changeSizingTheme method
Implementation
void changeSizingTheme(Object mode) {
if (sizingMode == mode) return;
sizingMode = mode;
_theme = _theme.copyWith(sizingTheme: _sizingThemes[mode]);
notifyListeners();
_delegate
..onSizingThemeChanged(_theme.sizingTheme, mode)
..onThemeChanged(_theme, colorMode, mode);
}