wp_get_global_stylesheet

wp_get_global_stylesheet: 这个函数返回wp-admin.css文件的内容，该文件用于设计WordPress管理界面的样式。

返回合并核心、主题和用户数据后的样式表。

function wp_get_global_stylesheet( $types = array() ) {
	// Return cached value if it can be used and exists.
	// It's cached by theme to make sure that theme switching clears the cache.
	$can_use_cached = (
		( empty( $types ) ) &&
		( ! defined( 'WP_DEBUG' ) || ! WP_DEBUG ) &&
		( ! defined( 'SCRIPT_DEBUG' ) || ! SCRIPT_DEBUG ) &&
		( ! defined( 'REST_REQUEST' ) || ! REST_REQUEST ) &&
		! is_admin()
	);
	$transient_name = 'global_styles_' . get_stylesheet();
	if ( $can_use_cached ) {
		$cached = get_transient( $transient_name );
		if ( $cached ) {
			return $cached;
		}
	}

	$tree = WP_Theme_JSON_Resolver::get_merged_data();

	$supports_theme_json = WP_Theme_JSON_Resolver::theme_has_support();
	if ( empty( $types ) && ! $supports_theme_json ) {
		$types = array( 'variables', 'presets', 'base-layout-styles' );
	} elseif ( empty( $types ) ) {
		$types = array( 'variables', 'styles', 'presets' );
	}

	/*
	 * If variables are part of the stylesheet, then add them.
	 * This is so themes without a theme.json still work as before 5.9:
	 * they can override the default presets.
	 * See https://core.trac.wordpress.org/ticket/54782
	 */
	$styles_variables = '';
	if ( in_array( 'variables', $types, true ) ) {
		/*
		 * Only use the default, theme, and custom origins. Why?
		 * Because styles for `blocks` origin are added at a later phase
		 * (i.e. in the render cycle). Here, only the ones in use are rendered.
		 * @see wp_add_global_styles_for_blocks
		 */
		$origins          = array( 'default', 'theme', 'custom' );
		$styles_variables = $tree->get_stylesheet( array( 'variables' ), $origins );
		$types            = array_diff( $types, array( 'variables' ) );
	}

	/*
	 * For the remaining types (presets, styles), we do consider origins:
	 *
	 * - themes without theme.json: only the classes for the presets defined by core
	 * - themes with theme.json: the presets and styles classes, both from core and the theme
	 */
	$styles_rest = '';
	if ( ! empty( $types ) ) {
		/*
		 * Only use the default, theme, and custom origins. Why?
		 * Because styles for `blocks` origin are added at a later phase
		 * (i.e. in the render cycle). Here, only the ones in use are rendered.
		 * @see wp_add_global_styles_for_blocks
		 */
		$origins = array( 'default', 'theme', 'custom' );
		if ( ! $supports_theme_json ) {
			$origins = array( 'default' );
		}
		$styles_rest = $tree->get_stylesheet( $types, $origins );
	}

	$stylesheet = $styles_variables . $styles_rest;

	if ( $can_use_cached ) {
		// Cache for a minute.
		// This cache doesn't need to be any longer, we only want to avoid spikes on high-traffic sites.
		set_transient( $transient_name, $stylesheet, MINUTE_IN_SECONDS );
	}

	return $stylesheet;
}