wp_get_typography_value_and_unit

wp_get_typography_value_and_unit: 这个函数返回一个数组，包含排版选项的值和用于指定该值的单位。它需要两个参数：排版选项名称和一个默认值，如果该选项没有被设置，则返回: 该函数从数据库中检索排版选项并返回一个包含该值和单位的数组。

检查一个字符串的单位和值，并返回一个由`’值’和`’单位’组成的数组，例如数组（’42’, ‘rem’）。

function wp_get_typography_value_and_unit( $raw_value, $options = array() ) {
	if ( ! is_string( $raw_value ) && ! is_int( $raw_value ) && ! is_float( $raw_value ) ) {
		_doing_it_wrong(
			__FUNCTION__,
			__( 'Raw size value must be a string, integer, or float.' ),
			'6.1.0'
		);
		return null;
	}

	if ( empty( $raw_value ) ) {
		return null;
	}

	// Converts numbers to pixel values by default.
	if ( is_numeric( $raw_value ) ) {
		$raw_value = $raw_value . 'px';
	}

	$defaults = array(
		'coerce_to'        => '',
		'root_size_value'  => 16,
		'acceptable_units' => array( 'rem', 'px', 'em' ),
	);

	$options = wp_parse_args( $options, $defaults );

	$acceptable_units_group = implode( '|', $options['acceptable_units'] );
	$pattern                = '/^(d*.?d+)(' . $acceptable_units_group . '){1,1}$/';

	preg_match( $pattern, $raw_value, $matches );

	// Bails out if not a number value and a px or rem unit.
	if ( ! isset( $matches[1] ) || ! isset( $matches[2] ) ) {
		return null;
	}

	$value = $matches[1];
	$unit  = $matches[2];

	/*
	 * Default browser font size. Later, possibly could inject some JS to
	 * compute this `getComputedStyle( document.querySelector( "html" ) ).fontSize`.
	 */
	if ( 'px' === $options['coerce_to'] && ( 'em' === $unit || 'rem' === $unit ) ) {
		$value = $value * $options['root_size_value'];
		$unit  = $options['coerce_to'];
	}

	if ( 'px' === $unit && ( 'em' === $options['coerce_to'] || 'rem' === $options['coerce_to'] ) ) {
		$value = $value / $options['root_size_value'];
		$unit  = $options['coerce_to'];
	}

	/*
	 * No calculation is required if swapping between em and rem yet,
	 * since we assume a root size value. Later we might like to differentiate between
	 * :root font size (rem) and parent element font size (em) relativity.
	 */
	if ( ( 'em' === $options['coerce_to'] || 'rem' === $options['coerce_to'] ) && ( 'em' === $unit || 'rem' === $unit ) ) {
		$unit = $options['coerce_to'];
	}

	return array(
		'value' => round( $value, 3 ),
		'unit'  => $unit,
	);
}