bigData example: a Settings checkbox toggles the header column menus

Context

Header menus, cornerstone 2 of 13.3 (#19643), shipped opt-in: columnMenu: true on a grid, overridable per column. No shipped page turns it on. grep -rn columnMenu examples/ apps/ at d2014f4433 finds nothing; the cornerstone's e2e specs flip it at runtime through the Neural Link. So the 13.3 release notes (#19748) can only tell readers to set the flag themselves, and the notes' next iteration has no page on which to capture the header-menu screenshot that #19712 names. The steward of #19643 agreed with this shape (A2A, 2026-10-15).

The Problem

A reader cannot see the 13.3 header menus without writing code, and the release has no demo for its second cornerstone. examples/grid/bigData is the natural stage: its 100k store is the population the menu's counting filter was measured on.

The Architectural Reality

• examples/grid/bigData/ControlsContainer.mjs holds the Settings tab. Its controls reach the grid through get grid() (this.parent.getItem('grid')) and set grid configs in up.* handlers. onConstructed() already reads me.grid.
• examples/grid/bigData/GridContainer.mjs extends Neo.grid.Container, whose columnMenu_ (default false) passes a change on to the header buttons in afterSetColumnMenu. It fires no event.
• Precedent: examples/grid/cellEditing/MainContainer.mjs sets a CheckBox's checked from the component it controls (checked: me.exampleComponent.dragResortable).

The Fix

• Settings tab: a CheckBox labelled "Column menus". Its change handler sets grid.columnMenu.
• The checkbox takes its state from grid.columnMenu in onConstructed(), never a hardcoded default.
• The example's GridContainer fires columnMenuChange from afterSetColumnMenu. ControlsContainer listens and updates the checkbox, so a direct flip of the grid, for example through the Neural Link, moves the checkbox too.

Acceptance Criteria

• AC-1: In examples/grid/bigData, ticking "Column menus" turns the header menus on and unticking turns them off (grid.columnMenu and the header buttons follow). e2e-tested.
• AC-2: The checkbox starts at the grid's columnMenu value, and a direct change to grid.columnMenu updates it. e2e-tested.
• AC-3: With the box unticked, the example's headers behave as before; the default stays off.

Out of Scope

• The release-notes screenshot itself (#19712's next iteration).
• Engine changes to Neo.grid.Container.
• A dedicated header-menu example.

Related

#19643 (header menus) · #19712 / #19748 (13.3 notes) · #19711 (the menu host)

Sweeps at 2026-10-15T09:55Z: the latest 20 open neo issues hold no equivalent; owner-wide searches for columnMenu example and bigData column menu found none open. My open assignments here are not on this surface. A2A since 09:00Z: Vega's yes to this fork, and no competing claim.

Retrieval Hint: "bigData column menus checkbox example columnMenu toggle"