From 38cecddcd18892fc48b407f1bf94d466305e1e35 Mon Sep 17 00:00:00 2001
From: Raymond Hill <rhill@raymondhill.net>
Date: Wed, 18 Nov 2020 14:11:36 -0500
Subject: [PATCH] Improve zapper's detection of scroll-locked documents

---
 src/js/scriptlets/epicker.js | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/src/js/scriptlets/epicker.js b/src/js/scriptlets/epicker.js
index f0b37e3e6..02f625225 100644
--- a/src/js/scriptlets/epicker.js
+++ b/src/js/scriptlets/epicker.js
@@ -921,12 +921,12 @@ const zapElementAtPoint = function(mx, my, options) {
         return;
     }
 
-    let elem = targetElements.length !== 0 && targetElements[0] || null;
-    if ( elem === null && mx !== undefined ) {
-        elem = elementFromPoint(mx, my);
+    let elemToRemove = targetElements.length !== 0 && targetElements[0] || null;
+    if ( elemToRemove === null && mx !== undefined ) {
+        elemToRemove = elementFromPoint(mx, my);
     }
 
-    if ( elem instanceof Element === false ) { return; }
+    if ( elemToRemove instanceof Element === false ) { return; }
 
     const getStyleValue = function(elem, prop) {
         const style = window.getComputedStyle(elem);
@@ -934,23 +934,30 @@ const zapElementAtPoint = function(mx, my, options) {
     };
 
     // Heuristic to detect scroll-locking: remove such lock when detected.
-    if (
-        parseInt(getStyleValue(elem, 'zIndex'), 10) >= 1000 ||
-        getStyleValue(elem, 'position') === 'fixed'
-    ) {
+    let maybeScrollLocked = false;
+    let elem = elemToRemove;
+    do {
+        maybeScrollLocked =
+            parseInt(getStyleValue(elem, 'zIndex'), 10) >= 1000 ||
+            getStyleValue(elem, 'position') === 'fixed';
+        elem = elem.parentElement;
+    } while ( elem !== null && maybeScrollLocked === false );
+    if ( maybeScrollLocked ) {
         const doc = document;
         if ( getStyleValue(doc.body, 'overflowY') === 'hidden' ) {
             doc.body.style.setProperty('overflow', 'auto', 'important');
         }
         if ( getStyleValue(doc.body, 'position') === 'fixed' ) {
-            doc.body.style.setProperty('position', 'static', 'important');
+            doc.body.style.setProperty('position', 'initial', 'important');
+        }
+        if ( getStyleValue(doc.documentElement, 'position') === 'fixed' ) {
+            doc.documentElement.style.setProperty('position', 'initial', 'important');
         }
         if ( getStyleValue(doc.documentElement, 'overflowY') === 'hidden' ) {
             doc.documentElement.style.setProperty('overflow', 'auto', 'important');
         }
     }
-
-    elem.remove();
+    elemToRemove.remove();
     highlightElementAtPoint(mx, my);
 };