feat: add font preloading to reduce fout

Author: julioest

antora-ui/src/partials/head-fonts.hbs

@@ -0,0 +1,32 @@
+<link rel="preconnect" href="https://cppalliance.org" crossorigin>
+<link rel="preload" href="https://cppalliance.org/fonts/NotoSansDisplay.ttf" as="font" type="font/ttf" crossorigin />
+<link rel="preload" href="https://cppalliance.org/fonts/NotoSansDisplay-Italic.ttf" as="font" type="font/ttf" crossorigin />
+<link rel="preload" href="https://cppalliance.org/fonts/NotoSansMono.ttf" as="font" type="font/ttf" crossorigin />
+<script>
+(function() {
+  'use strict';
+  if (!('fonts' in document)) return;
+  
+  var fontUrls = [
+    { family: 'Noto Sans', url: 'https://cppalliance.org/fonts/NotoSansDisplay.ttf', style: 'normal' },
+    { family: 'Noto Sans', url: 'https://cppalliance.org/fonts/NotoSansDisplay-Italic.ttf', style: 'italic' },
+    { family: 'Noto Sans Mono', url: 'https://cppalliance.org/fonts/NotoSansMono.ttf', style: 'normal' }
+  ];
+  
+  var fontPromises = fontUrls.map(function(fontConfig) {
+    var fontFace = new FontFace(fontConfig.family, 'url(' + fontConfig.url + ')', {
+      style: fontConfig.style
+    });
+    return fontFace.load().then(function(loadedFont) {
+      document.fonts.add(loadedFont);
+      return loadedFont;
+    }).catch(function() {
+      // Silently fail - fonts will fallback to CSS loading
+    });
+  });
+  
+  Promise.all(fontPromises).catch(function() {
+    // Silently fail - fonts will fallback to CSS loading
+  });
+})();
+</script>

antora-ui/src/partials/head.hbs

@@ -1,6 +1,7 @@
 {{> head-prelude}}
 {{> head-title}}
 {{> head-info}}
+{{> head-fonts}}
 {{> head-styles}}
 {{> head-scripts}}
 {{> head-icons}}