https://github.com/zonble/flutter_turtle
Turtle graphics for Flutter. It simply uses a custom painter to draw graphics by a series of Logo-like commands.
https://github.com/zonble/flutter_turtle
dart flutter graphics turtle turtle-graphics
Last synced: 6 months ago
JSON representation
Turtle graphics for Flutter. It simply uses a custom painter to draw graphics by a series of Logo-like commands.
- Host: GitHub
- URL: https://github.com/zonble/flutter_turtle
- Owner: zonble
- License: mit
- Created: 2020-01-01T14:04:34.000Z (about 6 years ago)
- Default Branch: master
- Last Pushed: 2025-07-22T15:49:40.000Z (7 months ago)
- Last Synced: 2025-08-13T06:42:43.654Z (7 months ago)
- Topics: dart, flutter, graphics, turtle, turtle-graphics
- Language: Dart
- Homepage: https://zonble.github.io/flutter_turtle/
- Size: 45.7 MB
- Stars: 49
- Watchers: 3
- Forks: 11
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
Awesome Lists containing this project
README
# flutter_turtle
[](https://pub.dev/packages/flutter_turtle)
flutter_turtle is a simple implementation of turtle graphics for Flutter. It
simply uses a custom painter to draw graphics by a series of Logo-like commands.
For further information about turtle graphics, please visit Wikipedia:
- https://en.wikipedia.org/wiki/Turtle_graphics
- https://en.wikipedia.org/wiki/Logo_(programming_language)
## Why I make this?
It is always fun to make your own [DSL](https://en.wikipedia.org/wiki/Domain-specific_language)!
## Example
A quick example:
```dart
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text(widget.title)),
body: TurtleView(
child: Container(),
commands: [
PenDown(),
SetColor((_) => Color(0xffff9933)),
SetStrokeWidth((_) => 2),
Repeat((_) => 20, [
Repeat((_) => 180, [
Forward((_) => 25.0),
Right((_) => 20),
]),
Right((_) => 18),
]),
PenUp(),
],
),
);
}
```
A Flutter web app example is available at https://zonble.github.io/flutter_turtle/
## Usage
flutter_turtle provides two class, `TurtleView`, which is your canvas and
accepts a list of commands to draw your graphics, and `AnimatedTurtleView`,
which is an animating version of `TurtleView`.
Just create an instance of `TurtleView` or `AnimatedTurtleView`, pass the
commands in the `commands` parameter, and insert it to your widget tree.
## Flutter Turtle DSL
flutter_turtle a set of Dart classes to represents commands to control your
turtle. Using them is quite alike to calling functions when you are doing turtle
graphics in Logo language, however, you are still coding in Dart and actually
composing a list of Dart objects, and then `TurtleView` runs them one by
another.
In other words, flutter_turtle built a DSL over Dart and Flutter.
If you have code in Logo like this:
``` logo
repeat 5 [ fd 100 rt 144 ]
```
It would be like the following code in Flutter Turtle DSL:
``` dart
[
Repeat((_) => 5, [
Forward((_) => 200),
Right((_) => 144),
]),
];
```
### Flow control
There are some commands help you to do flow controls. You can use the `IfElse`
class like using 'if..else..' in Dart, and you can use `Repeat` for loops.
An example of `IfElse`:
``` dart
// If it is true, go forward for 10 pixels, otherwise go back for 10 pixels.
IfElse((_)=>true, [Forward((_)=>10.0)], [Back(()=>10.0)]),
```
An example of `Repeat`:
``` dart
// Repeat 10 times.
Repeat((_)=>10, [Forward((_)=>10.0)]),
```
### Macros
Flutter Turtle DSL does not have somehow REAL functions, but somehow you can use
macros instead. You can use the `SetMacro` to add macros to your turtle:
``` dart
SetMacro('macro', [Forward((_)=>10.0)]), // A new macro named "macro".
```
Then you can use `RunMacro` to run the macro:
``` dart
RunMacro('macro', (_)=>{'arg1': 'value1', 'arg2': 'value2'}),
```
You can pass arguments while calling a macro. These arguments would be a map
sent to each Flutter Turtle command. For example:
``` dart
SetMacro('macro', [Forward((_)=>_['arg1'])]), // A new macro named "macro".
RunMacro('macro', (_)=>{'arg1': 10.0}),
```
## Commands
Currently supported commands are including:
### Turtle motion
- PenDown
- PenUp
- Left
- Right
- Forward
- Back
- SetColor
- SetStrokeWidth
- GoTo
- ResetPosition
- ResetHeading
- Label
- SetLabelHeight
### Flow control
- If
- IfElse
- Repeat
### Macros
- SetMacro
- RunMacro