From e12ff2cef5fc13923ffb8a4ba6417e0cfa879418 Mon Sep 17 00:00:00 2001
From: Roman Vyakhirev <roman.vyakhirev@mendix.com>
Date: Wed, 22 Oct 2025 11:57:12 +0200
Subject: [PATCH] chore: improve virtual scrolling

---
 .../datawidgets/web/_datagrid.scss            |  45 +++++---
 .../datagrid-web/CHANGELOG.md                 |   4 +
 .../datagrid-web/src/components/Grid.tsx      |  25 ++++-
 .../datagrid-web/src/components/GridBody.tsx  |  30 ++----
 .../src/components/GridHeader.tsx             |   8 +-
 .../datagrid-web/src/components/Widget.tsx    |  20 +++-
 .../src/components/InfiniteBody.tsx           | 100 +++++++++++-------
 7 files changed, 144 insertions(+), 88 deletions(-)

diff --git a/packages/modules/data-widgets/src/themesource/datawidgets/web/_datagrid.scss b/packages/modules/data-widgets/src/themesource/datawidgets/web/_datagrid.scss
index e6ecaea017..737591eada 100644
--- a/packages/modules/data-widgets/src/themesource/datawidgets/web/_datagrid.scss
+++ b/packages/modules/data-widgets/src/themesource/datawidgets/web/_datagrid.scss
@@ -394,21 +394,14 @@ $root: ".widget-datagrid";
             display: grid !important;
             min-width: fit-content;
             margin-bottom: 0;
+            &.infinite-loading {
+                // in order to restrict the scroll to row area
+                // we need to prevent table itself to expanding beyond available position
+                min-width: 0;
+            }
         }
     }
 
-    &-content {
-        overflow-x: auto;
-    }
-
-    &-grid-head {
-        display: contents;
-    }
-
-    &-grid-body {
-        display: contents;
-    }
-
     &.widget-datagrid-selection-method-click {
         .tr.tr-selected .td {
             background-color: $grid-selected-row-background;
@@ -520,10 +513,30 @@ $root: ".widget-datagrid";
     margin: 0 auto;
 }
 
-.infinite-loading.widget-datagrid-grid-body {
-    // when virtual scroll is enabled we make area that holds rows scrollable
-    // (while the area that holds column headers still stays in place)
-    overflow-y: auto;
+.infinite-loading {
+    .widget-datagrid-grid-head {
+        width: calc(var(--mx-grid-width) - var(--mx-grid-scrollbar-size));
+        overflow-x: hidden;
+    }
+    .widget-datagrid-grid-head[data-scrolled-y="true"] {
+        box-shadow: 0 5px 5px -5px gray;
+    }
+
+    .widget-datagrid-grid-body {
+        width: var(--mx-grid-width);
+        overflow-y: auto;
+        max-height: var(--mx-grid-body-height);
+    }
+
+    .widget-datagrid-grid-head[data-scrolled-x="true"]:after {
+        content: "";
+        position: absolute;
+        left: 0px;
+        width: 10px;
+        box-shadow: inset 5px 0 5px -5px gray;
+        top: 0;
+        bottom: 0;
+    }
 }
 
 .widget-datagrid-grid-head,
diff --git a/packages/pluggableWidgets/datagrid-web/CHANGELOG.md b/packages/pluggableWidgets/datagrid-web/CHANGELOG.md
index b9bea86823..074d8e6e66 100644
--- a/packages/pluggableWidgets/datagrid-web/CHANGELOG.md
+++ b/packages/pluggableWidgets/datagrid-web/CHANGELOG.md
@@ -6,6 +6,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ## [Unreleased]
 
+### Changed
+
+- We improved virtual scrolling behavior when horizontal scrolling is present due to grid size.
+
 ### Added
 
 - We fixed an issue where missing consistency checks for the captions were causing runtime errors instead of in Studio Pro
diff --git a/packages/pluggableWidgets/datagrid-web/src/components/Grid.tsx b/packages/pluggableWidgets/datagrid-web/src/components/Grid.tsx
index 4a4e61d9ec..cbdad7495e 100644
--- a/packages/pluggableWidgets/datagrid-web/src/components/Grid.tsx
+++ b/packages/pluggableWidgets/datagrid-web/src/components/Grid.tsx
@@ -1,17 +1,36 @@
 import classNames from "classnames";
-import { JSX, ReactElement } from "react";
+import { JSX, ReactElement, RefObject } from "react";
 
 type P = Omit<JSX.IntrinsicElements["div"], "role" | "ref">;
 
 export interface GridProps extends P {
     className?: string;
+    isInfinite: boolean;
+    containerRef: RefObject<HTMLDivElement | null>;
+    bodyHeight?: string;
+    gridWidth?: string;
+    scrollBarSize?: string;
 }
 
 export function Grid(props: GridProps): ReactElement {
-    const { className, style, children, ...rest } = props;
+    const { className, style, children, isInfinite, bodyHeight, gridWidth, containerRef, scrollBarSize, ...rest } =
+        props;
 
     return (
-        <div className={classNames("widget-datagrid-grid table", className)} role="grid" style={style} {...rest}>
+        <div
+            className={classNames("widget-datagrid-grid table", { "infinite-loading": isInfinite }, className)}
+            role="grid"
+            style={{
+                ...style,
+                ...({
+                    "--mx-grid-width": gridWidth,
+                    "--mx-grid-body-height": bodyHeight,
+                    "--mx-grid-scrollbar-size": scrollBarSize
+                } as any)
+            }}
+            ref={containerRef}
+            {...rest}
+        >
             {children}
         </div>
     );
diff --git a/packages/pluggableWidgets/datagrid-web/src/components/GridBody.tsx b/packages/pluggableWidgets/datagrid-web/src/components/GridBody.tsx
index b9c3e76bb1..4cd31d2537 100644
--- a/packages/pluggableWidgets/datagrid-web/src/components/GridBody.tsx
+++ b/packages/pluggableWidgets/datagrid-web/src/components/GridBody.tsx
@@ -1,9 +1,8 @@
 import classNames from "classnames";
-import { Fragment, ReactElement, ReactNode } from "react";
-import { LoadingTypeEnum, PaginationEnum } from "../../typings/DatagridProps";
+import { Fragment, ReactElement, ReactNode, RefObject } from "react";
+import { LoadingTypeEnum } from "../../typings/DatagridProps";
 import { SpinnerLoader } from "./loader/SpinnerLoader";
 import { RowSkeletonLoader } from "./loader/RowSkeletonLoader";
-import { useInfiniteControl } from "@mendix/widget-plugin-grid/components/InfiniteBody";
 
 interface Props {
     className?: string;
@@ -15,20 +14,12 @@ interface Props {
     columnsSize: number;
     rowsSize: number;
     pageSize: number;
-    pagination: PaginationEnum;
-    hasMoreItems: boolean;
-    setPage?: (update: (page: number) => number) => void;
+    trackScrolling?: (e: any) => void;
+    bodyRef: RefObject<HTMLDivElement | null>;
 }
 
 export function GridBody(props: Props): ReactElement {
-    const { children, pagination, hasMoreItems, setPage } = props;
-
-    const isInfinite = pagination === "virtualScrolling";
-    const [trackScrolling, bodySize, containerRef] = useInfiniteControl({
-        hasMoreItems,
-        isInfinite,
-        setPage
-    });
+    const { children, bodyRef, trackScrolling } = props;
 
     const content = (): ReactElement => {
         if (props.isFirstLoad) {
@@ -44,15 +35,10 @@ export function GridBody(props: Props): ReactElement {
 
     return (
         <div
-            className={classNames(
-                "widget-datagrid-grid-body table-content",
-                { "infinite-loading": isInfinite },
-                props.className
-            )}
-            style={isInfinite && bodySize > 0 ? { maxHeight: `${bodySize}px` } : {}}
+            className={classNames("widget-datagrid-grid-body table-content", props.className)}
             role="rowgroup"
-            ref={containerRef}
-            onScroll={isInfinite ? trackScrolling : undefined}
+            ref={bodyRef}
+            onScroll={trackScrolling}
         >
             {content()}
         </div>
diff --git a/packages/pluggableWidgets/datagrid-web/src/components/GridHeader.tsx b/packages/pluggableWidgets/datagrid-web/src/components/GridHeader.tsx
index 5ef8785352..9565a39b59 100644
--- a/packages/pluggableWidgets/datagrid-web/src/components/GridHeader.tsx
+++ b/packages/pluggableWidgets/datagrid-web/src/components/GridHeader.tsx
@@ -1,4 +1,4 @@
-import { ReactElement, ReactNode, useCallback, useState } from "react";
+import { ReactElement, ReactNode, RefObject, useCallback, useState } from "react";
 import { ColumnId, GridColumn } from "../typings/GridColumn";
 import { CheckboxColumnHeader } from "./CheckboxColumnHeader";
 import { ColumnResizer } from "./ColumnResizer";
@@ -21,6 +21,7 @@ type GridHeaderProps = {
     id: string;
     isLoading: boolean;
     preview?: boolean;
+    headerRef: RefObject<HTMLDivElement | null>;
 };
 
 export function GridHeader({
@@ -37,7 +38,8 @@ export function GridHeader({
     headerWrapperRenderer,
     id,
     isLoading,
-    preview
+    preview,
+    headerRef
 }: GridHeaderProps): ReactElement {
     const [dragOver, setDragOver] = useState<[ColumnId, "before" | "after"] | undefined>(undefined);
     const [isDragging, setIsDragging] = useState<[ColumnId | undefined, ColumnId, ColumnId | undefined] | undefined>();
@@ -56,7 +58,7 @@ export function GridHeader({
     }
 
     return (
-        <div className="widget-datagrid-grid-head" role="rowgroup">
+        <div className="widget-datagrid-grid-head" role="rowgroup" ref={headerRef}>
             <div key="headers_row" className="tr" role="row">
                 <CheckboxColumnHeader key="headers_column_select_all" />
                 {columns.map((column, index) =>
diff --git a/packages/pluggableWidgets/datagrid-web/src/components/Widget.tsx b/packages/pluggableWidgets/datagrid-web/src/components/Widget.tsx
index 70b7ae1aed..d4e55fed24 100644
--- a/packages/pluggableWidgets/datagrid-web/src/components/Widget.tsx
+++ b/packages/pluggableWidgets/datagrid-web/src/components/Widget.tsx
@@ -25,6 +25,7 @@ import { WidgetFooter } from "./WidgetFooter";
 import { WidgetHeader } from "./WidgetHeader";
 import { WidgetRoot } from "./WidgetRoot";
 import { WidgetTopBar } from "./WidgetTopBar";
+import { useInfiniteControl } from "@mendix/widget-plugin-grid/components/InfiniteBody";
 
 export interface WidgetProps<C extends GridColumn, T extends ObjectItem = ObjectItem> {
     CellComponent: CellComponent<C>;
@@ -157,6 +158,14 @@ const Main = observer(<C extends GridColumn>(props: WidgetProps<C>): ReactElemen
     });
 
     const selectionEnabled = selectActionHelper.selectionType !== "None";
+    const isInfinite = paginationType === "virtualScrolling";
+
+    const [trackBodyScrolling, bodyHeight, gridWidth, scrollBarSize, gridBodyRef, gridContainerRef, gridHeaderRef] =
+        useInfiniteControl({
+            setPage,
+            isInfinite,
+            hasMoreItems
+        });
 
     return (
         <Fragment>
@@ -166,6 +175,11 @@ const Main = observer(<C extends GridColumn>(props: WidgetProps<C>): ReactElemen
                 <Grid
                     aria-multiselectable={selectionEnabled ? selectActionHelper.selectionType === "Multi" : undefined}
                     style={cssGridStyles}
+                    containerRef={gridContainerRef}
+                    isInfinite={isInfinite}
+                    bodyHeight={bodyHeight}
+                    gridWidth={gridWidth}
+                    scrollBarSize={scrollBarSize}
                 >
                     <GridHeader
                         availableColumns={props.availableColumns}
@@ -182,6 +196,7 @@ const Main = observer(<C extends GridColumn>(props: WidgetProps<C>): ReactElemen
                         id={props.id}
                         isLoading={props.columnsLoading}
                         preview={props.preview}
+                        headerRef={gridHeaderRef}
                     />
                     {showRefreshIndicator ? <RefreshIndicator /> : null}
                     <GridBody
@@ -192,9 +207,8 @@ const Main = observer(<C extends GridColumn>(props: WidgetProps<C>): ReactElemen
                         columnsSize={visibleColumns.length}
                         rowsSize={rows.length}
                         pageSize={pageSize}
-                        pagination={props.paginationType}
-                        hasMoreItems={hasMoreItems}
-                        setPage={setPage}
+                        trackScrolling={trackBodyScrolling}
+                        bodyRef={gridBodyRef}
                     >
                         <RowsRenderer
                             preview={props.preview ?? false}
diff --git a/packages/shared/widget-plugin-grid/src/components/InfiniteBody.tsx b/packages/shared/widget-plugin-grid/src/components/InfiniteBody.tsx
index ffbf811670..788c79b827 100644
--- a/packages/shared/widget-plugin-grid/src/components/InfiniteBody.tsx
+++ b/packages/shared/widget-plugin-grid/src/components/InfiniteBody.tsx
@@ -1,36 +1,45 @@
-import {
-    CSSProperties,
-    PropsWithChildren,
-    ReactElement,
-    RefObject,
-    useCallback,
-    useLayoutEffect,
-    useRef,
-    useState
-} from "react";
-import classNames from "classnames";
+import { PropsWithChildren, RefObject, useCallback, useLayoutEffect, useRef, useState } from "react";
 import { useOnScreen } from "@mendix/widget-plugin-hooks/useOnScreen";
 
 export interface InfiniteBodyProps {
-    className?: string;
     hasMoreItems: boolean;
     isInfinite: boolean;
-    role?: string;
     setPage?: (computePage: (prevPage: number) => number) => void;
-    style?: CSSProperties;
 }
 const offsetBottom = 30;
 
 export function useInfiniteControl(
     props: PropsWithChildren<InfiniteBodyProps>
-): [trackScrolling: (e: any) => void, bodySize: number, containerRef: RefObject<HTMLDivElement | null>] {
+): [
+    trackBodyScrolling: ((e: any) => void) | undefined,
+    bodyHeight: string | undefined,
+    gridWidth: string | undefined,
+    scrollBarSize: string | undefined,
+    gridBodyRef: RefObject<HTMLDivElement | null>,
+    gridContainerRef: RefObject<HTMLDivElement | null>,
+    gridHeaderRef: RefObject<HTMLDivElement | null>
+] {
     const { setPage, hasMoreItems, isInfinite } = props;
-    const [bodySize, setBodySize] = useState<number>(0);
-    const containerRef = useRef<HTMLDivElement>(null);
-    const isVisible = useOnScreen(containerRef as RefObject<HTMLElement>);
+    const [gridWidth, setGridWidth] = useState<string | undefined>();
+    const [bodyHeight, setBodyHeight] = useState<string | undefined>();
+    const [scrollBarSize, setScrollBarSize] = useState<string | undefined>();
+    const gridContainerRef = useRef<HTMLDivElement | null>(null);
+    const gridBodyRef = useRef<HTMLDivElement>(null);
+    const gridHeaderRef = useRef<HTMLDivElement | null>(null);
+    const isVisible = useOnScreen(gridBodyRef as RefObject<HTMLElement>);
 
-    const trackScrolling = useCallback(
+    const trackBodyScrolling = useCallback(
         (e: any) => {
+            const head = gridHeaderRef.current;
+            if (head) {
+                head.scrollTo({ left: e.target.scrollLeft });
+                head.dataset.scrolledY = e.target.scrollTop > 0 ? "true" : "false";
+                head.dataset.scrolledX = e.target.scrollLeft > 0 ? "true" : "false";
+            }
+
+            const scrollBarSize = e.target.offsetWidth - e.target.clientWidth;
+            setScrollBarSize(`${scrollBarSize}px`);
+
             /**
              * In Windows OS the result of first expression returns a non integer and result in never loading more, require floor to solve.
              * note: Math floor sometimes result in incorrect integer value,
@@ -48,31 +57,40 @@ export function useInfiniteControl(
         [hasMoreItems, setPage]
     );
 
-    const calculateBodyHeight = useCallback((): void => {
-        if (isVisible && isInfinite && hasMoreItems && bodySize <= 0 && containerRef.current) {
-            setBodySize(containerRef.current.clientHeight - offsetBottom);
+    const lockGridBodyHeight = useCallback((): void => {
+        if (isVisible && isInfinite && hasMoreItems && bodyHeight === undefined && gridBodyRef.current) {
+            setBodyHeight(`${gridBodyRef.current.clientHeight - offsetBottom}px`);
         }
-    }, [isInfinite, hasMoreItems, bodySize, isVisible]);
+    }, [isInfinite, hasMoreItems, bodyHeight, isVisible]);
 
     useLayoutEffect(() => {
-        setTimeout(() => calculateBodyHeight(), 100);
-    }, [calculateBodyHeight]);
+        setTimeout(() => lockGridBodyHeight(), 100);
+    }, [lockGridBodyHeight]);
 
-    return [trackScrolling, bodySize, containerRef];
-}
+    useLayoutEffect(() => {
+        const observeTarget = gridContainerRef.current;
+        if (!isInfinite || !observeTarget) return;
 
-export function InfiniteBody(props: PropsWithChildren<InfiniteBodyProps>): ReactElement {
-    const { className, isInfinite } = props;
-    const [trackScrolling, bodySize, containerRef] = useInfiniteControl(props);
-    return (
-        <div
-            ref={containerRef}
-            className={classNames(className, isInfinite ? "infinite-loading" : "")}
-            onScroll={isInfinite ? trackScrolling : undefined}
-            role={props.role}
-            style={isInfinite && bodySize > 0 ? { ...props.style, maxHeight: bodySize } : props.style}
-        >
-            {props.children}
-        </div>
-    );
+        const resizeObserver = new ResizeObserver(entries => {
+            for (const entry of entries) {
+                setGridWidth(entry.target.clientWidth ? `${entry.target.clientWidth}px` : undefined);
+            }
+        });
+
+        resizeObserver.observe(observeTarget);
+
+        return () => {
+            resizeObserver.unobserve(observeTarget);
+        };
+    }, [isInfinite]);
+
+    return [
+        isInfinite ? trackBodyScrolling : undefined,
+        bodyHeight,
+        gridWidth,
+        scrollBarSize,
+        gridBodyRef,
+        gridContainerRef,
+        gridHeaderRef
+    ];
 }