book.toml

@@ -18,4 +18,5 @@ additional-js = [
     "theme/js/highlight.min.js",
     "theme/js/mathjax.js",
     "theme/js/tocrender.js",
+    "theme/js/page.js",
 ]

theme/index.hbs

@@ -84,7 +84,7 @@
             {{/if}}
         </mdui-top-app-bar>
 
-        <mdui-navigation-drawer close-on-overlay-click class="toc-drawer" id="toc-drawer" placement="left" open>
+        <mdui-navigation-drawer close-on-overlay-click class="toc-drawer" id="toc-drawer" placement="left">
         </mdui-navigation-drawer>
         {{/unless}}
 
@@ -201,6 +201,8 @@
 
     <script>hljs.highlightAll();</script>
 
+    <script src="{{ ../path_to_root }}theme/js/page.js"></script>
+
 </body>
 
 </html>

theme/js/page.js

@@ -0,0 +1,3 @@
+if (window.innerWidth > 640) {
+    document.getElementById("toc-drawer").setAttribute('open', true)
+}