swf_core #

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.

Scope #

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

• Parser: shapes (with gradients and bitmap fills), lossless & JPEG bitmaps, static/dynamic texts, buttons, sprites, frame labels; CWS (zlib) decompression; Shift_JIS string decoding.
• ActionScript VM: SWF4-era bytecode with Flash Lite 1.x semantics — variables, arithmetic/string ops, tellTarget, gotoAndPlay, GetURL / FSCommand2 via host hooks.
• Player model (SwfStage): frame advancing with correct VM/timeline priority semantics, key dispatch (SwfKeyCode — Flash Lite CondKeyPress codes), tap dispatch, button focus navigation, and root-timeline label notifications.

Out of scope: ActionScript 2/3, video, sound, 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);
  print('${movie.frameCount} frames @ ${movie.frameRate} fps');

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

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

A structure-dump CLI is included: dart run swf_core:swfdump movie.swf.

License #

MIT