ADR-0064: Menus are kept within screen height by grouping

Status: Accepted
Date: 2026-09-04
Deciders: jka
Decision: D64

Context

On X11, a Tk menu posted taller than the screen space below it unposts when the pointer hovers an item part-way down. The View menu had grown to about 30 rows and triggered this.

Decision

Menus are kept short enough to fit, rather than fixing Tk's menu internals (see ADR-0059). Less frequently used View items were grouped into cascades: Dock Side, Font & Zoom, and Editor Layout. Frequently toggled display options and the pane toggles stay at the top level. The View menu went from about 30 rows to about 18.

A test asserts that the View menu stays small and that the cascades exist.

Consequences

Standing rule: a rio menu stays within screen height by grouping.
Data-driven menus with no upper bound are not acceptable. The Tabs menu (ADR-0074) and the Theme menu (ADR-0092) were later replaced with bounded dialogs for this reason.
The underlying X11 behaviour is recorded in CAVEATS.md.