protected function get_default_settings()
{
return ['size_units' => ['px'], 'range' => ['px' => ['min' => 0, 'max' => 100, 'step' => 1], 'em' => ['min' => 0.1, 'max' => 10, 'step' => 0.1], 'rem' => ['min' => 0.1, 'max' => 10, 'step' => 0.1], '%' => ['min' => 0, 'max' => 100, 'step' => 1], 'deg' => ['min' => 0, 'max' => 360, 'step' => 1]]];
}