Chart Chisel

A tool for drawing message sequence charts.

Takes a input text file that looks like this:

entities:
  a, "Alice"
  b, "Bob"
  
arcs:
  a -> b, "Alice says hello"
  b -> a, "Bob says hi"

And generates a PNG file that looks like this:

Motivation

For a long time, I've been a user of http://www.mcternan.me.uk/mscgen/. While it is a great program it has a few limitations.

• It hasn't been updated since 2011.
• The PNG output is too low res and doesn't seem to be adjustable.
• The SVG output has different rendering bugs in every SVG renderer I can find. In Chrome, arcs with multi-line text are broken. In Microsoft Word the font kerning is bad.
• There's no way to add a title to the chart.
• It puts arrow labels too close to the arrow. As a result, text longer than the arrow covers the top half of the arrow head.
• I'd like a mode where the chart is displayed, rather than having to open it an an external viewer.
• When displaying the chart, it should continue to monitor the source file for changes. When a change is detected, the chart should be redrawn.
• The syntax of the .msc files is too verbose. MsGenny (https://github.com/sverweij/mscgen_js/blob/master/wikum/msgenny.md) seems like an improvement but lacks support for setting text and background colours. The best features of both should be combined.

Design decisions

Chart Chisel will only output PNG because the SVG problem is unfixable - different implementations are always likely to produce different rendering results.

As an experiement, the parser will be hand written instead of the Flex and Yacc system that mscgen uses. I suspect Flex and Yacc add more complexity than they remove.