I’ve been working on gnome-shell’s IM notifications recently. The idea is to unify all notifications about a contact into the same bubble.
If you’re chatting in gnome-shell’s embedded chat and then the contact calls you, the “answer” and “reject” buttons gets into your chat instead of popping a new notification.
Then while the call is connected, the notification stay persistent and have a nice phone icon with call duration timer
What’s great with that design, is that if someone is calling you, there is a chat available right away to answer “sorry I’m busy, calling you later” and the reject the call.
Patches are attached on bug #656028