LIBPACK(3)						     Library Functions Manual							LIBPACK(3)

NAME

       libpack - support for connected components

SYNOPSIS

       #include <graphviz/pack.h>

       typedef enum { l_clust, l_node, l_graph, l_array} pack_mode;

       typedef struct {
	      float aspect;	      /* desired aspect ratio */
	      int sz;			  /* row/column size size */
	      unsigned int margin; /* margin left around objects, in points */
	      int doSplines;	      /* use splines in constructing graph shape */
	      pack_mode mode;		     /* granularity and method */
	      boolean *fixed;		     /* fixed[i] == true implies g[i] should not be moved */
	      packval_t* vals;	      /* for arrays, sort numbers */
	      int flags;
       } pack_info;

       point*	  putRects(int ng, boxf* bbs, pack_info* pinfo);
       int	  packRects(int ng, boxf* bbs, pack_info* pinfo);

       point*	  putGraphs (int, Agraph_t**, Agraph_t*, pack_info*);
       int	  packGraphs (int, Agraph_t**, Agraph_t*, pack_info*);
       int	  packSubgraphs (int, Agraph_t**, Agraph_t*, pack_info*);

       pack_mode  getPackMode (Agraph_t*, pack_mode dflt);
       int	  getPack (Agraph_t*, int, int);

       int	  isConnected (Agraph_t*);
       Agraph_t** ccomps (Agraph_t*, int*, char*);
       Agraph_t** pccomps (Agraph_t*, int*, char*, boolean*);
       int	  nodeInduce (Agraph_t*);

DESCRIPTION

       libpack	supports the use of connected components in the context of laying out graphs using other graphviz libraries.  One set of functions
       can be used to take a single graph and break it apart into connected components. A complementary set of functions  takes  a  collection	of
       graphs (not necessarily components of a single graph) which have been laid out separately, and packs them together.

       As  this library is meant to be used with libcommon, it relies on the Agraphinfo_t, Agnodeinfo_t and Agedgeinfo_t used in that library. The
       specific dependencies are given below in the function descriptions.

   Creating components
     Agraph_t** ccomps (Agraph_t* g, int* cnt, char* pfx)
       The function ccomps takes a graph g and returns an array of pointers to subgraphs of g which are its connected components.  cnt is  set	to
       the  number  of	components.  If  pfx is non-NULL, it is used as a prefix for the names of the subgraphs; otherwise, the string ``_cc_'' is
       used.  Note that the subgraphs only contain the relevant nodes, not any corresponding edges. Depending on the use, this allows  the  caller
       to retrieve edge information from the root graph.

       The array returned is obtained from malloc and must be freed by the caller. The function relies on the mark field in Agnodeinfo_t.

     Agraph_t** pccomps (Agraph_t* g, int* cnt, char* pfx, boolean* pinned)
       This is identical to ccomps except that is puts all pinned nodes in the first component returned. In addition, if pinned is non-NULL, it is
       set to true if pinned nodes are found and false otherwise.

     int nodeInduce (Agraph_t* g)
       This function takes a subgraph g and finds all edges in its root graph both of whose endpoints are in g. It  returns  the  number  of  such
       edges and, if this edge is not already in the subgraph, it is added.

     int isConnected (Agraph_t* g)
       This function returns non-zero if the graph g is connected.

   Packing components
     point* putGraphs (int ng, Agraph_t** gs, Agraph_t* root, pack_info ip)
       putGraphs packs together a collection of laid out graphs into a single layout which avoids any overlap. It takes as input ng graphs gs. For
       each graph, it is assumed that all the nodes have been positioned using pos, and that the xsize and ysize fields have been set.

       If root is non-NULL, it is taken as the root graph of the subgraphs gs and is used to find the edges. Otherwise, putGraphs uses	the  edges
       found in each graph gs[i].

       For  the  modes l_node, l_clust, and l_graph, the packing is done using the polyomino-based algorithm of Freivalds et al. This allows for a
       fairly tight packing, in which a convex part of one graph might be inserted into the concave part of another.  The granularity of the poly-
       ominoes used depends on the value of ip->mode. If this is l_node, a polyomino is constructed to approximate the nodes and edges. If this is
       l_clust, the polyomino treats top-level clusters as single rectangles, unioned with the polyominoes for the remaining nodes and	edges.	If
       the value is l_graph, the polyomino for a graph is a single rectangle corresponding to the bounding box of the graph.

       The mode l_node specifies that the graphs should be packed as an array.

       If  ip->doSplines  is  true,  the function uses the spline information in the spl field of an edge, if it exists.  Otherwise, the algorithm
       represents an edge as a straight line segment connecting node centers.

       The parameter ip->margin specifies a boundary of margin points to be allowed around each node. It must be non-negative.

       The parameter ip->fixed, if non-null, should point to an array of ng booleans. If ip->fixed[i] is true, graph gs[i] should be left  at  its
       original position. The packing will first first place all of the fixed graphs, then fill in the with the remaining graphs.

       The  function returns an array of points which can be used as the origin of the bounding box of each graph. If the graphs are translated to
       these positions, none of the graph components will overlap.  The array returned is obtained from malloc and must be freed by the caller. If
       any  problem  occurs,  putGraphs  returns NULL.	As a side-effect, at its start, putGraphs sets the bb of each graph to reflect its initial
       layout. Note that putGraphs does not do any translation or change the input graphs in any other way than setting the bb.

       This function uses the bb field in Agraphinfo_t, the pos, xsize and ysize fields in nodehinfo_t and the spl field in Aedgeinfo_t.

     int packGraphs (int ng, Agraph_t** gs, Agraph_t* root, pack_info* ip)
       This function takes ng subgraphs gs of a root graph root and calls putGraphs with the given arguments to generate a  packing  of  the  sub-
       graphs. If successful, it then invokes shifts the subgraphs to their new positions. It returns 0 on success.

     int packSubgraphs (int ng, Agraph_t** gs, Agraph_t* root, pack_info* ip)
       This function simply calls packGraphs with the given arguments, and then recomputes the bounding box of the root graph.

     int pack_graph(int ng, Agraph_t** gs, Agraph_t* root, boolean* fixed)
       uses  packSubgraphs  to	place  the individual subgraphs into a single layout with the parameters obtained from getPackInfo. If successful,
       dotneato_postprocess is called on the root graph.

     point* putRects (int ng, boxf* bbs, pack_info* ip)
       putRects packs together a collection of rectangles into a single layout which avoids any overlap. It takes as input ng rectangles bbs.

       Its behavior and return value are analogous to those of putGraphs.  However, the modes l_node and l_clust are illegal.	The  fields  fixed
       and doSplines of ip are unused.

     int packRects (int ng, boxf* bbs, pack_info* ip)
       packRects is analogous to packGraphs: it calls putRects and, if this is successful, it translates the rectangles in bbs appropriately.

   Utility functions
       The library provides several functions which can be used to tailor the packing based on graph attributes.

     pack_mode parsePackModeInfo(char* p, pack_mode dflt, pack_info* pinfo)
       analyzes  p as a string representation of pack mode, storing the information in pinfo.  If p is "cluster", it returns l_clust; for "graph",
       it returns l_graph; for "node", it returns l_node; for "array", it returns l_array;  for  "aspect",  it	returns  l_aspect;  otherwise,	it
       returns dflt.  Related data is also stored in pinfo.

     pack_mode getPackModeInfo(Agraph_t * g, pack_mode dflt, pack_info* pinfo)
       This  function processes the graph's "packmode" attribute, storing the information in pinfo. It returns pinfo->mode.  The attribute is pro-
       cessed using parsePackModeInfo with dflt passed as the default argument.

     pack_mode getPackMode (Agraph_t* g, pack_mode dflt)
       This function returns a pack_mode associated with g.

     int getPack (Agraph_t* g, int not_def, int dflt)
       This function queries the graph attribute "pack". If this is defined as a non-negative integer, the integer is returned; if it  is  defined
       as "true", the value dflt is returned; otherwise, the value not_def is returned.

     pack_mode getPackInfo(Agraph_t * g, pack_mode dflt, int dfltMargin, pack_info* pinfo)
       This  function  calls  both getPackModeInfo and getPack, storing the information in pinfo. dfltMargin is used for both integer arguments of
       getPack, with the result saved as pinfo->margin.  It returns pinfo->mode.

SEE ALSO

       dot(1), neato(1), twopi(1), libgraph(3)
       K. Freivalds et al., "Disconnected Graph Layout and the Polyomino Packing Approach", GD0'01, LNCS 2265, pp. 378-391.

BUGS

       The packing does not take into account edge or graph labels.

AUTHORS

       Emden Gansner (erg@research.att.com).

								   04 APRIL 2009							LIBPACK(3)