Rollup merge of rust-lang#87167 - GuillaumeGomez:sidebar-display-mobile, r=notriddle

Fix sidebar display on small devices

Part of rust-lang#87059.

Instead of hiding the sidebar on small devices, we instead move it out of the viewport so that it remains "visible" to our text only users.

Could you confirm it works for you `@ahicks92` and `@DataTriny` please? You can give it a try at [this URL](https://guillaume-gomez.fr/rustdoc-test/test_docs/index.html).

r? `@notriddle`

Author: GuillaumeGomez

src/librustdoc/html/static/css/rustdoc.css

@@ -1634,15 +1634,18 @@ details.undocumented[open] > summary::before {
 		display: none;
 	}
 
+	/* We do NOT hide this element so that alternative device readers still have this information
+	   available. */
 	.sidebar-elems {
 		position: fixed;
 		z-index: 1;
-		left: 0;
 		top: 45px;
 		bottom: 0;
+		width: 246px;
+		/* We move the sidebar to the left by its own width so it doesn't appear. */
+		left: -246px;
 		overflow-y: auto;
 		border-right: 1px solid;
-		display: none;
 	}
 
 	.sidebar > .block.version {
@@ -1730,8 +1733,7 @@ details.undocumented[open] > summary::before {
 	}
 
 	.show-it {
-		display: block;
-		width: 246px;
+		left: 0;
 	}
 
 	.show-it > .block.items {

src/test/rustdoc-gui/sidebar-mobile.goml

@@ -0,0 +1,10 @@
+// This test ensure that the sidebar isn't "hidden" on mobile but instead moved out of the viewport.
+// This is especially important for devices for "text-first" content (like for users with
+// sight issues).
+goto: file://|DOC_PATH|/test_docs/struct.Foo.html
+// Switching to "mobile view" by reducing the width to 600px.
+size: (600, 600)
+assert-css: (".sidebar-elems", {"display": "block", "left": "-246px"})
+// Opening the sidebar menu.
+click: ".sidebar-menu"
+assert-css: (".sidebar-elems", {"display": "block", "left": "0px"})