From 6ac90b36c82febbd451e411cf1e564ecf018bc36 Mon Sep 17 00:00:00 2001
From: Armin Mehinovic <armin@mui.com>
Date: Tue, 8 Oct 2024 14:35:19 +0200
Subject: [PATCH] Use position instead of a lock flag to determine if the
 scroll value should be changed

---
 .../virtualization/GridVirtualScrollbar.tsx   | 20 +++++++------------
 1 file changed, 7 insertions(+), 13 deletions(-)

diff --git a/packages/x-data-grid/src/components/virtualization/GridVirtualScrollbar.tsx b/packages/x-data-grid/src/components/virtualization/GridVirtualScrollbar.tsx
index e5bf5410f4ccf..912ed05493532 100644
--- a/packages/x-data-grid/src/components/virtualization/GridVirtualScrollbar.tsx
+++ b/packages/x-data-grid/src/components/virtualization/GridVirtualScrollbar.tsx
@@ -70,8 +70,8 @@ const GridVirtualScrollbar = React.forwardRef<HTMLDivElement, GridVirtualScrollb
   function GridVirtualScrollbar(props, ref) {
     const apiRef = useGridPrivateApiContext();
     const rootProps = useGridRootProps();
-    const isLocked = React.useRef(false);
-    const lastPosition = React.useRef(0);
+    const lastPositionScroller = React.useRef(0);
+    const lastPositionScrollbar = React.useRef(0);
     const scrollbarRef = React.useRef<HTMLDivElement>(null);
     const contentRef = React.useRef<HTMLDivElement>(null);
     const classes = useUtilityClasses(rootProps, props.position);
@@ -96,34 +96,28 @@ const GridVirtualScrollbar = React.forwardRef<HTMLDivElement, GridVirtualScrollb
       const scroller = apiRef.current.virtualScrollerRef.current!;
       const scrollbar = scrollbarRef.current!;
 
-      if (scroller[propertyScroll] === lastPosition.current) {
+      if (scroller[propertyScroll] === lastPositionScroller.current) {
         return;
       }
 
-      if (isLocked.current) {
-        isLocked.current = false;
-        return;
-      }
-      isLocked.current = true;
-
       const value = scroller[propertyScroll] / contentSize;
       scrollbar[propertyScroll] = value * scrollbarInnerSize;
 
-      lastPosition.current = scroller[propertyScroll];
+      lastPositionScrollbar.current = scrollbar[propertyScroll];
     });
 
     const onScrollbarScroll = useEventCallback(() => {
       const scroller = apiRef.current.virtualScrollerRef.current!;
       const scrollbar = scrollbarRef.current!;
 
-      if (isLocked.current) {
-        isLocked.current = false;
+      if (scrollbar[propertyScroll] === lastPositionScrollbar.current) {
         return;
       }
-      isLocked.current = true;
 
       const value = scrollbar[propertyScroll] / scrollbarInnerSize;
       scroller[propertyScroll] = value * contentSize;
+
+      lastPositionScroller.current = scroller[propertyScroll];
     });
 
     useOnMount(() => {