onKey method Null safety

Implementation

KeyEventResult onKey(RawKeyEvent e) {
  if (e is! RawKeyDownEvent) {
    if (e is RawKeyUpEvent && e.physicalKey == _physicalKeyThatIsDown) {
      releasePressedButton();
      _physicalKeyThatIsDown = null;
    }
    return KeyEventResult.ignored;
  }
  final now = DateTime.now();
  if (e.physicalKey == _physicalKeyThatIsDown &&
      now.difference(lastKeyDown).inMilliseconds < 2000) {
    // Effectively, disable autorepeat.
    lastKeyDown = now;
    return KeyEventResult.handled;
  }
  final Characters ch;
  if (e.physicalKey == PhysicalKeyboardKey.enter ||
      e.physicalKey == PhysicalKeyboardKey.numpadEnter) {
    // Bizarrely, on the web we get 'E' as the character in this case!
    // https://github.com/flutter/flutter/issues/82065
    ch = Characters('\n');
  } else if (e.physicalKey == PhysicalKeyboardKey.delete ||
      e.physicalKey == PhysicalKeyboardKey.backspace) {
    ch = Characters('\u0008');
  } else if (_ignored.contains(e.physicalKey)) {
    // Other keys give weird results on the web, alas.  Like, control
    // gives "C".  I didn't file a bug, but I may post a flaming screed
    // to alt.javascript.die.die.die
    return KeyEventResult.ignored;
  } else {
    String? sch = e.character;
    if (sch == null) {
      return KeyEventResult.ignored;
    }
    if (e.isControlPressed && (sch == 'f' || sch == 'F')) {
      // Yes, JavaScript really does suck.  In case you were wondering.
      ch = Characters('\u0006');
    } else if (e.isControlPressed && (sch == 'g' || sch == 'G')) {
      ch = Characters('\u0007');
    } else {
      ch = Characters(sch).toUpperCase();
    }
    if (ch.isEmpty) {
      return KeyEventResult.ignored;
    }
  }
  final CalculatorButtonState? b = button[ch.first];
  if (b != null) {
    releasePressedButton(); // Just in case, probably does nothing
    if (e.character == '<' || e.character == '>') {
      final gShift = button['G'];
      assert(gShift != null);
      if (gShift != null) {
        // Shut up analyzer
        gShift.keyPressed();
        _extraShiftThatIsDown = gShift;
      }
    }
    b.keyPressed();
    _buttonThatIsDown = b;
    _physicalKeyThatIsDown = e.physicalKey;
    lastKeyDown = now;
    return KeyEventResult.handled;
  } else if (e.character == '?') {
    controller.model.settings.showAccelerators.value =
        !controller.model.settings.showAccelerators.value;
    _physicalKeyThatIsDown = e.physicalKey;
    lastKeyDown = now;
    return KeyEventResult.handled;
  }
  return KeyEventResult.ignored;
}