build method

Implementation

@override
void build() {
  super.build();

  tick((dt) {
    final state = _current;
    if (state.isFinished) return;
    final amount = dt * speed;
    if (amount <= 0 || !amount.isFinite) return;

    state._elapsed += amount;

    // Every pass re-reads the state, so a handler calling play() redirects
    // this loop instead of racing it.
    while (true) {
      final duration = state._entry.duration(state.frame);

      if (duration <= 0 || !duration.isFinite) {
        state._elapsed = 0;
        return;
      }

      if (state._elapsed < duration) return;
      state._elapsed -= duration;
      final next = state.frame + 1;

      if (next < state._entry.frames) {
        state._seek(next);
      } else if (state.loops) {
        state._seek(0);
        onLoop.emit();
      } else {
        state._elapsed = 0;
        state._finished = true;
        onFinish.emit();

        if (cleanup) {
          detach();
        }

        return;
      }
    }
  });

  void painter(Canvas canvas, Paint paint) {
    final state = _current;

    canvas.drawImageRect(
      state._entry.image,
      state._source ??= state._entry.rect(state.frame),
      state._destination ??= .fromLTWH(0, 0, width, height),
      paint,
    );
  }

  draw((canvas) {
    palette.draw(canvas, painter);
  });

  Ignis.cache.onChanged(() {
    _sprite = _sprite.reload();

    // Follow the entry by name. A dropped entry falls back to the first; a
    // shorter one starts over.
    final entry = _sprite.resolve(_current.key);

    if (entry == null) {
      _current._select(_sprite.entries.first, 0);
      return;
    }

    final frame = _current.frame;
    _current._select(entry, frame < entry.frames ? frame : 0);
  });
}