fix: grid does not render items when initialTopMostItemIndex is set t…

…o 1 or more (#1162)
petyosi · Nov 21, 2024 · 483654f · 483654f
1 parent 3405b64
commit 483654f
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Showing 2 changed files with 19 additions and 1 deletion.
diff --git a/src/gridSystem.ts b/src/gridSystem.ts
@@ -232,7 +232,7 @@ export const gridSystem = /*#__PURE__*/ u.system(
 
             if (itemWidth === 0) {
               const startIndex = getInitialTopMostItemIndexNumber(initialTopMostItemIndex, totalCount)
-              const endIndex = Math.max(startIndex + initialItemCount - 1, 0)
+              const endIndex = startIndex + Math.max(initialItemCount - 1, 0)
               return buildProbeGridState(buildItems(startIndex, endIndex, data))
             }
 

diff --git a/test/Grid.test.tsx b/test/Grid.test.tsx
@@ -43,6 +43,24 @@ describe('Grid', () => {
     expect(listParent.textContent).toBe('Item 0')
   })
 
+  it('renders a probe item initially with the initialTopMostItemIndex', () => {
+    act(() => {
+      ReactDOM.createRoot(container).render(<VirtuosoGrid totalCount={20000} initialTopMostItemIndex={10} />)
+    })
+
+    const scroller = container.firstElementChild as any
+    const viewport = scroller.firstElementChild
+    const listParent = viewport.firstElementChild
+
+    act(() => {
+      scroller.triggerScroll({ scrollTop: 0, scrollHeight: 700, viewportHeight: 200 })
+      viewport.triggerResize({ getBoundingClientRect: () => ({ height: 700 }) })
+    })
+
+    expect(listParent.children).toHaveLength(1)
+    expect(listParent.textContent).toBe('Item 10')
+  })
+
   describe('data list', () => {
     let scroller: any
     let viewport: any