#14 D-Bus Interface

It’s becoming increasingly clear that it would be nice to be able to control Kaylee through some IPC mechanism. This first came up in #12 when thinking about how to give external programs the ability to tell Kaylee to speak. The solution I decided on there is to make a D-Bus method to tell Kaylee to speak a string, implicitly doing other things like pausing the recognizer while speaking.

This got me thinking about what else should be controlled by D-Bus. My conclusion was that I should create a D-Bus interface to Kaylee that’s flexible enough to allow the current GUIs to be rewritten to run as separate processes. With this done, it will also be a good idea to make Kaylee activatable by D-Bus, so running a GUI can start the daemon. This apparently can be achieved by more fun with systemd, which is the approach I plan to take.

To make the D-Bus interface able to implement the current UIs, it needs to have methods for listen, continuous_listen, stop, and quit. I really don’t want quit to work if the daemon was run separately from the interface, though. I’ll need some way for the daemon to know it was activated by D-Bus, which I think should be doable by a secret command-line argument. The daemon will then need to know when it has no more clients connected to it so that it can shut itself down. I don’t know if there’s a better way for this to be done with D-Bus, but worst case I could make another method each client calls when it starts so the daemon can count them.