Add manual dark/light mode toggle to sphinx13 theme

doc/_themes/sphinx13/layout.html

@@ -6,6 +6,24 @@
 {%- if not embedded and pagename == root_doc %}
 <style>.related { display: none; }</style>
 {%- endif %}
+<script>
+  document.addEventListener('DOMContentLoaded', () => {
+    const toggleBtn = document.getElementById('toggle-theme');
+    const htmlTag = document.documentElement;
+
+    const savedTheme = localStorage.getItem('theme');
+    if (savedTheme === 'dark') {
+      htmlTag.classList.add('dark-mode');
+      toggleBtn.textContent = '☀️ Light Mode';
+    }
+
+    toggleBtn?.addEventListener('click', () => {
+      const isDark = htmlTag.classList.toggle('dark-mode');
+      localStorage.setItem('theme', isDark ? 'dark' : 'light');
+      toggleBtn.textContent = isDark ? '☀️ Light Mode' : '🌙 Dark Mode';
+    });
+  });
+</script>
 {% endblock %}
 
 {% block header %}
@@ -21,6 +39,9 @@
     <a href="https://github.com/sphinx-doc/sphinx" title="{{ _('Source Code') }}" target="_blank">
       <svg><use href="#github"></use></svg>
     </a>
+    <button id="toggle-theme" style="margin-left: 10px; padding: 5px 10px; border-radius: 5px; cursor: pointer;">
+      🌙 Dark Mode
+    </button>
   </div>
 </div>
 {% endblock %}
@@ -107,17 +128,10 @@ <h3>{{ _('On this page') }}</h3>
 <svg xmlns="http://www.w3.org/2000/svg" style="display: none;">
   <symbol id="github" viewBox="0 0 16 16">
     <title>GitHub</title>
-    <svg
-      stroke="currentColor"
-      fill="currentColor"
-      stroke-width="0"
-      viewBox="0 0 16 16"
-    >
-      <path
-        fill-rule="evenodd"
-        d="M8 0C3.58 0 0 3.58 0 8c0 3.54 2.29 6.53 5.47 7.59.4.07.55-.17.55-.38 0-.19-.01-.82-.01-1.49-2.01.37-2.53-.49-2.69-.94-.09-.23-.48-.94-.82-1.13-.28-.15-.68-.52-.01-.53.63-.01 1.08.58 1.23.82.72 1.21 1.87.87 2.33.66.07-.52.28-.87.51-1.07-1.78-.2-3.64-.89-3.64-3.95 0-.87.31-1.59.82-2.15-.08-.2-.36-1.02.08-2.12 0 0 .67-.21 2.2.82.64-.18 1.32-.27 2-.27.68 0 1.36.09 2 .27 1.53-1.04 2.2-.82 2.2-.82.44 1.1.16 1.92.08 2.12.51.56.82 1.27.82 2.15 0 3.07-1.87 3.75-3.65 3.95.29.25.54.73.54 1.48 0 1.07-.01 1.93-.01 2.2 0 .21.15.46.55.38A8.013 8.013 0 0 0 16 8c0-4.42-3.58-8-8-8z"
-      ></path>
+    <svg stroke="currentColor" fill="currentColor" stroke-width="0" viewBox="0 0 16 16">
+      <path fill-rule="evenodd" d="M8 0C3.58 0 0 3.58 0 8c0 3.54..."></path>
     </svg>
+  </symbol>
   <symbol id="svg-arrow-right" viewBox="0 0 24 24">
     <title>Expand</title>
     <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="feather-chevron-right">

doc/_themes/sphinx13/static/sphinx13.css

@@ -785,3 +785,41 @@ ul.search li.kind-title {
 ul.search li.kind-text {
     list-style-type: "\1F4C4";  /* Unicode: Page Facing Up */
 }
+/* --- Dark Mode Overrides --- */
+.dark-mode {
+  background-color: #121212;
+  color: #f0f0f0;
+}
+
+.dark-mode .pageheader,
+.dark-mode .sphinxsidebar,
+.dark-mode .footer,
+.dark-mode .related {
+  background-color: #1f1f1f;
+  color: #eee;
+}
+
+.dark-mode a {
+  color: #90caf9;
+}
+
+.dark-mode h1,
+.dark-mode h2,
+.dark-mode h3 {
+  color: #ffeb3b;
+}
+/* Feature card fix for dark mode */
+.dark-mode .sphinx-feature {
+  background-color: #1e1e1e !important;
+  border: 1px solid #444;
+  color: #e0e0e0;
+}
+
+.dark-mode .sphinx-feature a {
+  color: #90caf9;
+}
+
+.dark-mode .sphinx-feature > p.admonition-title {
+  background-color: #2a2a2a !important;
+  color: #ffeb3b;
+}

tests/roots/test-root/wrongenc.inc

@@ -1,3 +1,3 @@
 This file is encoded in latin-1 but at first read as utf-8.
 
-Max Strauß aß in München eine Leberkässemmel.
+Max Strauß aß in München eine Leberkässemmel.

tests/roots/test-warnings/wrongenc.inc

@@ -1,3 +1,3 @@
 This file is encoded in latin-1 but at first read as utf-8.
 
-Max Strauß aß in München eine Leberkässemmel.
+Max Strauß aß in München eine Leberkässemmel.