build method

Implementation

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

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

    _elapsed += amount;

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

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

      if (_elapsed < duration) return;
      _elapsed -= duration;
      final next = _frame + 1;

      if (next < _sprite.frames(_row)) {
        _frame = next;
        _source = null;
        onFrame.emit(next);
      } else if (loops) {
        _frame = 0;
        _source = null;
        onFrame.emit(0);
        onLoop.emit();
      } else {
        _elapsed = 0;
        _finished = true;
        onFinish.emit();

        if (cleanup) {
          detach();
        }

        return;
      }
    }
  });

  void painter(Canvas canvas, Paint paint) {
    canvas.drawImageRect(
      _sprite.image(_row),
      _source ??= _sprite.rect(_row, _frame),
      _destination ??= .fromLTWH(0, 0, width, height),
      paint,
    );
  }

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

  debugDraw((canvas) {
    canvas.drawRect(.fromLTWH(0, 0, width, height), DEBUG_TRANSFORM_PAINT);
  });
}