ADR-0074: A bounded buffer picker replaces the Tabs menu

• Status: Accepted; generalised by ADR-0092
• Date: 2026-09-08
• Deciders: jka
• Decision: D74

Context

Two gaps had the same shape. Compare could only diff the active buffer against a file on disk, while the more common need was comparing against another open tab. And the Tabs menu (ADR-0057) listed every open buffer: it had no size limit, so it could exceed the screen height on X11 (ADR-0064), and it showed only file names, so two tabs with the same name were indistinguishable.

Decision

Both needs use one modal picker dialog: a themed window with a list and a scrollbar that hides when not needed; double-click or Return chooses; Escape cancels. Each row shows the tab name, the unsaved marker, and the parent directory as a hint. The row list is built by a separate procedure so it can be tested without the dialog.

• The Compare menu leads with Compare With Another Tab…, comparing live buffer text on both sides, followed by Compare With A File… and Close Compare.
• The Tabs menu is removed. View ▸ Switch to Tab… opens the same picker and activates the chosen buffer.

Consequences

• No data-driven menu with unbounded length remains except the Theme menu, which followed in ADR-0092 using the same dialog.
• Same-named tabs can be told apart.
• Switch to Tab… has no keyboard shortcut yet.