themes-wordpress/photos/inc/icon-functions.php

<?php
/**
 * SVG icons related functions and filters
 */

/**
 * Add SVG definitions to the footer.
 */
function photos_include_svg_icons() {
	// Define SVG sprite file.
	$svg_icons = get_parent_theme_file_path( '/icons/svg-icons.svg' );

	// If it exists, include it.
	if ( file_exists( $svg_icons ) ) {
		require_once( $svg_icons );
	}
}
add_action( 'wp_footer', 'photos_include_svg_icons', 9999 );

/**
 * Return SVG markup.
 *
 * @param array $args {
 *     Parameters needed to display an SVG.
 *
 *     @type string $icon  Required SVG icon filename.
 *     @type string $title Optional SVG title.
 *     @type string $desc  Optional SVG description.
 * }
 * @return string SVG markup.
 */
function photos_get_svg( $args = array() ) {
	$unique_id = null;
	// Make sure $args are an array.
	if ( empty( $args ) ) {
		return __( 'Please define default parameters in the form of an array.', 'photos' );
	}

	// Define an icon.
	if ( false === array_key_exists( 'icon', $args ) ) {
		return __( 'Please define an SVG icon filename.', 'photos' );
	}

	// Set defaults.
	$defaults = array(
		'icon'        => '',
		'title'       => '',
		'desc'        => '',
		'fallback'    => false,
	);

	// Parse args.
	$args = wp_parse_args( $args, $defaults );

	// Set aria hidden.
	$aria_hidden = ' aria-hidden="true"';

	// Set ARIA.
	$aria_labelledby = '';

	/*
	 * Photos doesn't use the SVG title or description attributes; non-decorative icons are described with .screen-reader-text.
	 *
	 * However, child themes can use the title and description to add information to non-decorative SVG icons to improve accessibility.
	 *
	 * Example 1 with title: <?php echo photos_get_svg( array( 'icon' => 'arrow-right', 'title' => __( 'This is the title', 'textdomain' ) ) ); ?>
	 *
	 * Example 2 with title and description: <?php echo photos_get_svg( array( 'icon' => 'arrow-right', 'title' => __( 'This is the title', 'textdomain' ), 'desc' => __( 'This is the description', 'textdomain' ) ) ); ?>
	 *
	 * See https://www.paciellogroup.com/blog/2013/12/using-aria-enhance-svg-accessibility/.
	 */
	if ( $args['title'] ) {
		$aria_hidden     = '';
		$unique_id       = uniqid();
		$aria_labelledby = ' aria-labelledby="title-' . $unique_id . '"';

		if ( $args['desc'] ) {
			$aria_labelledby = ' aria-labelledby="title-' . $unique_id . ' desc-' . $unique_id . '"';
		}
	}

	// Begin SVG markup.
	$svg = '<svg class="icon icon-' . esc_attr( $args['icon'] ) . '"' . $aria_hidden . $aria_labelledby . ' role="img">';

	// Display the title.
	if ( $args['title'] ) {
		$svg .= '<title id="title-' . $unique_id . '">' . esc_html( $args['title'] ) . '</title>';

		// Display the desc only if the title is already set.
		if ( $args['desc'] ) {
			$svg .= '<desc id="desc-' . $unique_id . '">' . esc_html( $args['desc'] ) . '</desc>';
		}
	}

	/*
	 * Display the icon.
	 *
	 * The whitespace around `<use>` is intentional - it is a work around to a keyboard navigation bug in Safari 10.
	 *
	 * See https://core.trac.wordpress.org/ticket/38387.
	 */
	$svg .= ' <use href="#icon-' . esc_html( $args['icon'] ) . '" xlink:href="#icon-' . esc_html( $args['icon'] ) . '"></use> ';

	// Add some markup to use as a fallback for browsers that do not support SVGs.
	if ( $args['fallback'] ) {
		$svg .= '<span class="svg-fallback icon-' . esc_attr( $args['icon'] ) . '"></span>';
	}

	$svg .= '</svg>';

	return $svg;
}

/**
 * Add dropdown icon if menu item has children.
 *
 * @param  string $title The menu item's title.
 * @param  object $item  The current menu item.
 * @param  array  $args  An array of wp_nav_menu() arguments.
 * @param  int    $depth Depth of menu item. Used for padding.
 * @return string $title The menu item's title with dropdown icon.
 */
function photos_dropdown_icon_to_menu_link( $title, $item, $args, $depth ) {
	if ( 'menu-1' === $args->theme_location ) {
		foreach ( $item->classes as $value ) {
			if ( 'menu-item-has-children' === $value || 'page_item_has_children' === $value ) {
				$title = $title . photos_get_svg( array( 'icon' => 'expand' ) );
			}
		}
	}

	return $title;
}
add_filter( 'nav_menu_item_title', 'photos_dropdown_icon_to_menu_link', 10, 4 );

/**
 * Add an icon above the post thumbnail image (when appropriate)
 */
function photos_post_icon() {

	$icon = '';

	if ( is_sticky() ) {
		$icon = 'pinned';
		$title = esc_html__( 'Featured', 'photos' );
	} elseif ( post_password_required() ) {
		$icon = 'lock';
		$title = esc_html__( 'Password Protected', 'photos' );
	}

	if ( empty( $icon ) ) return;

	$args = array();
	$args['icon'] = $icon;
	$args['title'] = $title;

	return photos_get_svg( $args );

}