ffgraph is a C++ class library to create, manipulate and display directed graphs. It was developed in the context of the META-Frame[SCM95] project to visualize the various data structures used in this project.
There already exist many graph-tools, so the question arises why to write a new one instead of using an existing one. Many of the existing ones are programs like GraphEd[Him90] or the VCG tool[San94] so you can use them to display data, but you have to implement a graph data structure in your programm anyway. If you use external programs to display your graphs it is often impossible to dynamically change the graph in your program and update the display, or to manipulate it graphically and pass the update back to your program. On the other hand existing graph libraries, like LEDA[Näh94] offer a powerful graph data structure, but have less powerful means for displaying the data. Other tools are specialised on a small subset of graphs, like dataflow graphs etc., and are thus not usable for us. So we decided to write a graph library on our own, which offers you a graph data structure and powerful means to display it.
Graphs consist of a set of nodes and a set of edges, where edges have exactly one target and one source. Access to the library is provided through the classes described in this paper. Graphs can be loaded and saved in a slightly extended sgraph[Him93] file format
Compare section A on page 54. The main purpose of this library is not speed or the ability to handle huge graphs, but to give an easy to use and save interface, the possibility to bind user specific data to graphs, nodes and edges and to provide a powerful and flexible mechanism to display graphs.
The library allows the user bind semantic labels to graphs, nodes, and edges. Labels are C++classes which may contain any user specific methods or data and get informed of any changes to the structure of the graph. Some labels are included in the distribution to give an example on how to use labels
E.g. there is a label implementing nested graphs included in the distribution.. Special graph labels which are subclasses of FFGraph Window may be assigned to a graph in order to display it in up to 3 dimensions. The user may provide his/her own window labels to display the graph the way it best suits his/her demands. The distribution contains window labels which display 2 or 3 dimensional graphs using the tcl/tk[Ous94] widget library for XII systems See classes FFTclBasic Window, FFTcl Window and FFTclSub Window.
To display the contens of labels, inspectors are used. The class FFclWindow contains an inspector that allows one to inspect the content of label or to invoke the inspector of a label if the label has an inspector on its own. A special interface is provided for labels that implement layout algorithms. Two layout labels implementing a 3 dimensional spring-embedder and a sugiyama layout algorithm
Written by Falk Schreiber (email@example.com)are included in the distribution.
A graph editor is included in the distribution to give an example of how to use the library.
There are several standart template container classes like sets, maps etc. included in the distribution. These classes are naively modified and debugged versions of the libg++container classes and are to be replaced soon by more efficient implementations and in some cases by better types of containers. For more information on how to use the container classes see the libg++documentation.
The library also contain a slightly modified version of a Xpm extension to tk 4.0 by Mark Crimmins (firstname.lastname@example.org) which is based on work by Harald Albrecht (email@example.com)
Ulrike Peiker, Martin Griebl