The ruby direction/way to draw vector and export to pdf?

Simply put, my app needs to draw something(music notation) on a canvas and I want to be able to export the drawing to pdf file. Not as picture but sharp vector drawing. I only need to be able to draw lines, oval and rectangle.
I created previously a app in tkinter which can export to postscript but can’t export to pdf so you need to do all kinds of tricks to make pdf export. Is there a gui library that supports this(less or more) out of the box? The problem I with tkinter canvas is that you can’t build(at least I didn’t succeed) a native way to export the drawing to pdf. You always depend on something that needs to be installed on the system.
(didn’t write this in ruby but it is the project I am talking about; want to learn ruby, looks awesome :sunglasses:)
How to:

  • Draw to canvas? (which library’s can I choose from?)
  • Export drawing to PDF in a independent way?

For exporting to PDF, does Prawn do what you want? It writes pdf directly: File: README — Prawn Documentation