Prefetch the sidebar logos

Author: pradyunsg

src/furo/theme/furo/base.html

@@ -31,6 +31,16 @@
         {%- if pageurl %}
         <link rel="canonical" href="{{ pageurl|e }}" />
         {%- endif %}
+
+        {%- block logo_prefetch_links %}
+        {%- if logo_url %}
+        <link rel="prefetch" href="{{ logo_url }}" as="image" />
+        {%- endif %}
+        {%- if theme_light_logo and theme_dark_logo %}
+        <link rel="prefetch" href="{{ pathto('_static/' + theme_light_logo, 1) }}" as="image" />
+        <link rel="prefetch" href="{{ pathto('_static/' + theme_dark_logo, 1) }}" as="image" />
+        {%- endif %}
+        {%- endblock logo_prefetch_links %}
     {%- endblock linktags %}
 
     {# Favicon #}

src/furo/theme/furo/sidebar/brand.html

@@ -12,7 +12,8 @@
 
 -#}
 <a class="sidebar-brand{% if logo %} centered{% endif %}" href="{{ pathto(master_doc) }}">
-  {% block brand_content %}
+  {%- block brand_content %}
+  {#- Remember to update the prefetch logic in `block logo_prefetch_links` in base.html #}
   {%- if logo_url %}
   <div class="sidebar-logo-container">
     <img class="sidebar-logo" src="{{ logo_url }}" alt="Logo"/>