities.

COMMANDS

tcldot initially adds only three commands to tcl, namely dotnew, dotread, and dotstring. These commands return a handle for the graph that has just been created and that handle can then be used as a command for further actions on the graph.

All other "commands" are of the form:

handle <method> parameters

Many of the methods return further handles of graphs, nodes of edges, which are themselves registered as commands.

The methods are described in detail below, but in summary:

Graph methods are:

addedge, addnode, addsubgraph, countedges, countnodes, layout, listattributes, listedgeattributes, listnodeattributes, listedges, listnodes, listnodesrev, listsubgraphs, render, rendergd, queryattributes, queryedgeattributes, querynodeattributes, queryattributevalues, queryedgeattributevalues, querynodeattributevalues, setattributes, setedgeattributes, setnodeattributes, showname, write.

Node methods are:

addedge, listattributes, listedges, listinedges, listoutedges, queryattributes, queryattributevalues, setattributes, showname.

Edge methods are:

delete, listattributes, listnodes, queryattributes, queryattributevalues, setattributes, showname.

dotnew graphType ?attributeName attributeValue? ?...?

creates a new empty graph and returns its graphHandle.

graphType can be any supported by dot(1) namely: "graph," "digraph," "graphstrict," or "digraphstrict." (In digraphs edges have a direction from tail to head. "Strict" graphs or digraphs collapse multiple edges between the same pair of nodes into a single edge.)

Following the mandatory graphType parameter the dotnew command will accept an arbitrary number of attribute name/value pairs for the graph. Certain special graph attributes and permitted values are described in dot(1), but the programmer can arbitrarily invent and assign values to additional attributes beyond these. In dot the attribute name is separated from the value by an "=" character. In tcldot the "=" has been replaced by a " " (space) to be more consistent with tcl syntax. e.g.

    set g [dotnew digraph rankdir LR]

dotread fileHandle

reads in a dot-language description of a graph from a previously opened file identified by the fileHandle. The command returns the graphHandle of the newly read graph. e.g.

    set f [open test.dot r]
    set g [dotread $f]

dotstring string

reads in a dot-language description of a graph from a Tcl string; The command returns the graphHandle of the newly read graph. e.g.

    set g [dotstring $dotsyntaxstring]

graphHandle addnode ?nodeName? ?attributeName attributeValue? ?...?

creates a new node in the graph whose handle is graphHandle and returns its nodeHandle. The handle of a node is a string like: "node0" where the integer value is different for each node. There can be an arbitrary number of attribute name/value pairs for the node. Certain special node attributes and permitted values are described in dot(1), but the programmer can arbitrarily invent and assign values to additional attributes beyond these. e.g.

    set n [$g addnode "N" label "Top\nNode" shape triangle eggs easyover]

A possible cause of confusion in tcldot is the distinction between handles, names, labels, and variables. The distinction is primarily in who owns them. Handles are owned by tcldot and are guaranteed to be unique within one interpreter session. Typically handles are assigned to variables, like "n" above, for manipulation within a tcl script. Variables are owned by the programmer. Names are owned by the application that is using the graph, typically names are important when reading in a graph from an external program or file. Labels are the text that is displayed with the node (or edge) when the graph is displayed, labels are meaningful to the reader of the graph. Only the handles and variables are essential to tcldot's ability to manipulate abstract graphs. If a name is not specified then it defaults to the string representation of the handle, if a label is not specified then it defaults to the name.

graphHandle addedge tailNode headNode ?attributeName attributeValue? ?...?

creates a new edge in the graph whose handle is graphHandle and returns its edgeHandle. tailNode and headNode can be specified either by their nodeHandle or by their nodeName. e.g.

    set n [$g addnode]
    set m [$g addnode]
    $g addedge $n $m label "NM"
    $g addnode N
    $g addnode M
    $g addedge N M label "NM"

The argument is recognized as a handle if possible and so it is best to avoid names like "node6" for nodes. If there is potential for conflict then use findnode to translate explicitly from names to handles. e.g.

    $g addnode "node6"
    $g addnode "node99"
    $g addedge [$g findnode "node6"] [$g findnode "node99"]

There can be an arbitrary number of attribute name/value pairs for the edge. Certain special edge attributes and permitted values are described in dot(1), but the programmer can arbitrarily invent and assign values to additional attributes beyond these.

graphHandle addsubgraph ?graphName? ?attributeName attributeValue? ?...?

creates a new subgraph in the graph and returns its graphHandle. If the graphName is omitted then the name of the subgraph defaults to it's graphHandle. There can be an arbitrary number of attribute name/value pairs for the subgraph. Certain special graph attributes and permitted values are described in dot(1), but the programmer can arbitrarily invent and assign values to additional attributes beyond these. e.g.

    set sg [$g addsubgraph dinglefactor 6]

Clusters, as described in dot(1), are created by giving the subgraph a name that begins with the string: "cluster". Cluster can be labelled by using the label attibute. e.g.

    set cg [$g addsubgraph cluster_A label dongle dinglefactor 6]

nodeHandle addedge headNode ?attributeName attributeValue? ?...?

creates a new edge from the tail node identified by tha nodeHandle to the headNode which can be specified either by nodeHandle or by nodeName (with preference to recognizing the argument as a handle). The graph in which this is drawn is the graph in which both nodes are members. There can be an arbitrary number of attribute name/value pairs for the edge. These edge attributes and permitted values are described in dot(1). e.g.

    [$g addnode] addedge [$g addnode] label "NM"

graphHandle delete

nodeHandle delete

edgeHandle delete

Delete all data structures associated with the graph, node or edge from the internal storage of the interpreter. Deletion of a node also results in the the deletion of all subtending edges on that node. Deletion of a graph also results in the deletion of all nodes and subgraphs within that graph (and hence all edges too). The return from these delete commands is a null string.

graphHandle countnodes

graphHandle countedges

Returns the number of nodes, or edges, in the graph.

graphHandle listedges

graphHandle listnodes

graphHandle listnodesrev

graphHandle listsubgraphs

nodeHandle listedges

nodeHandle listinedges

nodeHandle listoutedges

edgeHandle listnodes

Each return a list of handles of graphs, nodes or edges, as appropriate.

graphHandle findnode nodeName

graphHandle findedge tailnodeName headNodeName

nodeHandle findedge nodeName

Each return the handle of the item if found, or an error if none are found. For non-strict graphs when there are multiple edges between two nodes findedge will return an arbitrary edge from the set.

graphHandle showname

nodeHandle showname

edgeHandle showname

Each return the name of the item. Edge names are of the form: "a->b" where "a" and "b" are the names of the nodes and the connector "->" indicates the tail-to-head direction of the edge. In undirected graphs the connector "--" is used.

graphHandle setnodeattributes attributeName attributeValue ?...?

graphHandle setedgeattributes attributeName attributeValue ?...?

Set one or more default attribute name/values that are to apply to all nodes (edges) unless overridden by subgraphs or per-node (per-edge) attributes.

graphHandle listnodeattributes

graphHandle listedgeattributes

Return a list of attribute names.

graphHandle querynodeattributes attributeName ?...?

graphHandle queryedgeattributes attributeName ?...?

Return a list of default attribute value, one value for each of the attribute names provided with the command.

graphHandle querynodeattributes attributeName ?...?

graphHandle queryedgeattributes attributeName ?...?

Return a list of pairs of attrinute name and default attribute value, one pair for each of the attribute names provided with the command.

graphHandle setattributes attributeName attributeValue ?...?

nodeHandle setattributes attributeName attributeValue ?...?

edgeHandle setattributes attributeName attributeValue ?...?

Set one or more attribute name/value pairs for a specific graph, node, or edge instance.

graphHandle listattributes

nodeHandle listattributes

edgeHandle listattributes

Return a list of attribute names (attribute values are provided by queryattribute

graphHandle queryattributes attributeName ?...?

nodeHandle queryattributes attributeName ?...?

edgeHandle queryattributes attributeName ?...?

Return a list of attribute value, one value for each of the attribute names provided with the command.

graphHandle queryattributevalues attributeName ?...?

nodeHandle queryattributevalues attributeName ?...?

edgeHandle queryattributevalues attributeName ?...?

Return a list of pairs or attribute name and attribute value, one value for each of the attribute names provided with the command.

graphHandle layout ?dot|neato|circo|twopi|fdp|nop?

Annotate the graph with layout information. This commands takes an abstract graph add shape and position information to it according to the layout engine's rules of eye-pleasing graph layout. If the layout engine is unspecified then it defaults to dot for directed graphs, and neato otherwise. If the nop engine is specified then layout infomation from the input graph is used. The result of the layout is stored as additional attributes name/value pairs in the graph, node and edges. These attributes are intended to be interpreted by subsequent write or render commands.

graphHandle write fileHandle format ?dot|neato|circo|twopi|fdp|nop?

Write a graph to the open file represented by fileHandle in a specific format. Possible formats are: "ps" "mif" "hpgl" "plain" "dot" "gif" "ismap" If the layout hasn't been already done, then it will be done as part of this operation using the same rules for selecting the layout engine as for the layout command.

graphHandle rendergd gdHandle

Generates a rendering of a graph to a new or existing gifImage structure (see gdTcl(1) ). Returns the gdHandle of the image. If the layout hasn't been already done, then it will be done as part of this operation using the same rules for selecting the layout engine as for the layout command.

graphHandle render ?canvas ?dot|neato|circo|twopi|fdp|nop??

If no canvas argument is provided then render returns a string of commands which, when evaluated, will render the graph to a Tk canvas whose canvasHandle is available in variable $c

If a canvas argument is provided then render produces a set of commands for canvas instead of $c.

If the layout hasn't been already done, then it will be done as part of this operation using the same rules for selecting the layout engine as for the layout command.

    #!/usr/local/bin/wish
    package require Tcldot
    set c [canvas .c]
    pack $c
    set g [dotnew digraph rankdir LR]
    $g setnodeattribute style filled color white
    [$g addnode Hello] addedge [$g addnode World!]
    $g layout
    if {[info exists debug]} {
        puts [$g render]         ;# see what render produces
    }
    eval [$g render]

Render generates a series of canvas commands for each graph element, for example a node typically consist of two items on the canvas, one for the shape and the other for the label. The canvas items are automatically tagged (See canvas(n) ) by the commands generated by render. The tags take one of two forms: text items are tagged with 0<handle> and shapes and lines are rendered with 1<handle>.

The tagging can be used to recognize when a user wants to interact with a graph element using the mouse. See the script in examples/disp of the tcldot distribution for a demonstration of this facility.

AUTHOR

John Ellson ([email protected])

ACKNOWLEDGEMENTS

John Ousterhout, of course, for tcl and tk. Steven North and Eleftherios Koutsofios for dot. Karl Lehenbauer and Mark Diekhans of NeoSoft for the handles.c code which was derived from tclXhandles.c. Tom Boutell of the Quest Center at Cold Spring Harbor Labs for the gif drawing routines. Spencer Thomas of the University of Michigan for gdTcl.c. Dayatra Shands for coding much of the initial implementation of tcldot.

KEYWORDS

graph, tcl, tk, dot, neato.