GC_Customize_Manager::_sanitize_background_setting()

	public function _sanitize_background_setting( $value, $setting ) {
		if ( 'background_repeat' === $setting->id ) {
			if ( ! in_array( $value, array( 'repeat-x', 'repeat-y', 'repeat', 'no-repeat' ), true ) ) {
				return new GC_Error( 'invalid_value', __( 'Invalid value for background repeat.' ) );
			}
		} elseif ( 'background_attachment' === $setting->id ) {
			if ( ! in_array( $value, array( 'fixed', 'scroll' ), true ) ) {
				return new GC_Error( 'invalid_value', __( 'Invalid value for background attachment.' ) );
			}
		} elseif ( 'background_position_x' === $setting->id ) {
			if ( ! in_array( $value, array( 'left', 'center', 'right' ), true ) ) {
				return new GC_Error( 'invalid_value', __( 'Invalid value for background position X.' ) );
			}
		} elseif ( 'background_position_y' === $setting->id ) {
			if ( ! in_array( $value, array( 'top', 'center', 'bottom' ), true ) ) {
				return new GC_Error( 'invalid_value', __( 'Invalid value for background position Y.' ) );
			}
		} elseif ( 'background_size' === $setting->id ) {
			if ( ! in_array( $value, array( 'auto', 'contain', 'cover' ), true ) ) {
				return new GC_Error( 'invalid_value', __( 'Invalid value for background size.' ) );
			}
		} elseif ( 'background_preset' === $setting->id ) {
			if ( ! in_array( $value, array( 'default', 'fill', 'fit', 'repeat', 'custom' ), true ) ) {
				return new GC_Error( 'invalid_value', __( 'Invalid value for background size.' ) );
			}
		} elseif ( 'background_image' === $setting->id || 'background_image_thumb' === $setting->id ) {
			$value = empty( $value ) ? '' : esc_url_raw( $value );
		} else {
			return new GC_Error( 'unrecognized_setting', __( 'Unrecognized background setting.' ) );
		}
		return $value;
	}