fix(favicon): dynamic favicon switching based on color scheme in js (#735)

* fix(favicon): dynamic favicon switching based on color scheme in js

* refactor(favicon): simplify favicon logic and ensure dynamic switching based on color scheme

* docs(favicon): enhance favicon setup instructions with dark mode support and adaptive SVG guidance

assets/js/favicon.js

@@ -0,0 +1,22 @@
+// {{ $faviconDarkExists := fileExists (path.Join "static" "favicon-dark.svg") }}
+(function () {
+  const faviconEl = document.getElementById("favicon-svg");
+  const faviconDarkExists = "{{ $faviconDarkExists }}" === "true";
+
+  if (faviconEl && faviconDarkExists) {
+    const lightFavicon = '{{ "favicon.svg" | relURL }}';
+    const darkFavicon = '{{ "favicon-dark.svg" | relURL }}';
+
+    const darkModeQuery = window.matchMedia("(prefers-color-scheme: dark)");
+
+    function updateFavicon(e) {
+      faviconEl.href = e.matches ? darkFavicon : lightFavicon;
+    }
+
+    // Set favicon on load
+    updateFavicon(darkModeQuery);
+
+    // Listen for system preference changes
+    darkModeQuery.addEventListener("change", updateFavicon);
+  }
+})();

exampleSite/content/docs/guide/configuration.md

@@ -188,10 +188,26 @@ To customize the [favicon](https://en.wikipedia.org/wiki/Favicon) for your site,
   {{< /filetree/folder >}}
 {{< /filetree/container >}}
 
-Include `favicon.ico`, `favicon.svg` and `favicon-dark.svg` files in your project to ensure your site's favicons display correctly.
+#### Basic Setup
 
-While `favicon.ico` is generally for older browsers, `favicon.svg` and `favicon-dark.svg` are supported by modern browsers.
-Use tools like [favicon.io](https://favicon.io/) or [favycon](https://github.com/ruisaraiva19/favycon) to generate such icons.
+At minimum, include `favicon.svg` in your `static` folder. This will be used as the default favicon for your site.
+
+You can create an adaptive SVG favicon that responds to system theme preferences by using CSS media queries within the SVG itself, following the approach described in [Building an Adaptive Favicon](https://web.dev/articles/building/an-adaptive-favicon).
+
+#### Dark Mode Support
+
+For enhanced dark mode support, add `favicon-dark.svg` to your `static` folder alongside `favicon.svg`. When both files are present, Hextra will automatically:
+
+- Use `favicon.svg` for light mode or when no theme preference is detected
+- Switch to `favicon-dark.svg` when the user's system is set to dark mode
+- Respect the system's `prefers-color-scheme` setting for automatic switching
+
+The dark mode favicon switching works across all modern browsers, including Firefox, and provides a seamless experience that matches your site's theme.
+
+#### Additional Formats
+
+While `favicon.ico` is generally for older browsers, modern browsers support SVG favicons which are preferred for their scalability and small file size.
+Use tools like [favicon.io](https://favicon.io/) or [favycon](https://github.com/ruisaraiva19/favycon) to generate additional favicon formats if needed.
 
 ### Theme Configuration
 

layouts/_partials/favicons.html

@@ -1,6 +1,5 @@
 <link rel="icon shortcut" href="{{ "favicon.ico" | relURL }}" sizes="32x32" />
-<link rel="icon" href="{{ "favicon.svg" | relURL }}" type="image/svg+xml" />
-<link rel="icon" href="{{ "favicon-dark.svg" | relURL }}" type="image/svg+xml" media="(prefers-color-scheme: dark)" />
+<link rel="icon" href="{{ "favicon.svg" | relURL }}" type="image/svg+xml" id="favicon-svg" />
 <link rel="icon" href="{{ "favicon-16x16.png" | relURL }}" type="image/png" sizes="16x16" />
 <link rel="icon" href="{{ "favicon-32x32.png" | relURL }}" type="image/png" sizes="32x32" />
 <link rel="apple-touch-icon" href="{{ "apple-touch-icon.png" | relURL }}" sizes="180x180" />

layouts/_partials/scripts/core.html

@@ -7,8 +7,9 @@
 {{- $jsFileTree := resources.Get "js/filetree.js" -}}
 {{- $jsSidebar := resources.Get "js/sidebar.js" -}}
 {{- $jsBackToTop := resources.Get "js/back-to-top.js" -}}
+{{- $jsFavicon := resources.Get "js/favicon.js" | resources.ExecuteAsTemplate "favicon.js" . -}}
 
-{{- $scripts := slice $jsTheme $jsMenu $jsCodeCopy $jsTabs $jsLang $jsNavMenu $jsFileTree $jsSidebar $jsBackToTop | resources.Concat "js/main.js" -}}
+{{- $scripts := slice $jsTheme $jsMenu $jsCodeCopy $jsTabs $jsLang $jsNavMenu $jsFileTree $jsSidebar $jsBackToTop $jsFavicon | resources.Concat "js/main.js" -}}
 {{- if hugo.IsProduction -}}
   {{- $scripts = $scripts | minify | fingerprint -}}
 {{- end -}}