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<?php |
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/** |
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* Resource Hints module — LCP-image preload + preconnect. |
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* |
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* NB: distinct from the Preloader module (crawler / cache warming). This one |
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* rewrites a page's HTML with browser resource hints (preload, preconnect); |
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* the Preloader warms the server-side page cache. Different layer, different |
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* metric — this moves LCP/FCP, the crawler moves TTFB. See docs/notes. |
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* |
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* The single biggest lever on Largest Contentful Paint is telling the |
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* browser to fetch the hero image immediately, in the <head>, instead of |
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* waiting for CSS + layout to discover it (and past any loading="lazy" the |
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* theme set). WP Rocket's LCP edge in the GTmetrix comparison came entirely |
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* from this. Page-builder heroes (Elementor etc.) are rendered outside |
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* the_content, so the Lazy module's eager-first-N never sees them — this |
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* module works on the full page buffer instead. |
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* |
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* Two Free behaviors (FEATURES.md rows 115 basic preload, 125/356 preconnect): |
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* - LCP image preload: <link rel="preload" as="image" fetchpriority="high"> |
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* for the first above-the-fold <img>, plus fetchpriority="high" on the tag. |
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* - Preconnect: <link rel="preconnect"> for detected font hosts + a user list. |
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* |
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* Runs on the cache-write path via the xspeed_cache_final_html filter so the |
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* hints are baked into the cached HTML and replayed on every HIT (a wp_head |
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* hook would never fire on a HIT — the drop-in short-circuits before PHP). |
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* When page caching is OFF it buffers the page itself at template_redirect. |
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* |
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* LCP detection sees through JS-lazy heroes (real URL in data-src) and skips |
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* logos/icons via a size + marker gate, so the preload targets the actual |
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* hero rather than the first plain <img> in the DOM. Format-negotiating layers |
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* (e.g. Pro's Images module, which wraps the LCP <img> in a <picture> with a |
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* WebP/AVIF <source>) coordinate through the `xspeed_lcp_preload_url` / |
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* `xspeed_lcp_preload_srcset` / `xspeed_lcp_preload_type` filters so the |
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* high-priority preload points at the format actually served. (FBS-83553) |
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* |
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* @package XSpeed |
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*/ |
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|
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declare(strict_types=1); |
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|
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namespace XSpeed\Modules\ResourceHints; |
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|
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defined( 'ABSPATH' ) || exit; |
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|
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use XSpeed\Module; |
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use XSpeed\Resource_Hints_Processor; |
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use XSpeed\Settings_Manager; |
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|
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final class ResourceHintsModule extends Module { |
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|
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public const SLUG = 'resource-hints'; |
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public const TIER = self::TIER_FREE; |
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public const VERSION = '1.0.0'; |
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|
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/** Guards the cache-off buffer so it processes exactly once per request. */ |
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private static $buffering = false; |
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|
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public function ui_metadata(): array { |
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return array( |
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'label' => 'Resource Hints', |
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'tab_label' => 'Hints', // its own tab on the Resource Hints page |
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'icon' => 'Zap', |
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'description' => 'Preload the LCP hero image and preconnect to font hosts so the largest element paints sooner.', |
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// Host page: Hints (this module) + a Speculation Rules section |
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// (SmartPredict, Pro). SmartPredict prefetches the next page in |
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// the visitor's browser — same family as preload/preconnect, so |
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// it belongs here, not under AI (FBS-83633). |
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'custom_panel' => 'ResourceHintsPanel', |
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); |
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} |
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|
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public function settings_schema(): array { |
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return array( |
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'enabled' => array( |
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'type' => 'bool', |
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'default' => true, |
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'label' => 'Enable Resource Hints', |
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'description' => 'Master switch for the LCP-image preload + preconnect resource hints. On by default — these are safe, no-config optimizations that help every theme.', |
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), |
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'lcp_preload' => array( |
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'type' => 'bool', |
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'default' => true, |
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'label' => 'Preload LCP Image', |
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'description' => 'Detect the largest above-the-fold image and emit a <link rel="preload" as="image" fetchpriority="high"> in the head, plus fetchpriority="high" on the image. This is the highest-impact fix for Largest Contentful Paint — it beats any lazy-load the theme applied.', |
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), |
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'lcp_image_count' => array( |
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'type' => 'int', |
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'default' => 1, |
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'min' => 0, |
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'max' => 3, |
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'label' => 'Images to Preload', |
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'description' => 'How many of the first images on the page to preload. 1 is right for most sites (the single hero). Raise it only if the fold shows a small gallery.', |
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), |
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'lcp_exclusions' => array( |
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'type' => 'list', |
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'default' => array(), |
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'item_type' => 'string', |
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'label' => 'Exclude From Preload', |
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'description' => 'Substring patterns (filename or class) that, if found in an <img>, exempt it from being treated as the LCP image. Useful for tracking pixels, spacers, or a decorative first image that is not the hero.', |
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), |
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'preconnect' => array( |
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'type' => 'bool', |
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'default' => true, |
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'label' => 'Preconnect to Font Hosts', |
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'description' => 'When Google Fonts are detected, emit <link rel="preconnect"> to fonts.googleapis.com and fonts.gstatic.com so the DNS + TLS handshake happens ahead of the font request instead of on the critical path.', |
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), |
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'preconnect_hosts' => array( |
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'type' => 'list', |
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'default' => array(), |
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'item_type' => 'url', |
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'label' => 'Extra Preconnect Hosts', |
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'description' => 'One origin per line (e.g. https://cdn.example.com) to preconnect in addition to the auto-detected font hosts. Use for a CDN or third-party origin that serves above-the-fold assets.', |
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), |
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); |
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} |
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|
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public function boot(): void { |
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// Frontend page renders only. Admin / feed / cron / AJAX / REST never |
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// produce an HTML document we should rewrite. |
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if ( is_admin() |
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|| ( defined( 'DOING_AJAX' ) && DOING_AJAX ) |
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|| ( defined( 'DOING_CRON' ) && DOING_CRON ) |
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|| ( defined( 'REST_REQUEST' ) && REST_REQUEST ) |
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) { |
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return; |
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} |
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|
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$opts = $this->get_settings(); |
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if ( empty( $opts['enabled'] ) ) { |
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return; |
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} |
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|
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$any = ! empty( $opts['lcp_preload'] ) || ! empty( $opts['preconnect'] ) || ! empty( $opts['preconnect_hosts'] ); |
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if ( ! $any ) { |
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return; |
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} |
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|
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// Cache-write path: transform the HTML just before it is minified and |
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// written to the cache file, so hints are baked in and survive HITs. |
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add_filter( |
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'xspeed_cache_final_html', |
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function ( $html ) { |
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return Resource_Hints_Processor::process( (string) $html, $this->processor_opts() ); |
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}, |
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10, |
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1 |
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); |
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|
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// Cache-off path: the cache filter above never fires, so buffer the |
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// page ourselves. Guarded so we don't double-buffer when the cache |
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// engine is also running (its filter handles that case). |
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if ( ! $this->cache_enabled() ) { |
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add_action( |
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'template_redirect', |
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function () { |
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if ( self::$buffering ) { |
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return; |
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} |
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self::$buffering = true; |
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ob_start( |
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function ( $buffer ) { |
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if ( strlen( (string) $buffer ) < 255 ) { |
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return $buffer; |
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} |
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return Resource_Hints_Processor::process( (string) $buffer, $this->processor_opts() ); |
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} |
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); |
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}, |
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9 |
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); |
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} |
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} |
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|
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/** |
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* Is the page cache turned on? When it is, Cache::finalize_buffer runs and |
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* our xspeed_cache_final_html filter fires — so we must NOT also ob_start. |
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*/ |
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private function cache_enabled(): bool { |
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$legacy = Settings_Manager::get( 'legacy' ); |
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if ( is_array( $legacy ) && ! empty( $legacy['cache_enabled'] ) ) { |
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return true; |
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} |
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$opts = get_option( 'xspeed_options' ); |
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return is_array( $opts ) && ! empty( $opts['cache_enabled'] ); |
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} |
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|
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/** |
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* Settings passed to the full-page processor: this module's own settings, |
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* plus the Lazy module's `excluded_images` list. The processor runs over the |
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* WHOLE page (via xspeed_cache_final_html), so it can reach a theme/builder |
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* hero rendered OUTSIDE the_content — which the Lazy module's the_content- |
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* scoped filters can't. Surfacing the exclusions here lets the processor |
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* strip core's loading="lazy" + set fetchpriority=high on those heroes so an |
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* excluded above-the-fold image actually loads eagerly no matter where the |
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* theme printed it. (FBS-83553 H2) |
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*/ |
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private function processor_opts(): array { |
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$opts = $this->get_settings(); |
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if ( class_exists( '\XSpeed\Settings_Manager' ) ) { |
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$lazy = Settings_Manager::get( 'lazy' ); |
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if ( is_array( $lazy ) && ! empty( $lazy['lazy_images'] ) && ! empty( $lazy['excluded_images'] ) && is_array( $lazy['excluded_images'] ) ) { |
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$opts['eager_excluded_images'] = array_values( array_filter( array_map( 'strval', $lazy['excluded_images'] ) ) ); |
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} |
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} |
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return $opts; |
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} |
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|
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public function cli_commands(): array { |
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return array( |
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array( |
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'name' => 'xspeed resource-hints', |
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'callback' => array( $this, 'cli_handler' ), |
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'shortdesc' => 'Show LCP-preload / preconnect resource-hint settings.', |
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'synopsis' => array(), |
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), |
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); |
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} |
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|
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public function cli_handler( array $args, array $assoc ): void { |
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$opts = $this->get_settings(); |
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\WP_CLI::log( sprintf( '%-20s %s', 'enabled', ! empty( $opts['enabled'] ) ? 'on' : 'off' ) ); |
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\WP_CLI::log( sprintf( '%-20s %s', 'lcp_preload', ! empty( $opts['lcp_preload'] ) ? 'on' : 'off' ) ); |
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\WP_CLI::log( sprintf( '%-20s %d', 'lcp_image_count', (int) ( $opts['lcp_image_count'] ?? 1 ) ) ); |
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\WP_CLI::log( sprintf( '%-20s %d pattern(s)', 'lcp_exclusions', count( (array) ( $opts['lcp_exclusions'] ?? array() ) ) ) ); |
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\WP_CLI::log( sprintf( '%-20s %s', 'preconnect', ! empty( $opts['preconnect'] ) ? 'on' : 'off' ) ); |
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\WP_CLI::log( sprintf( '%-20s %d host(s)', 'preconnect_hosts', count( (array) ( $opts['preconnect_hosts'] ?? array() ) ) ) ); |
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} |
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} |
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|
