Add an "Interface layout" setting at the top of Settings > Layout with two
options, Default and Mountain View. Default is the existing layout and stays
the default, so nothing changes unless a user opts in.
Mountain View rearranges the chrome while keeping the theme's colours, icons
and type:
- desktop: a top bar with a wide search field (filters drop from the field),
an apps grid and the account avatar instead of the left app rail; flat
navigation with Starred under Inbox and the rest behind "More"; a Compose
pill; one list toolbar with select-all, refresh, overflow menu, a 1-N of
total range and the batch actions; rows led by a checkbox and a star; an
icon-only message toolbar with Reply / Reply all / Forward under the
message; compose in a docked window; an account popover with per-account
unread counts; j/k cursor, x to select and g-sequences
- phone: rounded search header, compact rows with the star on the preview
line, and Reply / Reply all / Forward at the end of a message instead of
the bottom action bar
It is one setting (`interfaceLayout`), written to a data attribute on <html>
that keys a block of CSS tokens in globals.css, plus a few components gated
on the flag. The mail layout in force is derived (effectiveMailLayout), so
the user's saved mail layout is never rewritten. The setting is listed in
the admin policy tab, and the new strings are translated in all locales.
Includes unit tests and a Playwright smoke test against a running instance
(scripts/mountain-view-smoke/).
Linus Rath
lucamzanon