From 83678709f32c8f7e0e83efd93e4a493d1154bd6e Mon Sep 17 00:00:00 2001
From: crupest <crupest@outlook.com>
Date: Sun, 4 Apr 2021 14:43:26 +0800
Subject: ...

---
 .../utilities/useReverseScrollPositionRemember.ts  | 33 ++++++++++++++++++++++
 1 file changed, 33 insertions(+)
 create mode 100644 FrontEnd/src/app/utilities/useReverseScrollPositionRemember.ts

(limited to 'FrontEnd/src/app/utilities')

diff --git a/FrontEnd/src/app/utilities/useReverseScrollPositionRemember.ts b/FrontEnd/src/app/utilities/useReverseScrollPositionRemember.ts
new file mode 100644
index 00000000..8a2bd7a0
--- /dev/null
+++ b/FrontEnd/src/app/utilities/useReverseScrollPositionRemember.ts
@@ -0,0 +1,33 @@
+import React from "react";
+
+let on = false;
+
+export default function useReverseScrollPositionRemember(): void {
+  React.useEffect(() => {
+    if (on) return;
+    on = true;
+
+    let scrollPosition =
+      document.documentElement.scrollHeight -
+      document.documentElement.scrollTop;
+
+    const scrollListener = (): void => {
+      scrollPosition = document.documentElement.scrollHeight - window.scrollY;
+    };
+
+    window.addEventListener("scroll", scrollListener);
+
+    const resizeObserver = new ResizeObserver(() => {
+      document.documentElement.scrollTop =
+        document.documentElement.scrollHeight - scrollPosition;
+    });
+
+    resizeObserver.observe(document.documentElement);
+
+    return () => {
+      window.removeEventListener("scroll", scrollListener);
+      resizeObserver.disconnect();
+      on = false;
+    };
+  }, []);
+}
-- 
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