graphviz.org

About

Before we launch into the gory details, we would like to explain why fonts are a hard problem. The naming and rendering of text fonts in Graphviz (and other programs) is complicated. There are several reasons: Graphviz runs on a wide range of systems: Linux and other Unix variants, Microsoft Windows, and Mac. Graphviz has a wide range of output formats: raster-oriented formats like PNG and GIF; path-based ones like Postscript, PDF and SVG; some idiosyncractic legacy formats, like troff PIC. Often, output will be downloaded and displayed on a computer or other device, different than the one where the layout was created. Graphviz layouts should be identical in size and appearance, regardless of the output format. Graphviz can run on external libraries that help with naming and rendering text fonts, but they are not required, and stripped-down Graphviz tools can be built without them. In fact, Graphviz may have to run on systems with no font files installed. There are several major font file formats to be supported. Non-Western, international character sets should be supported. Graphviz should provide a good set of standard fonts. It should be easy to specify standard fonts. Users should be able to load their own custom fonts. Output should be small to download quickly. Output should allow the best rendering possible in a given format. Output files should be easy to postprocess, for example, retaining the objects of the original graph if possible. It is very helpful to work around known bugs or missing features in support libraries and popular external tools. This is a tall order. Some of the goals conflict. Generally our approach has been to define defaults that favor convenience and good looking output, and give the user options to override the defaults.