From d4f5b1377c21a54c862246efce77db601cf58bbd Mon Sep 17 00:00:00 2001
From: squidfunk <martin.donath@squidfunk.com>
Date: Tue, 18 Feb 2020 17:07:20 +0100
Subject: [PATCH] Fixed invalid anchor list offset for hidden anchors

---
 src/assets/javascripts/observables/anchor/index.ts | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/assets/javascripts/observables/anchor/index.ts b/src/assets/javascripts/observables/anchor/index.ts
index 33468a0e6..740240ed0 100644
--- a/src/assets/javascripts/observables/anchor/index.ts
+++ b/src/assets/javascripts/observables/anchor/index.ts
@@ -132,9 +132,18 @@ export function watchAnchorList(
               break
             }
           }
+
+          /* If the current anchor is hidden, continue with its parent */
+          let offset = target.offsetTop
+          while (!offset && target.parentElement) {
+            target = target.parentElement
+            offset = target.offsetTop
+          }
+
+          /* Map reversed anchor path to vertical offset */
           return index.set(
             reverse(path = [...path, anchor]),
-            target.offsetTop
+            offset
           )
         }, new Map<HTMLAnchorElement[], number>())
       }),