Keep a Toast inside its host: Toast.MaxW, and export WrapText

[tannevaled]

A Toast sizes itself to its widest line with no upper bound. A host that docks one to a centre anchor then paints a pill wider than the view, so both ends are cut and the reader gets the middle of a sentence — which is worse than a truncated message, because it does not look truncated.

Measured, not supposed

In go-xrkit/desk, on a 1920-wide view at the size it draws its notices (30 px ink, 43 px body):

message	pill	verdict
screen 3 is back	329 px	fits
the camera was refused; it is turned on again in System Settings > Privacy & Security > Camera	2373 px	⛔ 1.2× the width
a longer refusal	4975 px	⛔ 2.6× the width

The middle one already ships. Anybody whose camera has been denied has been reading the middle of that sentence.

What changed

• Toast.MaxW — when positive, the widest the pill may be drawn; Text is wrapped across as many rows as it needs. The zero value keeps the old behaviour exactly: no wrapping, no measuring, one line. Lines still wins, since a caller supplying its own rows has already decided where they break.
• The wrap is memoised, because lines() is asked three times a frame (sizing, height, drawing) and wrapping costs a measure per word. The key is (text, width, glyph height) and not the Font itself — comparing an interface can panic on an uncomparable dynamic type; the documented consequence is a mis-wrap between two fonts of identical height, never a crash, and it corrects itself on any change.
• WrapText exports the routine the card widgets already lay their bodies out with. It was private, so a widget outside cardframe.go had to write its own — and wrap to different rules than the card beside it.
• MaxW is set-once layout config, so it joins the Toast entry in the MVVM gate's allow-list alongside Lines, Icon and Actions.

The tests are proved by sabotage

Making wrapWidthFor return 0 makes them fail, naming the overflow (pill 584px, want at most 300px). The first sabotage attempt silently did not apply and the suite stayed green — the file was checked for the change before anything was concluded from it.

🤖 Generated with Claude Code