functions.php

<?php
/**
 * Functions and template tags for using site logos.
 *
 * @package Jetpack
 */

/**
 * Retrieve the site logo URL or ID (URL by default). Pass in the string 'id' for ID.
 *
 * @uses get_option()
 * @uses esc_url_raw()
 * @uses set_url_scheme()
 * @return mixed The URL or ID of our site logo, false if not set
 * @since 1.0
 */
function jetpack_get_site_logo( $show = 'url' ) {
	$logo = site_logo()->logo;

	// Return false if no logo is set
	if ( ! isset( $logo['id'] ) || 0 == $logo['id'] ) {
		return false;
	}

	// Return the ID if specified, otherwise return the URL by default
	if ( 'id' == $show ) {
		return $logo['id'];
	} else {
		return esc_url_raw( set_url_scheme( $logo['url'] ) );
	}
}

/**
 * Retrieve an array of the dimensions of the Site Logo.
 *
 * @uses Site_Logo::theme_size()
 * @uses get_option( 'thumbnail_size_w' )
 * @uses get_option( 'thumbnail_size_h' )
 * @uses global $_wp_additional_image_sizes;
 *
 * @since 3.6.0
 *
 * @return array $dimensions {
 *		An array of dimensions of the Site Logo.
 *
 * 		@type string $width Width of the logo in pixels.
 * 		@type string $height Height of the logo in pixels.
 * }
 */
function jetpack_get_site_logo_dimensions() {
	// Get the image size to use with the logo.
	$size = site_logo()->theme_size();

	// If the size is the default `thumbnail`, get its dimensions. Otherwise, get them from $_wp_additional_image_sizes
	if ( empty( $size ) ) {
		return false;
	} else if ( 'thumbnail' == $size ) {
		$dimensions  = array(
			'width'  => get_option( 'thumbnail_size_w' ),
			'height' => get_option( 'thumbnail_size_h' ),
		);
	} else {
		global $_wp_additional_image_sizes;

		if ( ! isset( $_wp_additional_image_sizes[ $size ] ) ) {
			return false;
		}

		$dimensions  = array(
			'width'  => $_wp_additional_image_sizes[ $size ][ 'width' ],
			'height' => $_wp_additional_image_sizes[ $size ][ 'height' ],
		);
	}

	return $dimensions;
}

/**
 * Determine if a site logo is assigned or not.
 *
 * @uses get_option
 * @return boolean True if there is an active logo, false otherwise
 */
function jetpack_has_site_logo() {
	return site_logo()->has_site_logo();
}

/**
 * Output an <img> tag of the site logo, at the size specified
 * in the theme's add_theme_support() declaration.
 *
 * @uses Site_Logo::logo
 * @uses Site_Logo::theme_size()
 * @uses jetpack_has_site_logo()
 * @uses jetpack_is_customize_preview()
 * @uses esc_url()
 * @uses home_url()
 * @uses esc_attr()
 * @uses wp_get_attachment_image()
 * @uses apply_filters()
 * @since 1.0
 */
function jetpack_the_site_logo() {
	$logo = site_logo()->logo;
	$logo_id = get_theme_mod( 'custom_logo' ); // Check for WP 4.5 Site Logo
	$logo_id = $logo_id ? $logo_id : $logo['id']; // Use WP Core logo if present, otherwise use Jetpack's.
	$size = site_logo()->theme_size();
	$html = '';

	// If no logo is set, but we're in the Customizer, leave a placeholder (needed for the live preview).
	if ( ! jetpack_has_site_logo() ) {
		if ( jetpack_is_customize_preview() ) {
			$html = sprintf( '<a href="%1$s" class="site-logo-link" style="display:none;"><img class="site-logo" data-size="%2$s" /></a>',
				esc_url( home_url( '/' ) ),
				esc_attr( $size )
			);
		}
	}

	// We have a logo. Logo is go.
	else {
		$html = sprintf( '<a href="%1$s" class="site-logo-link" rel="home" itemprop="url">%2$s</a>',
			esc_url( home_url( '/' ) ),
			wp_get_attachment_image(
				$logo_id,
				$size,
				false,
				array(
					'class'     => "site-logo attachment-$size",
					'data-size' => $size,
					'itemprop'  => "logo"
				)
			)
		);
	}

	/**
	 * Filter the Site Logo output.
	 *
	 * @module theme-tools
	 *
	 * @since 3.2.0
	 *
	 * @param string $html Site Logo HTML output.
	 * @param array $logo Array of Site Logo details.
	 * @param string $size Size specified in add_theme_support declaration, or 'thumbnail' default.
	 */
	echo apply_filters( 'jetpack_the_site_logo', $html, $logo, $size );
}

/**
 * Whether the site is being previewed in the Customizer.
 * Duplicate of core function until 4.0 is released.
 *
 * @global WP_Customize_Manager $wp_customize Customizer instance.
 * @return bool True if the site is being previewed in the Customizer, false otherwise.
 */
function jetpack_is_customize_preview() {
	global $wp_customize;

	return is_a( $wp_customize, 'WP_Customize_Manager' ) && $wp_customize->is_preview();
}

/**
 * Sanitize the string of classes used for header text.
 * Limit to A-Z,a-z,0-9,(space),(comma),_,-
 *
 * @return string Sanitized string of CSS classes.
 */
function jetpack_sanitize_header_text_classes( $classes ) {
	$classes = preg_replace( '/[^A-Za-z0-9\,\ ._-]/', '', $classes );

	return $classes;
}