[EdLUG] Notifications and ubuntu 19.10

[Thomas Kluyver]

On Mon, 12 Oct 2020, at 15:48, Andrew Smith wrote:
> Would like to learn how notifications actually work.

Assuming you mean desktop notifications - the little bubbles that appear to tell you about things like new updates or chat messages - I know a bit about this.

All* modern desktop Linux systems have D-Bus, a messaging system to let local applications communicate. Desktop notifications are one of the most visible things using this. Your desktop environment (Gnome/KDE/etc.) registers itself on D-Bus as the notification server when it starts. Applications send it messages with the details of a notification to show (e.g. text and an optional icon), and it's up to the desktop how to display it. There's a specification for this:

https://specifications.freedesktop.org/notification-spec/notification-spec-latest.html

Of course, some applications ignore this and display their own notifications directly, e.g. making a new window with no title bar. This tends to look a bit out of place. E.g. Thunderbird did this for a long time; I don't know if it's changed now.

(* Probably not actually *all*, because there are so many ways to set up desktop Linux. But if you're running any mainstream distro from the last 10 years or so, you've almost certainly got D-Bus.)

Thomas
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