From 99c4d846013d6428410aadb9e7e874159b15f5b6 Mon Sep 17 00:00:00 2001
From: Markus Obelitz <mo@abtion.com>
Date: Sat, 3 Oct 2026 23:12:48 +0200
Subject: [PATCH] fix(layout): place the next grid row below the row's tallest
 item

A stale minHeight left over from previous data could exclude the row's real
tallest item from the tallest check. The uneven-row branch then reset the
min heights but returned the shorter item, so the next row started too high
and overlapped the taller items, and nothing corrected it afterwards.

Fixes #2519
---
 src/__tests__/GridLayoutManager.test.ts       | 30 +++++++++++++++++++
 .../layout-managers/GridLayoutManager.ts      | 12 ++++++++
 2 files changed, 42 insertions(+)

diff --git a/src/__tests__/GridLayoutManager.test.ts b/src/__tests__/GridLayoutManager.test.ts
index 15daa1d4b..715639c6e 100644
--- a/src/__tests__/GridLayoutManager.test.ts
+++ b/src/__tests__/GridLayoutManager.test.ts
@@ -1,4 +1,6 @@
 import {
+  createLayoutManager,
+  createMockLayoutInfo,
   createPopulatedLayoutManager,
   getAllLayouts,
   LayoutManagerType,
@@ -109,5 +111,33 @@ describe("GridLayoutManager", () => {
       expect(updatedLayouts[0]).toEqual(initialLayouts[0]);
       expect(updatedLayouts[3].y).toBe(initialLayouts[0].height);
     });
+
+    it("should place the next row below the tallest item after data changes", () => {
+      const manager = createLayoutManager(LayoutManagerType.GRID, {
+        ...defaultParams,
+        windowSize: { width: 300, height: 900 },
+        maxColumns: 3,
+      });
+      const measure = (heights: number[]) =>
+        manager.modifyLayout(
+          heights.map((height, index) =>
+            createMockLayoutInfo(index, 100, height)
+          ),
+          heights.length
+        );
+
+      // The middle item is tallest, so its neighbours get its height as minHeight.
+      measure([408, 437, 408, 400, 400, 400]);
+      // New data at the same indices: tall, short, tall. The outer items now
+      // measure exactly their stale minHeight.
+      measure([437, 408, 437, 400, 400, 400]);
+
+      const layouts = getAllLayouts(manager);
+      expect(layouts[3].y).toBe(437);
+
+      // Measuring the same sizes again keeps it there.
+      measure([437, 408, 437, 400, 400, 400]);
+      expect(getAllLayouts(manager)[3].y).toBe(437);
+    });
   });
 });
diff --git a/src/recyclerview/layout-managers/GridLayoutManager.ts b/src/recyclerview/layout-managers/GridLayoutManager.ts
index c9517568c..31fa26280 100644
--- a/src/recyclerview/layout-managers/GridLayoutManager.ts
+++ b/src/recyclerview/layout-managers/GridLayoutManager.ts
@@ -183,6 +183,18 @@ export class RVGridLayoutManagerImpl extends RVLayoutManager {
       if (maxHeight - tallestItem.height > 1) {
         targetHeight = 0;
         this.requiresRepaint = true;
+        // A stale minHeight (e.g. after data changed) can hide the row's real
+        // tallest item from the check above. The next row has to start below
+        // it, or it overlaps the taller items in this row.
+        for (
+          let j = startIndex;
+          j <= endIndex && j < this.layouts.length;
+          j++
+        ) {
+          if (this.layouts[j].height > tallestItem.height) {
+            tallestItem = this.layouts[j];
+          }
+        }
       }
       i = startIndex;
       while (i <= endIndex) {