Documentation Site

Flame’s documentation is written in Markdown. It is then rendered into HTML with the help of the Sphinx engine and its MyST plugin. The rendered files are then manually (but with the help of a script) published to flame-docs-site, where the site is served via GitHub Pages.


The main documentation site is written in Markdown. We assume that you’re already familiar with the basics of the Markdown syntax (if not, there are plenty of guides on the Internet). Instead, this section will focus on the Markdown extensions that are enabled in our build system.

Table of contents

The table of contents for the site must be created manually. This is done using special {toctree} blocks, one per each subdirectory:


First Topic    <relative_path/>
Second Topic   <>

When adding new documents into the documentation site, make sure that they are mentioned in one of the toctrees – otherwise you will see a warning during the build that the document is orphaned.


Admonitions are emphasized blocks of text with a distinct appearance. They are created using the triple-backticks syntax:

Please note this very important caveat.
Don't look down, or you will encounter an error.
I told you so.
Also check out this cool thingy.


Please note this very important caveat.


Don’t look down, or you will encounter an error.


I told you so.

See also

Also check out this cool thingy.


The special {deprecated} block can be used to mark some part of documentation or syntax as being deprecated. This block requires specifying the version when the deprecation has occurred

```{deprecated} v1.3.0

Please use this **other** thing instead.

Which would be rendered like this:

Deprecated since version v1.3.0: Please use this other thing instead.

Live examples

Our documentation site includes a custom-built flutter-app directive which allows creating Flutter widgets and embedding them alongside the overall documentation content.

In Markdown, the code for inserting an embed looks like this:

:sources: ../flame/examples
:page: tap_events
:show: widget code popup
:width: 180
:height: 160

Here’s what the different options mean:

  • sources: specifies the name of the root directory where the Flutter code that you wish to run is located. This directory must be a Flutter repository, and there must be a pubspec.yaml file there. The path is considered relative to the doc/_sphinx directory.

  • page: a sub-path within the root directory given in sources. This option has two effects: first, it is appended to the path of the html page of the widget, like so: main.dart.html?$page. Secondly, the button to show the source code of the embed will display the code from the file or directory with the name given by page.

    The purpose of this option is to be able to bundle multiple examples into a single executable. When using this option, the main.dart file of the app should route the execution to the proper widget according to the page being passed.

  • show: contains a subset of modes: widget, code, infobox, and popup. The widget mode creates an iframe with the embedded example, directly within the page. The code mode will show a button that allows the user to see the code that produced this example. The popup mode also shows a button, which displays the example in an overlay window. This is more suitable for demoing larger apps. Using both “widget” and “popup” modes at the same time is not recommended. Finally, the infobox mode will display the result in a floating window – this mode is best combined with widget and code.

  • width: an integer that defines the width of the embedded application. If this is not defined, the width will be 100%.

  • height: an integer that defines the height of the embedded application. If this is not defined, the height will be 350px.

  1import 'dart:math';
  3import 'package:flame/components.dart';
  4import 'package:flame/events.dart';
  5import 'package:flame/game.dart';
  6import 'package:flutter/rendering.dart';
  8class TapEventsGame extends FlameGame {
  9  @override
 10  Future<void> onLoad() async {
 11    add(TapTarget());
 12  }
 15/// This component is the tappable blue-ish rectangle in the center of the game.
 16/// It uses the [TapCallbacks] mixin to receive tap events.
 17class TapTarget extends PositionComponent with TapCallbacks {
 18  TapTarget() : super(anchor:;
 20  final _paint = Paint()..color = const Color(0x448BA8FF);
 22  /// We will store all current circles into this map, keyed by the `pointerId`
 23  /// of the event that created the circle.
 24  final Map<int, ExpandingCircle> _circles = {};
 26  @override
 27  void onGameResize(Vector2 size) {
 28    super.onGameResize(size);
 29    this.size = size - Vector2(100, 75);
 30    if (this.size.x < 100 || this.size.y < 100) {
 31      this.size = size * 0.9;
 32    }
 33    position = size / 2;
 34  }
 36  @override
 37  void render(Canvas canvas) {
 38    canvas.drawRect(size.toRect(), _paint);
 39  }
 41  @override
 42  void onTapDown(TapDownEvent event) {
 43    final circle = ExpandingCircle(event.localPosition);
 44    _circles[event.pointerId] = circle;
 45    add(circle);
 46  }
 48  @override
 49  void onLongTapDown(TapDownEvent event) {
 50    _circles[event.pointerId]!.accent();
 51  }
 53  @override
 54  void onTapUp(TapUpEvent event) {
 55    _circles.remove(event.pointerId)!.release();
 56  }
 58  @override
 59  void onTapCancel(TapCancelEvent event) {
 60    _circles.remove(event.pointerId)!.cancel();
 61  }
 64class ExpandingCircle extends Component {
 65  ExpandingCircle(this._center)
 66      : _baseColor =
 67            HSLColor.fromAHSL(1, random.nextDouble() * 360, 1, 0.8).toColor();
 69  final Color _baseColor;
 70  final Vector2 _center;
 71  double _outerRadius = 0;
 72  double _innerRadius = 0;
 73  bool _released = false;
 74  bool _cancelled = false;
 75  late final _paint = Paint()
 76 = PaintingStyle.stroke
 77    ..color = _baseColor;
 79  /// "Accent" is thin white circle generated by `onLongTapDown`. We use
 80  /// negative radius to indicate that the circle should not be drawn yet.
 81  double _accentRadius = -1e10;
 82  late final _accentPaint = Paint()
 83 = PaintingStyle.stroke
 84    ..strokeWidth = 0
 85    ..color = const Color(0xFFFFFFFF);
 87  /// At this radius the circle will disappear.
 88  static const maxRadius = 175;
 89  static final random = Random();
 91  double get radius => (_innerRadius + _outerRadius) / 2;
 93  void release() => _released = true;
 94  void cancel() => _cancelled = true;
 95  void accent() => _accentRadius = 0;
 97  @override
 98  void render(Canvas canvas) {
 99    canvas.drawCircle(_center.toOffset(), radius, _paint);
100    if (_accentRadius >= 0) {
101      canvas.drawCircle(_center.toOffset(), _accentRadius, _accentPaint);
102    }
103  }
105  @override
106  void update(double dt) {
107    if (_cancelled) {
108      _innerRadius += dt * 100; // implosion
109    } else {
110      _outerRadius += dt * 20;
111      _innerRadius += dt * (_released ? 20 : 6);
112      _accentRadius += dt * 20;
113    }
114    if (radius >= maxRadius || _innerRadius > _outerRadius) {
115      removeFromParent();
116    } else {
117      final opacity = 1 - radius / maxRadius;
118      _paint.color = _baseColor.withOpacity(opacity);
119      _paint.strokeWidth = _outerRadius - _innerRadius;
120    }
121  }

Standardization and Templates

For every section or package added to the documentation, naming conventions, directory structure, and standardized table of contents are important. Every section and package must have a table of contents or an entry in the parent markdown file to allow navigation from the left sidebar menu in logical or alphabetical order. Additionally, naming conventions should be followed for organization, such as:

  • bridge_packages/package_name/

  • documentation_section/


Avoid having spaces in the paths to the docs since that will keep you from building the project due to this bug.

Building documentation locally

Building the documentation site on your own computer is fairly simple. All you need is the following:

  1. A working Flutter installation, accessible from the command line.

  2. Melos command-line tool, as per the contributing guide.

  3. A Python environment, with python version 3.8+ or higher. Having a dedicated python virtual environment is recommended but not required.

  4. Install the remaining requirements using the command

    melos run doc-setup

Once these prerequisites are met, you can build the documentation by using the built-in Melos target:

melos doc-build

The melos doc-build command here renders the documentation site into HTML. This command needs to be re-run every time you make changes to any of the documents. Luckily, it is smart enough to only rebuild the documents that have changed since the previous run, so usually, a rebuild takes only a second or two.

If you want to automatically recompile the docs every time there is a change to one of the files you can use the the built-in Melos target below, which will also serve and open your default browser with the docs.

melos doc-serve

When using the melos doc-serve command, the melos doc-build is only needed when there are changes to the sphinx theme. This is because the serve command both automatically compiles the docs on changes and also hosts them locally. The docs are served at http://localhost:8000/ by default.

There are other make commands that you may find occasionally useful too:

  • melos doc-clean removes all cached generated files (in case the system gets stuck in a bad state).

  • melos doc-linkcheck to check whether there are any broken links in the documentation.

  • melos doc-kill removes any orphaned TCP threads running on port 8000.

The generated html files will be in the doc/_build/html directory, you can view them directly by opening the file doc/_build/html/index.html in your browser. The only drawback is that the browser won’t allow any dynamic content in a file opened from a local drive. The solution to this is to run melos doc-serve.

If you ever run the melos doc-clean command, the server will need to be restarted, because the clean command deletes the entire html directory.


Avoid having spaces in the paths to the docs since that will keep you from building the project due to this bug.