Turtle Graphics with Groovy
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Napili - Turtle Graphics with Groovy

Napili is a simple Turtle Graphics Program with Groovy as the user facing programming language. Users can control the turtle using a small set of commands, along with all the libraries that Java and Groovy have to offer.


I created Napili as a way to learn JavaFX (as well as a number of other technologies), and to better explain Groovy DSLs on my blog (which can be found at http://jamesgdriscoll.wordpress.com )

It's not a polished app (especially for someone who doesn't already know Groovy!). If you like the idea of it, and think I should spend time polishing it (up to the level, for instance, of the very good Kojo, then let me know. Any help doing so would also be appreciated.


This project has only been tested with JDK7u6, which includes JavaFX 2.2. It should work with other versions of the JDK, with JavaFX 2.2 installed and JAVAFX_HOME set, but I haven't tested it.

Build and Run

To build and run Napili, type:


Turtle Commands / Methods

  • home - send the turtle to it's home position, without drawing any lines
  • pencolor - change the color used by the turtle to draw lines. Takes javafx.scene.paint.Color as an argument.
  • penup - puts the turtle's pen in the up position - movement won't result in drawing a line.
  • pendown - puts the turtle's pen in the down position - movement results in drawing a line.
  • left - turns the turtle left, takes a numeric argument as a number of degrees (360 results in turning the turtle in a full circle counterclockwise)
  • right - turns the turtle right, takes a numeric argument as a number of degrees. (360 results in turning the turtle in a full circle clockwise)
  • forward - move the turtle forward, takes an argument that is the number of steps to move
  • back - move the turtle backward, takes an argument that is the number of steps to move
  • show - show the turtle, if hidden. Otherwise, no change.
  • hide - hide the turtle (it's still there, and will still draw, you just can't see it)
  • speed - the speed that the turtle draws. Takes one numeric argument, higher is faster

Known Bugs

There's a known bug in JavaFX on OS X 10.8, where Save / Load file invocations can crash the VM. A fairly horrific bug, but since it's only on one OS (albeit the one I use), I've left the Save / Load functionality in. This bug is already fixed in the latest JavaFX build, so the next update of JavaFX should address this.


Napili's code comes with IntelliJ IDEA and Netbeans setups, as well as the gradle setup that I use. In IDEA, just use 'gradlew idea' to create the IDEA setup, then after opening, use the default configuration to build.
In Netbeans, you may need to tweak the libraries...

Napili is named after the beautiful bay off the coast of Maui, where I once saw a turtle the size of a Volkswagen.