fix(grid): improve transposed selection and navigation

apps/desktop/src/lib/__tests__/dataGrid/dataGridTranspose.spec.ts

@@ -1,5 +1,16 @@
 import { describe, expect, it } from "vitest";
-import { averageTransposeRecordWidth, calculateTransposeRecordWidth, defaultTransposeRecordWidth, minTransposeFieldWidth, shouldAutoTransposeSingleRow, transposeFieldWidth, transposeRecordWidthsForDensity, visibleTransposeRecordWindow } from "@/lib/dataGrid/dataGridTranspose";
+import {
+  averageTransposeRecordWidth,
+  calculateTransposeRecordWidth,
+  defaultTransposeRecordWidth,
+  minTransposeFieldWidth,
+  shouldAutoTransposeSingleRow,
+  transposeAnchorRowIndex,
+  transposeFieldWidth,
+  transposeScrollLeftForRecord,
+  transposeRecordWidthsForDensity,
+  visibleTransposeRecordWindow,
+} from "@/lib/dataGrid/dataGridTranspose";
 
 describe("single-row automatic transpose", () => {
   it("only opens for enabled multi-column results that are not preserving a manual transpose", () => {
@@ -12,6 +23,21 @@ describe("single-row automatic transpose", () => {
   });
 });
 
+describe("transpose row anchor", () => {
+  it("keeps the requested row when multiple rows or cells are selected", () => {
+    const rowIds = [1, 2, 3, 4];
+
+    expect(
+      transposeAnchorRowIndex({
+        requestedRowIndex: 3,
+        rowIds,
+        selectedRowIds: new Set([1, 4]),
+        selectedRange: { startRow: 0, endRow: 3, startCol: 0, endCol: 1 },
+      }),
+    ).toBe(3);
+  });
+});
+
 describe("dataGridTranspose density widths", () => {
   it("uses the shared density preset for record and field widths", () => {
     const values = ["x".repeat(40)];
@@ -78,3 +104,46 @@ describe("dataGridTranspose density widths", () => {
     expect(averageTransposeRecordWidth([], "compact")).toBe(defaultTransposeRecordWidth("compact"));
   });
 });
+
+describe("transpose record scrolling", () => {
+  it("uses the scroll position after the sticky field for virtualization", () => {
+    expect(
+      visibleTransposeRecordWindow({
+        totalRecords: 3,
+        scrollLeft: 500,
+        viewportWidth: 300,
+        pinnedWidth: 100,
+        recordWidth: 230,
+        recordOffsets: [0, 500, 596, 692],
+        overscan: 0,
+      }),
+    ).toEqual({ start: 1, end: 3, beforeWidth: 500, afterWidth: 0 });
+  });
+
+  it("uses actual record widths and nearest scrolling", () => {
+    const recordOffsets = [0, 500, 596, 692];
+
+    expect(
+      transposeScrollLeftForRecord({
+        recordIndex: 2,
+        totalRecords: 3,
+        viewportWidth: 300,
+        pinnedWidth: 100,
+        recordWidth: 230,
+        recordOffsets,
+        currentScrollLeft: 0,
+      }),
+    ).toBe(492);
+    expect(
+      transposeScrollLeftForRecord({
+        recordIndex: 1,
+        totalRecords: 3,
+        viewportWidth: 300,
+        pinnedWidth: 100,
+        recordWidth: 230,
+        recordOffsets,
+        currentScrollLeft: 450,
+      }),
+    ).toBe(450);
+  });
+});