getModifierSide method Null safety

  1. @override
KeyboardSide? getModifierSide(
  1. ModifierKey key
)
override

Returns a KeyboardSide enum value that describes which side or sides of the given keyboard modifier key were pressed at the time of this event.

If the modifier key wasn't pressed at the time of this event, returns null. If the given key only appears in one place on the keyboard, returns KeyboardSide.all if pressed. If the given platform does not specify the side, return KeyboardSide.any.

Implementation

@override
KeyboardSide? getModifierSide(ModifierKey key) {
  KeyboardSide? findSide(int leftMask, int rightMask, int anyMask) {
    final int combinedMask = leftMask | rightMask;
    final int combined = modifiers & combinedMask;
    if (combined == leftMask) {
      return KeyboardSide.left;
    } else if (combined == rightMask) {
      return KeyboardSide.right;
    } else if (combined == combinedMask || modifiers & (combinedMask | anyMask) == anyMask) {
      // Handles the case where Windows supplies just the "either" modifier
      // flag, but not the left/right flag. (e.g. modifierShift but not
      // modifierLeftShift).
      return KeyboardSide.all;
    }
    return null;
  }

  switch (key) {
    case ModifierKey.controlModifier:
      return findSide(modifierLeftControl, modifierRightControl, modifierControl);
    case ModifierKey.shiftModifier:
      return findSide(modifierLeftShift, modifierRightShift, modifierShift);
    case ModifierKey.altModifier:
      return findSide(modifierLeftAlt, modifierRightAlt, modifierAlt);
    case ModifierKey.metaModifier:
      return findSide(modifierLeftMeta, modifierRightMeta, 0);
    case ModifierKey.capsLockModifier:
    case ModifierKey.numLockModifier:
    case ModifierKey.scrollLockModifier:
    case ModifierKey.functionModifier:
    case ModifierKey.symbolModifier:
      return KeyboardSide.all;
  }
}