Drawing curves with FXG is not the most intuitive thing in the world. I built this rudimentary explorer to help wrap my brain around it and as always thought it might be worth sharing. I didn’t feel like recreating the feature set of Adobe Illustrator 1.0 so you can’t add points to the path. You can only move the end-points and the control-points around. But that should be enough to see how it affects the path-data. I did go the extra centimeter and add color coding to the text output so that it would be easier to see the point groups – you’re welcome. :)
You can read all about FXG Paths at opensource.Adobe.com. In this example I'm using the "C" command to draw a cubic Bézier curve of the form: ( x1 y1 x2 y2 x y )+
Draws a cubic Bézier curve from the current point to (x,y) using (x1,y1) as the control point at the beginning of the curve and (x2,y2) as the control point at the end of the curve. C (uppercase) indicates that absolute coordinates will follow; c (lowercase) indicates that relative coordinates will follow. Multiple sets of coordinates can be specified to draw a polybézier. At the end of the command, the new current point becomes the final (x,y) coordinate pair used in the polybézier.
Check out the specification to read more about "C c S s Q q T t" commands for drawing curves.