Rollup merge of #98310 - jsha:defer-source-sidebar, r=GuillaumeGomez

rustdoc: optimize loading of source sidebar

The source sidebar has a setting to remember whether it should be open or
closed. Previously, this setting was handled in source-script.js, which
is loaded with `defer`, meaning it is often run after the document is rendered.
Since CSS renders the source sidebar as closed by default, changing this
after the initial render results in a relayout.

Instead, handle the setting in storage.js, which is the first script to load
and is the only script that blocks render. This avoids a relayout and means
navigating between files with the sidebar open is faster.

Demo: https://rustdoc.crud.net/jsha/defer-source-sidebar/src/alloc/ffi/c_str.rs.html

r? ````@GuillaumeGomez````

1 files changed, 2 insertions, 8 deletions

diff --git a/src/librustdoc/html/static/js/source-script.js b/src/librustdoc/html/static/js/source-script.js
index 10f93a1c058..290c29d3141 100644
--- a/src/librustdoc/html/static/js/source-script.js
+++ b/src/librustdoc/html/static/js/source-script.js
@@ -63,14 +63,13 @@ function createDirEntry(elem, parent, fullPath, hasFoundFile) {
 }
 
 function toggleSidebar() {
-    const sidebar = document.querySelector("nav.sidebar");
     const child = this.children[0];
     if (child.innerText === ">") {
-        sidebar.classList.add("expanded");
+        addClass(document.documentElement, "source-sidebar-expanded");
         child.innerText = "<";
         updateLocalStorage("source-sidebar-show", "true");
     } else {
-        sidebar.classList.remove("expanded");
+        removeClass(document.documentElement, "source-sidebar-expanded");
         child.innerText = ">";
         updateLocalStorage("source-sidebar-show", "false");
     }
@@ -103,11 +102,6 @@ function createSourceSidebar() {
 
     const sidebar = document.createElement("div");
     sidebar.id = "source-sidebar";
-    if (getCurrentValue("source-sidebar-show") !== "true") {
-        container.classList.remove("expanded");
-    } else {
-        container.classList.add("expanded");
-    }
 
     let hasFoundFile = false;