Rollup merge of #115660 - notriddle:notriddle/sidebar-resize, r=GuillaumeGomez

rustdoc: allow resizing the sidebar / hiding the top bar

Fixes #97306

Preview: http://notriddle.com/rustdoc-html-demo-4/sidebar-resize/std/index.html

![image](https://github.com/rust-lang/rust/assets/1593513/a2f40ea2-0436-4e44-99e8-d160dab2a680)

## Summary

This feature adds:

1. A checkbox to the Settings popover to hide the persistent navigation bar (the sidebar on large viewports and the top bar on small ones).
2. On large viewports, it adds a resize handle to the persistent sidebar. Resizing it into nothing is equivalent to turning off the persistent navigation bar checkbox in Settings.
3. If the navigation bar is hidden, a toolbar button to the left of the search appears. Clicking it brings the navigation bar back.

## Motivation

While "mobile mode" is definitely a good default, it's not the only reason people have wanted to hide the sidebar:

* Some people use tiling window managers, and don't like rustdoc's current breakpoints. Changing the breakpoints might help with that, but there's no perfect solution, because there's a gap between "huge screen" and "smartphone" where reasonable people can disagree about whether it makes sense for the sidebar to be on-screen. https://github.com/rust-lang/rust/issues/97306

* Some people ask for ways to reduce on-screen clutter because it makes it easier to focus. There's not a media query for that (and if there was, privacy-conscious users would turn it off). https://github.com/rust-lang/rust/issues/59829

This feature is designed to avoid these problems. Resizing the sidebar especially helps, because it provides a way to hide the sidebar without adding a new top-level button (which would add clutter), and it provides a way to make rustdoc play nicer in complex, custom screen layouts.

## Guide and Reference-level explanation

On a desktop or laptop with a mouse, resize the sidebar by dragging its right edge.

On any browser, including mobile phones, the sticky top bar or side bar can be hidden from the Settings area (the button with the cog wheel, next to the search bar). When it's hidden, a convenient button will appear on the search bar's left.

## Drawbacks

This adds more JavaScript code to the render blocking area.

## Rationale and alternatives

The most obvious way to allow people to hide the sidebar would have been to let them "manually enter mobile mode." The upside is that it's a feature we already have. The downside is that it's actually really hard to come up with a terse description. Is it:

* A Setting that forces desktop viewers to always have the mobile-style top bar? If so, how do we label it? Should it be visible on mobile, and, if so, does it just not do anything?
* A persistent hide/show sidebar button, present on desktop, just like on mobile? That's clutter that I'd like to avoid.

## Prior art

* The new file browser in GitHub uses a similar divider with a mouse-over indicator
* mdBook and macOS Finder both allow you to resize the sidebar to nothing as a gesture to hide it
* https://www.nngroup.com/articles/drag-drop/

## Future possibilities

https://rust-lang.zulipchat.com/#narrow/stream/266220-rustdoc/topic/Table.20of.20contents proposes a new, second sidebar (a table of contents). How should it fit in with this feature? Should it be resizeable? Hideable? Can it be accessed on mobile?

2 files changed, 167 insertions, 10 deletions

diff --git a/src/librustdoc/html/static/css/noscript.css b/src/librustdoc/html/static/css/noscript.css
index fe0cf6dc8cc..390e812772a 100644
--- a/src/librustdoc/html/static/css/noscript.css
+++ b/src/librustdoc/html/static/css/noscript.css
@@ -9,7 +9,7 @@ rules.
 	margin-left: 0 !important;
 }
 
-#copy-path {
+#copy-path, #sidebar-button, .sidebar-resizer {
 	/* It requires JS to work so no need to display it in this case. */
 	display: none;
 }
@@ -132,6 +132,8 @@ nav.sub {
 	--scrape-example-help-hover-color: #000;
 	--scrape-example-code-wrapper-background-start: rgba(255, 255, 255, 1);
 	--scrape-example-code-wrapper-background-end: rgba(255, 255, 255, 0);
+	--sidebar-resizer-hover: hsl(207, 90%, 66%);
+	--sidebar-resizer-active: hsl(207, 90%, 54%);
 }
 /* End theme: light */
 
@@ -238,6 +240,8 @@ nav.sub {
 		--scrape-example-help-hover-color: #fff;
 		--scrape-example-code-wrapper-background-start: rgba(53, 53, 53, 1);
 		--scrape-example-code-wrapper-background-end: rgba(53, 53, 53, 0);
+		--sidebar-resizer-hover: hsl(207, 30%, 54%);
+		--sidebar-resizer-active: hsl(207, 90%, 54%);
 	}
 /* End theme: dark */
 }
diff --git a/src/librustdoc/html/static/css/rustdoc.css b/src/librustdoc/html/static/css/rustdoc.css
index 6e61969a8c1..6e673aa77c5 100644
--- a/src/librustdoc/html/static/css/rustdoc.css
+++ b/src/librustdoc/html/static/css/rustdoc.css
@@ -9,6 +9,11 @@
 :root {
 	--nav-sub-mobile-padding: 8px;
 	--search-typename-width: 6.75rem;
+	/* DEFAULT_SIDEBAR_WIDTH
+	   see main.js for information on these values
+	   and on the RUSTDOC_MOBILE_BREAKPOINT */
+	--desktop-sidebar-width: 200px;
+	--src-sidebar-width: 300px;
 }
 
 /* See FiraSans-LICENSE.txt for the Fira Sans license. */
@@ -383,13 +388,15 @@ img {
 
 .sidebar {
 	font-size: 0.875rem;
-	flex: 0 0 200px;
+	flex: 0 0 var(--desktop-sidebar-width);
+	width: var(--desktop-sidebar-width);
 	overflow-y: scroll;
 	overscroll-behavior: contain;
 	position: sticky;
 	height: 100vh;
 	top: 0;
 	left: 0;
+	z-index: 100;
 }
 
 .rustdoc.src .sidebar {
@@ -398,7 +405,95 @@ img {
 	overflow-x: hidden;
 	/* The sidebar is by default hidden  */
 	overflow-y: hidden;
-	z-index: 1;
+}
+
+.hide-sidebar .sidebar,
+.hide-sidebar .sidebar-resizer {
+	display: none;
+}
+
+.sidebar-resizer {
+	touch-action: none;
+	width: 9px;
+	cursor: col-resize;
+	z-index: 200;
+	position: fixed;
+	height: 100%;
+	/* make sure there's a 1px gap between the scrollbar and resize handle */
+	left: calc(var(--desktop-sidebar-width) + 1px);
+}
+
+.rustdoc.src .sidebar-resizer {
+	/* when closed, place resizer glow on top of the normal src sidebar border (no need to worry
+	   about sidebar) */
+	left: 49px;
+}
+
+.src-sidebar-expanded .rustdoc.src .sidebar-resizer {
+	/* for src sidebar, gap is already provided by 1px border on sidebar itself, so place resizer
+	   to right of it */
+	left: var(--src-sidebar-width);
+}
+
+.sidebar-resizing {
+	-moz-user-select: none;
+	-webkit-user-select: none;
+	-ms-user-select: none;
+	user-select: none;
+}
+
+.sidebar-resizing * {
+	cursor: col-resize !important;
+}
+
+.sidebar-resizing .sidebar {
+	position: fixed;
+	z-index: 100;
+}
+.sidebar-resizing > body {
+	padding-left: var(--resizing-sidebar-width);
+}
+
+.sidebar-resizer:hover,
+.sidebar-resizer:active,
+.sidebar-resizer:focus,
+.sidebar-resizer.active {
+	width: 10px;
+	margin: 0;
+	/* when active or hovered, place resizer glow on top of the sidebar (right next to, or even
+	   on top of, the scrollbar) */
+	left: var(--desktop-sidebar-width);
+	border-left: solid 1px var(--sidebar-resizer-hover);
+}
+
+.src-sidebar-expanded .rustdoc.src .sidebar-resizer:hover,
+.src-sidebar-expanded .rustdoc.src .sidebar-resizer:active,
+.src-sidebar-expanded .rustdoc.src .sidebar-resizer:focus,
+.src-sidebar-expanded .rustdoc.src .sidebar-resizer.active {
+	/* when active or hovered, place resizer glow on top of the normal src sidebar border */
+	left: calc(var(--src-sidebar-width) - 1px);
+}
+
+@media (pointer: coarse) {
+	.sidebar-resizer {
+		/* too easy to hit the resizer while trying to hit the [-] toggle */
+		display: none !important;
+	}
+}
+
+.sidebar-resizer.active {
+	/* make the resize tool bigger when actually resizing, to avoid :hover styles on other stuff
+		while resizing */
+	padding: 0 140px;
+	width: 2px;
+	margin-left: -140px;
+	border-left: none;
+}
+.sidebar-resizer.active:before {
+	border-left: solid 2px var(--sidebar-resizer-active);
+	display: block;
+	height: 100%;
+	content: "";
 }
 
 .sidebar, .mobile-topbar, .sidebar-menu-toggle,
@@ -416,7 +511,8 @@ img {
 
 .src-sidebar-expanded .src .sidebar {
 	overflow-y: auto;
-	flex-basis: 300px;
+	flex-basis: var(--src-sidebar-width);
+	width: var(--src-sidebar-width);
 }
 
 .src-sidebar-expanded .src .sidebar > *:not(#src-sidebar-toggle) {
@@ -477,6 +573,7 @@ ul.block, .block li {
 	display: block;
 	padding: 0.25rem; /* 4px */
 	margin-left: -0.25rem;
+	margin-right: 0.25rem;
 }
 
 .sidebar h2 {
@@ -775,7 +872,7 @@ h2.section-header > .anchor {
 	text-decoration: underline;
 }
 
-.crate.block a.current { font-weight: 500; }
+.crate.block li.current a { font-weight: 500; }
 
 /*  In most contexts we use `overflow-wrap: anywhere` to ensure that we can wrap
 	as much as needed on mobile (see
@@ -1478,7 +1575,20 @@ a.tooltip:hover::after {
 	margin-left: 4px;
 	display: flex;
 }
-#settings-menu > a, #help-button > a {
+#sidebar-button {
+	display: none;
+}
+.hide-sidebar #sidebar-button {
+	display: flex;
+	margin-right: 4px;
+	position: fixed;
+	left: 6px;
+	height: 34px;
+	width: 34px;
+	background-color: var(--main-background-color);
+	z-index: 1;
+}
+#settings-menu > a, #help-button > a, #sidebar-button > a {
 	display: flex;
 	align-items: center;
 	justify-content: center;
@@ -1493,10 +1603,21 @@ a.tooltip:hover::after {
 }
 
 #settings-menu > a:hover, #settings-menu > a:focus,
-#help-button > a:hover, #help-button > a:focus {
+#help-button > a:hover, #help-button > a:focus,
+#sidebar-button > a:hover, #sidebar-button > a:focus {
 	border-color: var(--settings-button-border-focus);
 }
 
+#sidebar-button > a:before {
+	content: url('data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 22 22" \
+		fill="none" stroke="black">\
+		<rect x="1" y="1" width="20" height="20" ry="1.5" stroke-width="1.5"/>\
+		<circle cx="4.375" cy="4.375" r="1" stroke-width=".75"/>\
+		<path d="m7.6121 3v16 M5.375 7.625h-2 m2 3h-2 m2 3h-2" stroke-width="1.25"/></svg>');
+	width: 22px;
+	height: 22px;
+}
+
 #copy-path {
 	color: var(--copy-path-button-color);
 	background: var(--main-background-color);
@@ -1711,7 +1832,7 @@ However, it's not needed with smaller screen width because the doc/code block is
 /*
 WARNING: RUSTDOC_MOBILE_BREAKPOINT MEDIA QUERY
 If you update this line, then you also need to update the line with the same warning
-in src-script.js
+in src-script.js and main.js
 */
 @media (max-width: 700px) {
 	/* When linking to an item with an `id` (for instance, by clicking a link in the sidebar,
@@ -1722,6 +1843,10 @@ in src-script.js
 		scroll-margin-top: 45px;
 	}
 
+	.hide-sidebar #sidebar-button {
+		position: static;
+	}
+
 	.rustdoc {
 		/* Sidebar should overlay main content, rather than pushing main content to the right.
 		   Turn off `display: flex` on the body element. */
@@ -1750,7 +1875,8 @@ in src-script.js
 	/* Hide the logo and item name from the sidebar. Those are displayed
 	   in the mobile-topbar instead. */
 	.sidebar .logo-container,
-	.sidebar .location {
+	.sidebar .location,
+	.sidebar-resizer {
 		display: none;
 	}
 
@@ -1818,6 +1944,10 @@ in src-script.js
 		top: 0;
 	}
 
+	.hide-sidebar .mobile-topbar {
+		display: none;
+	}
+
 	.sidebar-menu-toggle {
 		width: 45px;
 		/* Rare exception to specifying font sizes in rem. Since this is acting
@@ -1827,6 +1957,10 @@ in src-script.js
 		color: var(--main-color);
 	}
 
+	.hide-sidebar .sidebar-menu-toggle {
+		display: none;
+	}
+
 	.sidebar-elems {
 		margin-top: 1em;
 	}
@@ -1870,6 +2004,17 @@ in src-script.js
 		display: none;
 	}
 
+	/* sidebar button becomes topbar button */
+	#sidebar-button > a:before {
+		content: url('data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg" \
+			viewBox="0 0 22 22" fill="none" stroke="black">\
+			<rect x="1" y="1" width="20" height="20" ry="1.5" stroke-width="1.5"/>\
+			<circle cx="4.375" cy="4.375" r="1" stroke-width=".75"/>\
+			<path d="m3 7.375h16m0-3h-4" stroke-width="1.25"/></svg>');
+		width: 22px;
+		height: 22px;
+	}
+
 	/* Display an alternating layout on tablets and phones */
 	.item-table, .item-row, .item-table > li, .item-table > li > div,
 	.search-results > a, .search-results > a > div {
@@ -2274,6 +2419,8 @@ in src-script.js
 	--scrape-example-help-hover-color: #000;
 	--scrape-example-code-wrapper-background-start: rgba(255, 255, 255, 1);
 	--scrape-example-code-wrapper-background-end: rgba(255, 255, 255, 0);
+	--sidebar-resizer-hover: hsl(207, 90%, 66%);
+	--sidebar-resizer-active: hsl(207, 90%, 54%);
 }
 /* End theme: light */
 
@@ -2379,6 +2526,8 @@ in src-script.js
 	--scrape-example-help-hover-color: #fff;
 	--scrape-example-code-wrapper-background-start: rgba(53, 53, 53, 1);
 	--scrape-example-code-wrapper-background-end: rgba(53, 53, 53, 0);
+	--sidebar-resizer-hover: hsl(207, 30%, 54%);
+	--sidebar-resizer-active: hsl(207, 90%, 54%);
 }
 /* End theme: dark */
 
@@ -2488,6 +2637,8 @@ Original by Dempfi (https://github.com/dempfi/ayu)
 	--scrape-example-help-hover-color: #fff;
 	--scrape-example-code-wrapper-background-start: rgba(15, 20, 25, 1);
 	--scrape-example-code-wrapper-background-end: rgba(15, 20, 25, 0);
+	--sidebar-resizer-hover: hsl(34, 50%, 33%);
+	--sidebar-resizer-active: hsl(34, 100%, 66%);
 }
 
 :root[data-theme="ayu"] h1,
@@ -2519,6 +2670,7 @@ Original by Dempfi (https://github.com/dempfi/ayu)
 }
 
 :root[data-theme="ayu"] .sidebar .current,
+:root[data-theme="ayu"] .sidebar .current a,
 :root[data-theme="ayu"] .sidebar a:hover,
 :root[data-theme="ayu"] #src-sidebar div.files > a:hover,
 :root[data-theme="ayu"] details.dir-entry summary:hover,
@@ -2569,7 +2721,8 @@ Original by Dempfi (https://github.com/dempfi/ayu)
 	border-bottom: 1px solid rgba(242, 151, 24, 0.3);
 }
 
-:root[data-theme="ayu"] #settings-menu > a img {
+:root[data-theme="ayu"] #settings-menu > a img,
+:root[data-theme="ayu"] #sidebar-button > a:before {
 	filter: invert(100);
 }
 /* End theme: ayu */