Add support for announcements
ATK handles text changes in a widget that's currently in focus brilliantly, but sometimes an application needs to announce that an unfocused widget has changed its text as well.
Mudlet, for example, has two widgets - an input line and a text buffer. The users primary keyboard focus is on the input line, but when unsolicited text arrives in the text buffer, it must be read out.
In the web world, this is made possible using live regions. In the desktop world, macOS exponses NSAccessibilityAnnouncementRequestedNotification and Android has a TYPE_ANNOUNCEMENT event type.
ATK's object model (as exposed by AT-SPI2) lacks such an event, and this really hampers accessibility on Linux. Gecko has had to resort to a hack to make live regions work, Chromium didn't implement live regions on Linux at all, Flutter didn't implement support for announcements (while they did for macOS). You get the idea. Orca has to resort to heuristics and workarounds to support this kind of announcement because of the base protocol lacking.
It would be fantastic to have support for an explicit announcement/alert type of event in the base protocol to enable this usecase!