In the available open code you can find
a parser that builds a syntax-tree from an EBNF-like syntax notation, and
code that visits (double pass) that tree to prepare (calculate sizes) and finally draw (scaled) the diagram on a fitting <canvas>
Visualization does require HTML5 <canvas> currently. The IE impaired among us should get assistance from using something like explorercanvas.
After the war everything was in short supply. Churchill had mortgaged Great Britain and bankrupted the Treasury in order to defeat Hitler. Clothes were rationed until 1949, cheap and simple “utility furniture” until 1952, food until 1954. The rules were briefly suspended for the coronation of Elizabeth, in June 1953: everyone was allowed one extra pound of sugar and four ounces of margarine. But this exercise in supererogatory generosity served only to underscore the dreary regime of daily life.