swf_core

pub package CI license: MIT

A pure-Dart SWF4 / Flash Lite 1.x parser, player model, and ActionScript interpreter. No Flutter dependency — runs on the Dart VM, AOT, and Web.

swf_core is the runtime core behind the swf_player Flutter widget package. Use swf_core directly when you need headless parsing/execution (CLI tools, tests, servers); use swf_player when you want to render and interact with SWF content in a Flutter app.

日本語の説明は下にあります

Scope

Targets the SWF4 feature set as used by Flash Lite 1.x content (Japanese feature-phone era games and animations).

Parser

Area Supported
File formats FWS (uncompressed) and CWS (zlib-compressed)
Shapes DefineShape 1–3: solid / gradient / bitmap fills, line styles, quadratic Bézier edges
Bitmaps DefineBitsLossless 1–2 (zlib), DefineBitsJPEG3 (JPEG + zlib alpha channel)
Text DefineEditText (dynamic text with variable binding), DefineText + DefineFont2 (static glyph text)
Buttons DefineButton2 with ButtonCondAction (CondKeyPress, over/press transitions)
Timeline DefineSprite (nested timelines), PlaceObject2 / RemoveObject2, FrameLabel, SetBackgroundColor
Strings Shift_JIS decoding (the encoding used by Japanese feature-phone content)

ActionScript VM

SWF4-era bytecode with Flash Lite 1.x semantics: variables, arithmetic/string/comparison ops, branches, gotoFrame/gotoLabel, play/stop, tellTarget (slash and dot paths), GetProperty / SetProperty, RandomNumber, GetTime, and GetURL / FSCommand2 via host hooks (SwfHost). DefaultSwfHost answers the date/time FSCommand2 queries with real values.

Player model (SwfStage)

Frame advancing with correct VM/timeline priority semantics, key dispatch (SwfKeyCode — Flash Lite CondKeyPress codes), tap dispatch with hit-testing, button focus navigation (4-way key movement between buttons, as on real handsets), and root-timeline label notifications.

Out of scope

ActionScript 2/3, video, sound, morph shapes, clip actions, and SWF5+ tags.

Usage

import 'dart:io';
import 'package:swf_core/swf_core.dart';

void main() {
  final bytes = File('movie.swf').readAsBytesSync();
  final movie = SwfParser.parse(bytes); // FWS and CWS both accepted
  print('${movie.frameCount} frames @ ${movie.frameRate} fps');

  final stage = SwfStage(movie);
  stage.onRootLabel = (label) => print('reached label: $label');
  stage.advanceFrame();
  stage.dispatchKey(SwfKeyCode.enter);
  print(stage.root.getVariable('score'));
}

Host integration (traces, GetURL, FSCommand2, time, randomness) is injected via SwfHost; DefaultSwfHost provides sensible defaults and an optional log callback.

Building synthetic SWFs (package:swf_core/testing.dart)

The testing library ships a byte-level SWF builder and an SWF4 bytecode assembler, so you can write fully self-contained tests — or generate demo content — without any real SWF assets:

import 'package:swf_core/testing.dart';

final swfBytes = (SwfBuilder()
      ..defineShapeRect(1, widthPx: 40, heightPx: 40, fillRgb: 0xCC5544)
      ..placeObject2(depth: 1, characterId: 1, translateXPx: 100)
      ..frameLabel('start')
      ..doAction(Asm().pushString('score').pushFloat(0).op(0x1D).build())
      ..showFrame())
    .build();

CLI

A structure-dump tool is included:

dart run swf_core:swfdump movie.swf

Known limitations

  • Button rollout (OverUpToIdle) actions are not fired on focus-out (the parser does not retain that flag); content that resets state on rollout may keep the rollover state.
  • Tap hit-testing approximates the hit shape with its transformed bounding box.

日本語

ガラケー時代の Flash Lite 1.x（SWF4） コンテンツを扱うPure Dart ランタイムです。パーサ・ActionScriptインタープリタ・プレイヤーモデル （フレーム進行/キー/タップ/フォーカスナビゲーション）を含み、Flutter非依存 なのでCLI・サーバ・テストからも使えます。FlutterでのUI再生には swf_player を使ってください。 package:swf_core/testing.dart の SwfBuilder/Asm で合成SWFを生成でき、 著作物に依存しないテスト・デモが書けます。音声・動画・ActionScript 2/3は 対象外です。

License

MIT

Libraries

swf_core
Pure-Dart Flash Lite 1.x (SWF4) parser, player model, and ActionScript VM.
testing
テスト・デモ用の合成SWF生成ユーティリティ。