perf: measure sidebar row geometry once before sorting delete anchors

src/renderer/src/components/sidebar/worktree-context-menu-policy.ts

@@ -171,9 +171,10 @@ export function preserveDeleteSiblingPosition(scope: HTMLElement | null): () =>
   if (!(sidebar instanceof HTMLElement) || !(row instanceof HTMLElement)) {
     return () => {}
   }
-  const rows = Array.from(
-    sidebar.querySelectorAll<HTMLElement>('[data-worktree-virtual-row]')
-  ).sort((a, b) => a.getBoundingClientRect().top - b.getBoundingClientRect().top)
+  const rows = Array.from(sidebar.querySelectorAll<HTMLElement>('[data-worktree-virtual-row]'))
+    .map((element) => ({ element, top: element.getBoundingClientRect().top }))
+    .sort((a, b) => a.top - b.top)
+    .map(({ element }) => element)
   const rowIndex = rows.indexOf(row)
   const anchorRow = rows[rowIndex + 1] ?? rows[rowIndex - 1] ?? null
   const anchorKey = anchorRow?.getAttribute('data-worktree-virtual-row-key')

src/renderer/src/components/sidebar/worktree-delete-position-scaling.test.ts

@@ -0,0 +1,22 @@
+// @vitest-environment happy-dom
+import { expect, it } from 'vitest'
+import { preserveDeleteSiblingPosition } from './worktree-context-menu-policy'
+
+it('measures each mounted sidebar row once when choosing a delete-position anchor', () => {
+  const sidebar = document.createElement('div')
+  sidebar.setAttribute('data-worktree-sidebar', '')
+  let measurements = 0
+  const rows = Array.from({ length: 200 }, (_, index) => {
+    const row = document.createElement('div')
+    row.setAttribute('data-worktree-virtual-row', '')
+    row.setAttribute('data-worktree-virtual-row-key', String(index))
+    row.getBoundingClientRect = () => {
+      measurements += 1
+      return { top: (index * 73) % 200 } as DOMRect
+    }
+    sidebar.append(row)
+    return row
+  })
+  expect(typeof preserveDeleteSiblingPosition(rows[100])).toBe('function')
+  expect(measurements).toBeLessThanOrEqual(201)
+})