Package Exports

turtleman
turtleman/Turtleman.js

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Readme

Turtleman

Turtleman is a JavaScript class that lets you draw SVG graphics programmatically using a "turtle graphics" paradigm, much like Logo. You can control a virtual "turtle" that moves around an SVG canvas, leaving a trail behind it. This makes it intuitive to create geometric shapes and designs.

Installation

NPM (Recommended)

npm install turtleman

Manual Installation

Download the Turtleman.js file and include it in your project.

Usage

To use Turtleman, create an instance of the Turtleman class and append its element to your HTML document. Then, you can call various methods to control the turtle's movement and drawing.

Basic Setup

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Turtleman Example</title>
    <style>
      body {
        display: flex;
        justify-content: center;
        align-items: center;
        min-height: 100vh;
        margin: 0;
        background-color: #f0f0f0;
      }
      .turtleman-container {
        border: 1px solid #ccc;
        box-shadow: 2px 2px 8px rgba(0, 0, 0, 0.1);
        position: relative;
      }
      .turtleman-container a {
        position: absolute;
        top: 10px;
        right: 10px;
        background: #007bff;
        color: white;
        padding: 5px 10px;
        text-decoration: none;
        border-radius: 3px;
        font-size: 12px;
        display: none;
      }
    </style>
  </head>
  <body>
    <div id="turtle-container"></div>

    <script type="module">
      // If using npm: import { Turtleman } from "turtleman";
      // If manual installation: import { Turtleman } from "./Turtleman.js";
      import { Turtleman } from "turtleman";

      const container = document.getElementById("turtle-container");
      const turtle = new Turtleman({
        width: 600,
        height: 400,
        startPosition: { x: 300, y: 200 },
        strokeColour: "blue",
        strokeWidth: 3,
      });

      container.appendChild(turtle.element);

      // Example drawing commands
      turtle.forward(100);
      turtle.right(90);
      turtle.forward(50);
      turtle.left(45);
      turtle.backward(70);
      turtle.pu(); // Shorthand for penup
      turtle.goto(100, 100);
      turtle.pd(); // Shorthand for pendown
    </script>
  </body>
</html>

Drawing Methods

Turtleman provides three different approaches for creating drawings, each suited for different use cases:

1. Direct Method Calls

The most straightforward approach is to call drawing methods directly on the turtle instance:

const turtle = new Turtleman();

// Draw a square
turtle.forward(100);
turtle.right(90);
turtle.forward(100);
turtle.right(90);
turtle.forward(100);
turtle.right(90);
turtle.forward(100);

// Change color and draw a triangle
turtle.strokeColour = "red";
turtle.forward(80);
turtle.right(120);
turtle.forward(80);
turtle.right(120);
turtle.forward(80);

This approach is ideal for programmatic artwork.

2. Command Strings with `drawCommands()`

const turtle = new Turtleman();

const drawingCommands = `
forward 100
right 90
forward 100
right 90
forward 100
right 90
forward 100
penup
goto 0 0
pendown
setcolor red
forward 80
right 120
forward 80
right 120
forward 80
`;

turtle.drawCommands(drawingCommands);

This approach is ideal for when you might want a serialized drawing.

3. Line Groups with `addLineGroup()`

For advanced use cases where you want to add pre-defined line segments with specific properties:

const turtle = new Turtleman();

// Define a line group object
const lineGroup = {
  points: [
    { x: 0, y: 0 },
    { x: 100, y: 0 },
    { x: 100, y: 100 },
    { x: 0, y: 100 },
    { x: 0, y: 0 },
  ],
  strokeColour: "blue", // optional
  strokeWidth: 3, // optional
};

turtle.addLineGroup(lineGroup);

// Add another line group with different properties
const triangleGroup = {
  points: [
    { x: 50, y: 50 },
    { x: 150, y: 50 },
    { x: 100, y: 150 },
    { x: 50, y: 50 },
  ],
  strokeColour: "red",
  strokeWidth: 2,
};

turtle.addLineGroup(triangleGroup);

Line Group Object Structure

The addLineGroup() method expects an object with the following properties:

points (Array, required): Array of coordinate objects { x: number, y: number }. Must have at least 2 points.
strokeColour (string, optional): Color of the lines. Defaults to the turtle's current stroke color.
strokeWidth (number, optional): Width of the lines. Defaults to the turtle's current stroke width.

This approach is ideal for:

Adding pre-computed shapes
Importing drawings from other systems
Batch operations
When you have coordinate data from external sources

4. Coordinate Capture with `startCapture()` and `endCapture()`

For scenarios where you want to collect coordinates without drawing them, use the coordinate capture feature:

const turtle = new Turtleman();

// Start capturing coordinates
turtle.startCapture();

// Move the turtle around to collect points
turtle.forward(100);
turtle.right(90);
turtle.forward(100);
turtle.right(90);
turtle.forward(100);
turtle.right(90);
turtle.forward(100);

// End capture and get the collected points
const capturedPoints = turtle.endCapture();
console.log(capturedPoints);
// Output: [
//   { x: 300, y: 200 },
//   { x: 400, y: 200 },
//   { x: 400, y: 300 },
//   { x: 300, y: 300 },
//   { x: 300, y: 200 }
// ]

// Now you can process the points or draw them differently
// For example, create a line group from the captured points
turtle.addLineGroup({
  points: capturedPoints,
  strokeColour: "purple",
  strokeWidth: 4,
});

This approach is ideal for:

Collecting coordinates for analysis
Creating shapes from captured paths
Processing coordinates before rendering
Building complex shapes from simple movements
Adding pre-computed shapes
Importing drawings from other systems
Batch operations
When you have coordinate data from external sources

API Reference

Constructor

new Turtleman(options): Creates a new Turtleman instance.
- options (Object, optional):
  - width (number, default: 500): Width of the SVG canvas.
  - height (number, default: 500): Height of the SVG canvas.
  - startPosition (Object { x, y }, default: center of canvas): Initial coordinates of the turtle.
  - heading (number, default: 0): Initial direction of the turtle.
  - penDown (boolean, default: true): Whether the pen is down for drawing.
  - strokeColour (string, default: "black"): Color of the drawn lines (e.g., "red", "#FF0000").
  - strokeWidth (number, default: 2): Thickness of the drawn lines.
  - angleType (string, default: "degrees"): "degrees" or "radians" for angle units.
  - filename (string, default: "turtleman_drawing"): Default filename for SVG downloads.
  - precision (number, default: 2): Number of decimal places for coordinate rounding.
  - mode (string, default: "contiguous"): "contiguous" or "discrete" rendering mode.

Methods

Drawing Commands

forward(distance) / fw(distance): Moves the turtle forward by distance units in the current heading.
backward(distance) / bk(distance): Moves the turtle backward by distance units.
goto(x, y) / setxy(x, y): Moves the turtle to the specified (x, y) coordinates, drawing a line if the pen is down.
moveby(x, y): Moves the turtle by the specified (x, y) offset, drawing a line if the pen is down.
jumpto(x, y) / jump(x, y): Moves the turtle to the specified (x, y) coordinates without drawing a line, regardless of pen state.
home() / hm(): Moves the turtle to its startPosition, drawing a line if the pen is down.
right(angle) / rt(angle): Turns the turtle angle units to the right (clockwise). Units depend on angleType.
left(angle) / lt(angle): Turns the turtle angle units to the left (counter-clockwise). Units depend on angleType.
setheading(angle) / seth(angle): Sets the turtle's absolute heading to angle. 0 is facing right (east). Units depend on angleType.
setPenDown(isDown): Sets the pen state. true to draw, false to not draw.
penup() / pu(): Lifts the pen (stops drawing).
pendown() / pd(): Puts the pen down (starts drawing).

Command Processing

processCommand(commandLine): Processes a single string command (e.g., "forward 100"). Used internally by drawCommands.
drawCommands(commandInput): Parses and executes a multiline string of turtle commands. Resets the turtle before drawing.

Rendering & State Management

reset(options): Resets the turtle's state to its initial configuration or new options. Clears all drawn lines.
render(): Renders all drawing commands to SVG. Called automatically when needed.
update(): Triggers a re-render of the drawing.
clearDrawing(): Clears all drawing commands and re-renders.

Advanced Drawing

addDrawingCommand(command): Adds a drawing command to the internal command array.
addLineGroup(lineGroup): Adds a group of connected lines with shared properties.
drawLine(point1, point2): Internal method to draw a line between two points.

Coordinate Capture

startCapture(): Starts capturing coordinates instead of drawing. When active, movement commands collect points in a temporary array.
endCapture(): Ends coordinate capture and returns the collected points as an array of { x, y } objects.

Download & Export

downloadSVG(): Downloads the current drawing as an SVG file.

Properties

Core Properties

element (HTMLElement): The wrapper div containing the SVG and download link. Append this to your HTML.
svg (HTMLElement): The SVG element generated by the class.
width (number): Current width of the SVG canvas.
height (number): Current height of the SVG canvas.
position (Object { x, y }): Current coordinates of the turtle.
home (Object { x, y }): The initial position set during construction or reset.
heading (number): Current heading of the turtle (normalized to 0-360 degrees or 0-2π radians).
radians (number): The current heading converted to radians (getter/setter).
penDown (boolean): Current pen state (true if drawing, false otherwise).

Styling Properties

strokeColour (string): Current stroke color for lines.
strokeWidth (number): Current stroke width for lines.
angleType (string): "degrees" or "radians".
precision (number): Number of decimal places for coordinate rounding.

Configuration Properties

mode (string): "contiguous" or "discrete" rendering mode.
filename (string): Default filename for SVG downloads.
commands (Array): Array of all drawing commands (read-only).
capturing (boolean): Whether coordinate capture mode is currently active (read-only).

Internal Properties

lineGroups (Array): Groups of connected lines for contiguous rendering mode.
needsRender (boolean): Whether the SVG needs to be re-rendered.
lineIndex (number): Current line group index.

Command String Format

The drawCommands() method accepts a multiline string with commands in the following format:

forward 100
right 90
forward 50
penup
goto 0 0
pendown
setcolor red
setwidth 3

Supported commands:

forward <distance> or fd <distance>
backward <distance> or bk <distance>
goto <x> <y> or setxy <x> <y>
jump <x> <y> or jumpto <x> <y>
home or hm
right <angle> or rt <angle>
left <angle> or lt <angle>
setheading <angle> or seth <angle>
penup or pu
pendown or pd
setcolor <color> or setcolour <color> or color <color> or colour <color> or sc <color>
setwidth <width> or width <width> or sw <width>

Rendering Modes

contiguous (default): Renders connected lines as SVG paths for better performance and smaller file sizes.
discrete: Renders each line as a separate SVG line element for more granular control.

Download Feature

The Turtleman instance automatically includes a download link that appears when you hover over the drawing area. Click it to download the current drawing as an SVG file.

turtleman