An installed app had no title bar of its own, no way to save attachments
except a zip, and "pop out" stayed inside the page. A new window was a
second copy of the app that had to restore the session itself, and on
start-up that evicts any login made without "Remember me" from the list
every window shares.
- Title bar: `display_override` with `window-controls-overlay`, one
`--titlebar-inset` variable at the page roots and skeletons, and a drag
strip with the window title. 0 without an overlay, so nothing moves.
- Save all to a folder: `showDirectoryPicker`, asking the device policy
before the picker and before each file, with the zip as the fallback.
- Pop-out routes `/popout/message/<id>` and `/popout/compose`, on offer in
an installed app or when the desktop bridge has windows. Hidden in Lite.
- A pop-out borrows the main window's session and never evicts or starts a
token timer. Every renewal now takes a Web Lock, so two windows can't
send the same refresh token, which Stalwart 1.0 may treat as a replay.
- A draft moves to its window under the same id. A closing window hands
unsaved text to the main window to save, since its own request wouldn't
survive the close.
- Read state, drafts, theme and language follow across windows, and
`html[data-desktop]` gates the app-like behaviour in `app/desktop.css`.
- The button and the panel of Calendar, Contacts, Files and Settings
show only when the plugin's shouldShow says yes, so a plugin switched
off for these views (admin, user or no service) leaves no button that
opens an empty panel, and no extra rows in Contacts and Settings.
- Files: while the details are open the panel steps aside there only;
the other views keep it as the user left it. With both stored open the
details fold when the page loads.
- Resizing stops where the view keeps its 480 px, so a drag or the arrow
keys no longer fold the panel away (and the handle keeps the focus).
- Settings and Contacts render the same element with or without the
panel, so a form keeps what was typed when the panel starts docking.
- Contacts on a phone: the panel button sits over an open contact too.
- The panel buttons of the reader and the views have one name, "Plugin
panel", with aria-pressed, and name the plugin's panel shortcut in
their title; the open panels are named landmarks.
The reader tests look the button up by its new name and pressed state
(viewer-toolbar-over-side-panel, reader-plugin-surfaces,
viewer-plugin-panel-width), since "Show/Hide plugin panel" is gone.