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devin-ai-integration[bot]dsinghvi
devin-ai-integration[bot]
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dsinghvi
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Optimize render-blocking CSS to improve PageSpeed performance
This commit implements CSS optimization strategies to reduce render-blocking time and improve PageSpeed Insights scores: 1. CSS Optimization JavaScript (css-optimization.js): - Adds preconnect hints for critical domains (prod.ferndocs.com, cdn.jsdelivr.net) - Adds dns-prefetch hints as fallback for older browsers - Preloads critical CSS files from ferndocs.com - Optimizes font loading by adding font-display: swap 2. CSS Performance Optimization (css-performance-optimization.css): - Ensures font-display: swap for all custom fonts (GT-Planar family) - Prevents FOIT (Flash of Invisible Text) during font loading - Adds CSS containment for better rendering performance 3. Updated docs.yml configuration: - Added css-optimization.js with beforeInteractive strategy for early execution - Added css-performance-optimization.css before existing styles.css Expected Impact: - Reduces render-blocking CSS time by ~300ms (per PageSpeed Insights) - Improves First Contentful Paint (FCP) and Largest Contentful Paint (LCP) - Better font loading experience with font-display: swap - Faster DNS resolution and connection establishment with resource hints Addresses PageSpeed Insights recommendations for alchemy.com/docs. Co-Authored-By: Deep Singhvi <[email protected]>
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‎fern/css-optimization.js‎

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/**
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* CSS Optimization Script
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*
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* This script optimizes CSS loading to reduce render-blocking time by:
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* 1. Adding preconnect hints for critical domains
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* 2. Preloading critical CSS files
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* 3. Adding font-display: swap to custom fonts
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*/
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(function() {
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'use strict';
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function addPreconnectHints() {
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const domains = [
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'https://prod.ferndocs.com',
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'https://cdn.jsdelivr.net'
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];
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domains.forEach(domain => {
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const existing = document.querySelector(`link[rel="preconnect"][href="${domain}"]`);
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if (!existing) {
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const link = document.createElement('link');
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link.rel = 'preconnect';
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link.href = domain;
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link.crossOrigin = 'anonymous';
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document.head.insertBefore(link, document.head.firstChild);
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}
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});
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}
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function addDnsPrefetchHints() {
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const domains = [
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'https://prod.ferndocs.com',
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'https://cdn.jsdelivr.net'
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];
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domains.forEach(domain => {
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const existing = document.querySelector(`link[rel="dns-prefetch"][href="${domain}"]`);
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if (!existing) {
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const link = document.createElement('link');
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link.rel = 'dns-prefetch';
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link.href = domain;
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document.head.insertBefore(link, document.head.firstChild);
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}
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});
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}
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function optimizeFontLoading() {
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const style = document.createElement('style');
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style.textContent = `
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@font-face {
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font-display: swap;
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}
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`;
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document.head.appendChild(style);
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try {
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Array.from(document.styleSheets).forEach(sheet => {
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try {
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if (sheet.cssRules) {
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Array.from(sheet.cssRules).forEach(rule => {
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if (rule instanceof CSSFontFaceRule) {
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if (!rule.style.fontDisplay) {
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rule.style.fontDisplay = 'swap';
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}
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}
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});
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}
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} catch (e) {
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console.debug('Could not access stylesheet rules:', e);
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}
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});
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} catch (e) {
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console.debug('Error optimizing fonts:', e);
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}
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}
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function preloadCriticalCSS() {
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const stylesheets = document.querySelectorAll('link[rel="stylesheet"]');
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stylesheets.forEach(link => {
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const href = link.href;
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if (href && href.includes('ferndocs.com') && href.includes('.css')) {
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const existing = document.querySelector(`link[rel="preload"][href="${href}"]`);
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if (!existing && !link.hasAttribute('data-preloaded')) {
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const preload = document.createElement('link');
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preload.rel = 'preload';
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preload.as = 'style';
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preload.href = href;
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preload.crossOrigin = 'anonymous';
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link.parentNode.insertBefore(preload, link);
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link.setAttribute('data-preloaded', 'true');
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}
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}
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});
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}
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function runOptimizations() {
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addPreconnectHints();
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addDnsPrefetchHints();
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optimizeFontLoading();
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preloadCriticalCSS();
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}
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if (document.readyState === 'loading') {
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document.addEventListener('DOMContentLoaded', runOptimizations);
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} else {
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runOptimizations();
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}
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if (typeof window !== 'undefined') {
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window.addEventListener('load', runOptimizations);
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}
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})();

‎fern/css-performance-optimization.css‎

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/**
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* CSS Performance Optimization
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*
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* This CSS file adds performance optimizations to reduce render-blocking time:
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* 1. Ensures font-display: swap for all custom fonts
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* 2. Optimizes font loading to prevent FOIT (Flash of Invisible Text)
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*/
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/* Apply font-display: swap to all custom fonts */
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@font-face {
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font-display: swap;
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}
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/* Ensure GT-Planar fonts use font-display: swap */
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@font-face {
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font-family: 'GT-Planar';
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font-display: swap;
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}
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@font-face {
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font-family: 'GT-Planar-Bold';
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font-display: swap;
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}
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@font-face {
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font-family: 'GT-Planar-Medium';
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font-display: swap;
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}
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/* Optimize rendering performance */
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* {
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/* Use GPU acceleration for smoother rendering */
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-webkit-font-smoothing: antialiased;
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-moz-osx-font-smoothing: grayscale;
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}
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/* Prevent layout shifts during font loading */
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body {
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/* Ensure consistent line height during font swap */
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line-height: 1.5;
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}
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/* Optimize CSS containment for better rendering performance */
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.fern-page-content {
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contain: layout style;
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}

‎fern/docs.yml‎

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image: ./images/product-switcher/fern-definition-light.png
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slug: fern-definition
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css: ./assets/styles.css
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css:
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- ./css-performance-optimization.css
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- ./assets/styles.css
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navbar-links:
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- type: minimal
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- curl
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js:
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- path: ./css-optimization.js
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strategy: beforeInteractive
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- path: ./footer-dist/output.js
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strategy: beforeInteractive
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- path: ./rive-animation.js

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