rustdoc: use consistent "popover" styling for notable traits

src/librustdoc/html/render/mod.rs

@@ -1312,9 +1312,7 @@ pub(crate) fn notable_traits_button(ty: &clean::Type, cx: &mut Context<'_>) -> O
     if has_notable_trait {
         cx.types_with_notable_traits.insert(ty.clone());
         Some(format!(
-            "<span class=\"notable-traits\" data-ty=\"{ty}\">\
-                <span class=\"notable-traits-tooltip\">ⓘ</span>\
-            </span>",
+            " <a href=\"#\" class=\"notable-traits\" data-ty=\"{ty}\">ⓘ</a>",
             ty = Escape(&format!("{:#}", ty.print(cx))),
         ))
     } else {
@@ -1343,7 +1341,7 @@ fn notable_traits_decl(ty: &clean::Type, cx: &Context<'_>) -> (String, String) {
                 if out.is_empty() {
                     write!(
                         &mut out,
-                        "<h3 class=\"notable\">Notable traits for <code>{}</code></h3>\
+                        "<h3>Notable traits for <code>{}</code></h3>\
                      <pre class=\"content\"><code>",
                         impl_.for_.print(cx)
                     );

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

@@ -183,8 +183,6 @@ h4.code-header {
 	font-weight: 600;
 	margin: 0;
 	padding: 0;
-	/* position notable traits in mobile mode within the header */
-	position: relative;
 }
 
 #crate-search,
@@ -930,13 +928,14 @@ so that we can apply CSS-filters to change the arrow color in themes */
 	border-radius: 3px;
 	border: 1px solid var(--border-color);
 	font-size: 1rem;
+	--popover-arrow-offset: 11px;
 }
 
 /* This rule is to draw the little arrow connecting the settings menu to the gear icon. */
 .popover::before {
 	content: '';
 	position: absolute;
-	right: 11px;
+	right: var(--popover-arrow-offset);
 	border: solid var(--border-color);
 	border-width: 1px 1px 0 0;
 	display: inline-block;
@@ -953,10 +952,7 @@ so that we can apply CSS-filters to change the arrow color in themes */
 /* use larger max-width for help popover, but not for help.html */
 #help.popover {
 	max-width: 600px;
-}
-
-#help.popover::before {
-	right: 48px;
+	--popover-arrow-offset: 48px;
 }
 
 #help dt {
@@ -1275,54 +1271,34 @@ h3.variant {
 	border-right: 3px solid var(--target-border-color);
 }
 
-.notable-traits-tooltip {
-	display: inline-block;
-	cursor: pointer;
-}
-
-.notable-traits .notable-traits-tooltiptext {
-	display: inline-block;
-	visibility: hidden;
+.notable-traits {
+	color: inherit;
+	margin-right: 15px;
+	position: relative;
 }
 
-.notable-traits-tooltiptext {
-	padding: 5px 3px 3px 3px;
-	border-radius: 6px;
-	margin-left: 5px;
-	z-index: 10;
-	font-size: 1rem;
-	cursor: default;
+/* placeholder thunk so that the mouse can easily travel from "(i)" to popover
+	the resulting "hover tunnel" is a stepped triangle, approximating
+	https://bjk5.com/post/44698559168/breaking-down-amazons-mega-dropdown */
+.notable-traits:hover::after {
 	position: absolute;
-	border: 1px solid;
-}
-
-.notable-traits-tooltip::after {
-	/* The margin on the tooltip does not capture hover events,
-	   this extends the area of hover enough so that mouse hover is not
-	   lost when moving the mouse to the tooltip */
-	content: "\00a0\00a0\00a0";
-}
-
-.notable-traits-tooltiptext .docblock {
-	margin: 0;
+	top: calc(100% - 10px);
+	left: -15px;
+	right: -15px;
+	height: 20px;
+	content: "\00a0";
 }
 
-.notable-traits-tooltiptext .notable {
-	font-size: 1.1875rem;
-	font-weight: 600;
-	display: block;
+.notable .docblock {
+	margin: 0.25em 0.5em;
 }
 
-.notable-traits-tooltiptext pre, .notable-traits-tooltiptext code {
+.notable .docblock pre, .notable .docblock code {
 	background: transparent;
-}
-
-.notable-traits-tooltiptext .docblock pre.content {
 	margin: 0;
 	padding: 0;
 	font-size: 1.25rem;
 	white-space: pre-wrap;
-	overflow: hidden;
 }
 
 .search-failed {
@@ -1365,12 +1341,6 @@ h3.variant {
 	font-size: 1rem;
 }
 
-.notable-traits {
-	cursor: pointer;
-	z-index: 2;
-	margin-left: 5px;
-}
-
 #sidebar-toggle {
 	position: sticky;
 	top: 0;
@@ -1855,11 +1825,6 @@ in storage.js
 		border-bottom: 1px solid;
 	}
 
-	.notable-traits .notable-traits-tooltiptext {
-		left: 0;
-		top: 100%;
-	}
-
 	/* We don't display the help button on mobile devices. */
 	#help-button {
 		display: none;

src/librustdoc/html/static/css/themes/ayu.css

@@ -183,10 +183,6 @@ details.rustdoc-toggle > summary::before {
 	border-color: transparent #314559 transparent transparent;
 }
 
-.notable-traits-tooltiptext {
-	background-color: #314559;
-}
-
 #titles > button.selected {
 	background-color: #141920 !important;
 	border-bottom: 1px solid #ffb44c !important;

src/librustdoc/html/static/css/themes/dark.css

@@ -106,10 +106,6 @@ details.rustdoc-toggle > summary::before {
 	border-color: transparent black transparent transparent;
 }
 
-.notable-traits-tooltiptext {
-	background-color: #111;
-}
-
 #titles > button:not(.selected) {
 	background-color: #252525;
 	border-top-color: #252525;

src/librustdoc/html/static/css/themes/light.css

@@ -98,10 +98,6 @@ body.source .example-wrap pre.rust a {
 	border-color: transparent black transparent transparent;
 }
 
-.notable-traits-tooltiptext {
-	background-color: #eee;
-}
-
 #titles > button:not(.selected) {
 	background-color: #e6e6e6;
 	border-top-color: #e6e6e6;

src/librustdoc/html/static/js/main.js

@@ -850,18 +850,33 @@ function loadCss(cssUrl) {
         }
         hideNotable();
         const ty = e.getAttribute("data-ty");
-        const tooltip = e.getElementsByClassName("notable-traits-tooltip")[0];
         const wrapper = document.createElement("div");
         wrapper.innerHTML = "<div class=\"docblock\">" + window.NOTABLE_TRAITS[ty] + "</div>";
-        wrapper.className = "notable-traits-tooltiptext";
-        tooltip.appendChild(wrapper);
-        const pos = wrapper.getBoundingClientRect();
-        tooltip.removeChild(wrapper);
-        wrapper.style.top = (pos.top + window.scrollY) + "px";
-        wrapper.style.left = (pos.left + window.scrollX) + "px";
-        wrapper.style.width = pos.width + "px";
+        wrapper.className = "notable popover";
+        const focusCatcher = document.createElement("div");
+        focusCatcher.setAttribute("tabindex", "0");
+        focusCatcher.onfocus = hideNotable;
+        wrapper.appendChild(focusCatcher);
+        const pos = e.getBoundingClientRect();
+        // 5px overlap so that the mouse can easily travel from place to place
+        wrapper.style.top = (pos.top + window.scrollY + pos.height) + "px";
+        wrapper.style.left = 0;
+        wrapper.style.right = "auto";
+        wrapper.style.visibility = "hidden";
         const body = document.getElementsByTagName("body")[0];
         body.appendChild(wrapper);
+        const wrapperPos = wrapper.getBoundingClientRect();
+        // offset so that the arrow points at the center of the "(i)"
+        const finalPos = pos.left + window.scrollX - wrapperPos.width + 24;
+        if (finalPos > 0) {
+            wrapper.style.left = finalPos + "px";
+        } else {
+            wrapper.style.setProperty(
+                "--popover-arrow-offset",
+                (wrapperPos.right - pos.right + 4) + "px"
+            );
+        }
+        wrapper.style.visibility = "";
         window.CURRENT_NOTABLE_ELEMENT = wrapper;
         window.CURRENT_NOTABLE_ELEMENT.NOTABLE_BASE = e;
         wrapper.onpointerleave = function(ev) {
@@ -875,9 +890,31 @@ function loadCss(cssUrl) {
         };
     }
 
+    function notableBlurHandler(event) {
+        if (window.CURRENT_NOTABLE_ELEMENT &&
+            !elemIsInParent(document.activeElement, window.CURRENT_NOTABLE_ELEMENT) &&
+            !elemIsInParent(event.relatedTarget, window.CURRENT_NOTABLE_ELEMENT) &&
+            !elemIsInParent(document.activeElement, window.CURRENT_NOTABLE_ELEMENT.NOTABLE_BASE) &&
+            !elemIsInParent(event.relatedTarget, window.CURRENT_NOTABLE_ELEMENT.NOTABLE_BASE)
+        ) {
+            // Work around a difference in the focus behaviour between Firefox, Chrome, and Safari.
+            // When I click the button on an already-opened notable trait popover, Safari
+            // hides the popover and then immediately shows it again, while everyone else hides it
+            // and it stays hidden.
+            //
+            // To work around this, make sure the click finishes being dispatched before
+            // hiding the popover. Since `hideNotable()` is idempotent, this makes Safari behave
+            // consistently with the other two.
+            setTimeout(hideNotable, 0);
+        }
+    }
+
     function hideNotable() {
         if (window.CURRENT_NOTABLE_ELEMENT) {
-            window.CURRENT_NOTABLE_ELEMENT.NOTABLE_BASE.NOTABLE_FORCE_VISIBLE = false;
+            if (window.CURRENT_NOTABLE_ELEMENT.NOTABLE_BASE.NOTABLE_FORCE_VISIBLE) {
+                window.CURRENT_NOTABLE_ELEMENT.NOTABLE_BASE.focus();
+                window.CURRENT_NOTABLE_ELEMENT.NOTABLE_BASE.NOTABLE_FORCE_VISIBLE = false;
+            }
             const body = document.getElementsByTagName("body")[0];
             body.removeChild(window.CURRENT_NOTABLE_ELEMENT);
             window.CURRENT_NOTABLE_ELEMENT = null;
@@ -891,7 +928,11 @@ function loadCss(cssUrl) {
                 hideNotable();
             } else {
                 showNotable(this);
+                window.CURRENT_NOTABLE_ELEMENT.setAttribute("tabindex", "0");
+                window.CURRENT_NOTABLE_ELEMENT.focus();
+                window.CURRENT_NOTABLE_ELEMENT.onblur = notableBlurHandler;
             }
+            return false;
         };
         e.onpointerenter = function(ev) {
             // If this is a synthetic touch event, ignore it. A click event will be along shortly.
@@ -1018,6 +1059,7 @@ function loadCss(cssUrl) {
         onEachLazy(document.querySelectorAll(".search-form .popover"), elem => {
             elem.style.display = "none";
         });
+        hideNotable();
     };
 
     /**