Checkbox

This entry shows the current shadcn checkbox implementation in Proto UI.

Base Checkbox owns the protocol: controlled and uncontrolled checked and indeterminate, activation from pointer and Space, the effective disabled state, focus, and the checkbox role with its mixed accessible state. Root and Indicator are the whole anatomy, and the shadcn layer adds presentation only — the box, its fill, the focus ring, and the disabled treatment.

The Indicator is derived. It reads checked and indeterminate from the nearest Base Checkbox, picks the tick or the dash, and owns no value, focus, or event of its own. Mixed reads before checked, so a checkbox that is both never paints a tick.