Add GUI test for headings anchor

tests/rustdoc-gui/headers-color.goml

@@ -1,4 +1,4 @@
-// This test check for headers text and background colors for the different themes.
+// This test check for headings text and background colors for the different themes.
 
 define-function: (
     "check-colors",
@@ -45,7 +45,7 @@ call-function: (
         "color": "#c5c5c5",
         "code_header_color": "#e6e1cf",
         "focus_background_color": "rgba(255, 236, 164, 0.06)",
-        "headings_color": "#39afd7",
+        "headings_color": "#c5c5c5",
     },
 )
 call-function: (
@@ -55,7 +55,7 @@ call-function: (
         "color": "#ddd",
         "code_header_color": "#ddd",
         "focus_background_color": "#494a3d",
-        "headings_color": "#d2991d",
+        "headings_color": "#ddd",
     },
 )
 call-function: (
@@ -65,6 +65,6 @@ call-function: (
         "color": "black",
         "code_header_color": "black",
         "focus_background_color": "#fdffd3",
-        "headings_color": "#3873ad",
+        "headings_color": "black",
     },
 )

tests/rustdoc-gui/headings-anchor.goml

@@ -0,0 +1,32 @@
+// Test to ensure that the headings anchor behave as expected.
+go-to: "file://" + |DOC_PATH| + "/test_docs/struct.HeavilyDocumentedStruct.html"
+show-text: true
+
+define-function: (
+    "check-heading-anchor",
+    (heading_id),
+    block {
+        // The anchor should not be displayed by default.
+        assert-css: ("#" + |heading_id| + " .doc-anchor", { "display": "none" })
+        // We ensure that hovering the heading makes the anchor visible.
+        move-cursor-to: "#" + |heading_id|
+        assert-css: ("#" + |heading_id| + ":hover .doc-anchor", { "display": "block" })
+        // We then ensure that moving from the heading to the anchor doesn't make the anchor
+        // disappear.
+        move-cursor-to: "#" + |heading_id| + " .doc-anchor"
+        assert-css: ("#" + |heading_id| + " .doc-anchor:hover", {
+            "display": "block",
+            // We also ensure that there is no underline decoration.
+            "text-decoration-line": "none",
+        })
+    }
+)
+
+move-cursor-to: "#top-doc-prose-title"
+// If the top documentation block first element is a heading, we should never display its anchor
+// to prevent it from overlapping with the `[-]` element.
+assert-css: ("#top-doc-prose-title:hover .doc-anchor", { "display": "none" })
+
+call-function: ("check-heading-anchor", ("top-doc-prose-sub-heading"))
+call-function: ("check-heading-anchor", ("top-doc-prose-sub-sub-heading"))
+call-function: ("check-heading-anchor", ("you-know-the-drill"))