While none of the client's windows has the focus, a poke or a private
message shows a desktop notification, which the desktop's notification
centre keeps. A private conversation keeps one notification, updated as
messages come; clicking it brings the window forward with that chat open,
and they all go once a window of the client is in front again.
On Linux they go to the freedesktop.org notification service, spoken to
over the session bus by a small D-Bus client of our own on Java's Unix
sockets, so no library or native code is involved; Plasma also takes a
reply typed into the notification. Elsewhere they are AWT tray messages,
which Windows and macOS put in their notification centres. The options
can turn them off.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>