path: root/2022/info/dbus-after.md

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<a name="dbus-mainVideo-transcript"></a>
# Transcript

[[!template new="1" text="""Welcome to my EmacsConf 2022 talk, The Wheels on D-Bus.""" start="00:00:00.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""In this talk, we'll cover what D-Bus is,""" start="00:00:04.880" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""why you might want to use it, and how to use it with Emacs.""" start="00:00:07.440" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""D-Bus is fundamentally based on passing messages""" start="00:00:10.760" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""in between processes, using the bus as a mediator.""" start="00:00:13.680" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""On top of this is built an RPC system with method invocation""" start="00:00:17.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""that has argument lists and return values,""" start="00:00:20.600" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""like you might find in any programming language.""" start="00:00:22.800" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""These are commonly used for verb-type actions""" start="00:00:25.480" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""like &quot;restart my computer.&quot;""" start="00:00:27.840" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""You can also associate a collection of attributes""" start="00:00:30.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""with objects on the bus, and these are called properties.""" start="00:00:32.640" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""The properties can be read-only, write-only, or read-write.""" start="00:00:35.840" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Signals are a way of notifying participants on the bus""" start="00:00:39.840" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""of updated state, and are the basis""" start="00:00:43.160" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""for building dynamic user interfaces""" start="00:00:46.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""that react to changes in the system.""" start="00:00:47.800" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""It has a static and strong type system,""" start="00:00:50.480" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""so if you send a message with the wrong type signature,""" start="00:00:52.760" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""it simply gets rejected instead of going through""" start="00:00:55.360" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""to the remote service.""" start="00:00:57.840" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""It also manages service life cycles,""" start="00:00:59.600" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""so you're not running services at all times.""" start="00:01:02.320" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""They can be started and stopped by D-Bus on demand.""" start="00:01:04.400" video="mainVideo-dbus" id="subtitle"]]
[[!template new="1" text="""D-Bus has two major use cases.""" start="00:01:07.880" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""The first is acting as a lower-level substrate""" start="00:01:10.520" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""for higher-level programs,""" start="00:01:13.360" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""like a graphical desktop environment.""" start="00:01:14.680" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""For example, if you want to manage your network connectivity""" start="00:01:16.920" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""from your graphical environment,""" start="00:01:19.600" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""instead of having to build all of that from the ground up,""" start="00:01:21.240" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""you can rely on the D-Bus service to do that""" start="00:01:23.920" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and only build the graphical component of it.""" start="00:01:26.240" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""This gives you consistency between desktop environments""" start="00:01:28.680" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and reduces code duplication.""" start="00:01:31.320" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Another application is automating desktop programs.""" start="00:01:33.800" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""If your program offers a D-Bus service,""" start="00:01:37.320" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""then it can be remote-controlled,""" start="00:01:39.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and if all of your programs offer D-Bus,""" start="00:01:40.960" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""you can control your entire desktop.""" start="00:01:42.760" video="mainVideo-dbus" id="subtitle"]]
[[!template new="1" text="""Let's look at the abstractions that D-Bus provides.""" start="00:01:45.360" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""The top level object is called a bus,""" start="00:01:48.560" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and it's like a partition""" start="00:01:51.240" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""that messages get exchanged inside of.""" start="00:01:52.360" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Messages don't cross buses.""" start="00:01:54.920" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Inside of a bus are services.""" start="00:01:57.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Services are normally identified in reverse FQDN order,""" start="00:01:59.560" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""so org.foobar.FooService.""" start="00:02:03.160" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Each service provides some set of features""" start="00:02:06.160" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""related to a particular area of functionality.""" start="00:02:08.600" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Inside of each service are objects.""" start="00:02:11.760" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Objects use a path notation,""" start="00:02:14.440" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and usually follow the same reverse FQDN format""" start="00:02:16.600" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""as the service identifier.""" start="00:02:19.760" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Each object has one or more interfaces.""" start="00:02:21.960" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""An interface is like a facet that you can use""" start="00:02:24.880" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""to interact with an object,""" start="00:02:27.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and inside of the interface are properties, methods,""" start="00:02:29.480" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and signals, which we covered before.""" start="00:02:32.240" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Properties are attributes that can be read or written.""" start="00:02:34.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Methods are verbs that you can call to invoke an action,""" start="00:02:37.040" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and a signal is something that's used to move state""" start="00:02:40.240" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""in between a service and another participant on the bus.""" start="00:02:43.320" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""There can be any number of interfaces on an object,""" start="00:02:47.240" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""any number of objects in a service,""" start="00:02:49.600" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and any number of services on a bus,""" start="00:02:51.480" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and any number of buses on a system.""" start="00:02:53.440" video="mainVideo-dbus" id="subtitle"]]
[[!template new="1" text="""There are two well-known busses,""" start="00:02:55.360" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and these roughly map to those two use cases""" start="00:03:00.040" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""I mentioned before.""" start="00:03:02.360" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""The system bus is for interfacing with hardware""" start="00:03:03.640" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and operating-system-level concerns""" start="00:03:06.480" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""like disks, networks, and so forth.""" start="00:03:08.440" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""The session bus is tied to a user login,""" start="00:03:11.680" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and is more in the desktop automation use case.""" start="00:03:14.320" video="mainVideo-dbus" id="subtitle"]]
[[!template new="1" text="""There are some common interfaces you'll find""" start="00:03:20.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""if you go exploring D-Bus.""" start="00:03:21.920" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""The Introspectable interface is the basis""" start="00:03:23.960" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""of a lot of the reflection features.""" start="00:03:26.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""It has a single method called introspect""" start="00:03:27.920" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""that returns the XML interface description""" start="00:03:30.120" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""of whatever you call it on.""" start="00:03:32.240" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Peer is used for lower level connectivity,""" start="00:03:33.400" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""for example, pinging a service to see if it's running.""" start="00:03:36.560" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""And the Properties interface is the basis""" start="00:03:39.680" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""of the read-write properties,""" start="00:03:41.760" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""which are secretly method calls under the cover.""" start="00:03:43.120" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Just about every object you interact with on D-Bus""" start="00:03:45.800" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""will support all three of these interfaces.""" start="00:03:48.520" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Additionally, ObjectManager is used for services""" start="00:03:51.400" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""that manage collections of objects.""" start="00:03:54.760" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""For example, the disk service has an object""" start="00:03:56.760" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""for each disk that's attached,""" start="00:03:59.840" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and the object manager allows you""" start="00:04:01.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""to enumerate all of those.""" start="00:04:02.800" video="mainVideo-dbus" id="subtitle"]]
[[!template new="1" text="""Emacs supports D-Bus natively since version 23.1.""" start="00:04:06.240" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""It's a combination of native bindings""" start="00:04:10.360" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""with a C library and dbus.el.""" start="00:04:12.120" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""While there are some ports of D-Bus""" start="00:04:14.640" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""to non-Linux operating systems,""" start="00:04:17.560" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""it's probably only available on Linux""" start="00:04:19.480" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and almost certainly only usable on Linux.""" start="00:04:22.040" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""If you want to interact with D-Bus from Emacs,""" start="00:04:24.440" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""it's fairly straightforward.""" start="00:04:28.920" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""There's a collection of functions like dbus-get-property""" start="00:04:30.080" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""or dbus-call-method, et cetera,""" start="00:04:33.200" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and they almost all take this same set""" start="00:04:35.040" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""of four arguments at the beginning:""" start="00:04:37.640" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""bus, service, path, and interface.""" start="00:04:39.320" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""In this case, it takes a single additional property,""" start="00:04:42.120" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""which is the one to read.""" start="00:04:45.440" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""And what we're calling is the hostname1 service,""" start="00:04:46.600" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""which gives you just a little bit of information""" start="00:04:49.680" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""about the system, like its hostname or its chassis.""" start="00:04:51.520" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""And in this case, you can see I'm running""" start="00:04:54.760" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""this presentation off my laptop.""" start="00:04:56.200" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""The problem with this and what I don't like about it""" start="00:04:57.720" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""is that all of these identifiers are very verbose""" start="00:05:00.960" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and very repetitive.""" start="00:05:04.600" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""And if you end up calling these a lot,""" start="00:05:05.720" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""it gets old really quickly.""" start="00:05:07.680" video="mainVideo-dbus" id="subtitle"]]
[[!template new="1" text="""So I wrote a wrapper called Debase,""" start="00:05:09.320" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""which is convenience on top of the built-in functions.""" start="00:05:13.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Most of the stock functions have Debase versions""" start="00:05:15.840" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""just by replacing &quot;dbus&quot; with &quot;debase&quot;.""" start="00:05:18.840" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""And let's look how that works.""" start="00:05:21.520" video="mainVideo-dbus" id="subtitle"]]
[[!template new="1" text="""The fundamental idea of Debase is that you can bind together""" start="00:05:23.880" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""all of those arguments into a single object""" start="00:05:28.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""that represents the endpoint.""" start="00:05:30.320" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""This is an EIEIO class, and it takes keyword arguments,""" start="00:05:31.560" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""so there's never any chance""" start="00:05:35.600" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""of mixing up which thing is what.""" start="00:05:36.880" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""So this sets the endpoint to that object,""" start="00:05:38.560" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""calls debase-get-property on it,""" start="00:05:41.480" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and you can see it works exactly the same.""" start="00:05:43.120" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""The thing that's really nice about this, though,""" start="00:05:45.040" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""is it knows that so many of these arguments""" start="00:05:47.360" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""are very similar that it can compute most of them""" start="00:05:50.200" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""if you don't provide them all.""" start="00:05:52.920" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""So if you just say service, it will assume""" start="00:05:54.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""that you want the same object that matches""" start="00:05:57.160" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and the same interface that matches,""" start="00:05:59.160" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and it works just the same.""" start="00:06:00.880" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""I find this very, very convenient.""" start="00:06:02.320" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""You can also reuse the object""" start="00:06:04.880" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""instead of having to repeat every argument""" start="00:06:07.240" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""with every function call,""" start="00:06:09.160" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""which is a really great improvement in ergonomics.""" start="00:06:10.400" video="mainVideo-dbus" id="subtitle"]]
[[!template new="1" text="""Because so many objects have multiple interfaces,""" start="00:06:13.440" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""you often find yourself needing to look""" start="00:06:18.120" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""at a different aspect of that object.""" start="00:06:20.320" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""This is supported with the built-in EIEIO clone method,""" start="00:06:22.480" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""which takes an object""" start="00:06:26.600" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and a set of keyword arguments to replace.""" start="00:06:28.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""So in this case, we can see we're calling""" start="00:06:30.440" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""the Properties method,""" start="00:06:32.600" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""but everything else on that endpoint is the same.""" start="00:06:33.480" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""And then we're gonna call the method GetAll""" start="00:06:35.800" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""on that Properties interface,""" start="00:06:38.080" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and it's going to return all the properties""" start="00:06:39.360" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""of the org.freedesktop.hostname1 interface""" start="00:06:41.120" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""inside of that object.""" start="00:06:43.920" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""And if we run that, we can see there's the hostname""" start="00:06:45.200" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and some other information about the laptop""" start="00:06:48.200" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""that I'm running this on.""" start="00:06:50.160" video="mainVideo-dbus" id="subtitle"]]
[[!template new="1" text="""Debase also supports object binding.""" start="00:06:51.080" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""This creates a lexical context in which the Debase object""" start="00:06:54.400" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""is the implicit target of any D-Bus function.""" start="00:06:58.560" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""This is really convenient if you need""" start="00:07:01.120" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""to fetch multiple properties or otherwise interact""" start="00:07:03.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""with the same endpoint in multiple different ways.""" start="00:07:06.480" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""And you can see I'm still on a laptop""" start="00:07:09.320" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and it's still named meson.""" start="00:07:11.360" video="mainVideo-dbus" id="subtitle"]]
[[!template new="1" text="""You can also, if you don't want to use the object,""" start="00:07:12.480" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""you can provide the raw argument list.""" start="00:07:16.320" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Under the covers, this is basically an flet""" start="00:07:18.240" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""where you're currying all of these functions""" start="00:07:20.920" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""so they start with those argument lists.""" start="00:07:23.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""And you can see I'm running on a Linux machine,""" start="00:07:25.440" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""which should not be surprising.""" start="00:07:27.800" video="mainVideo-dbus" id="subtitle"]]
[[!template new="1" text="""Debase also has an experimental code generation feature.""" start="00:07:29.400" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""It outputs EIEIO code with one class per D-Bus interface.""" start="00:07:34.080" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""This includes accessors for all of its properties""" start="00:07:38.360" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""with an in-process cache, so if you read one property,""" start="00:07:41.080" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""you don't have to go back to the bus to read it again.""" start="00:07:44.160" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""It also outputs generic functions and method implementations""" start="00:07:46.400" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""for the D-Bus interface methods.""" start="00:07:50.120" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""It includes name-mangling options,""" start="00:07:52.200" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""so you can control how everything is named.""" start="00:07:54.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""And you can generate the code either""" start="00:07:56.880" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""via introspecting a live system""" start="00:07:58.640" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""or providing an XML interface description,""" start="00:08:00.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""which is handy if you want to use it""" start="00:08:02.640" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""as part of a non-interactive build.""" start="00:08:04.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""I think this has a lot of promise,""" start="00:08:05.920" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""but it doesn't feel quite right yet,""" start="00:08:08.160" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""so any feedback or contributions are very welcome.""" start="00:08:09.680" video="mainVideo-dbus" id="subtitle"]]
[[!template new="1" text="""Let's generate some Elisp code""" start="00:08:14.200" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""for that hostname1 service we were interacting with before.""" start="00:08:16.920" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""debase-gen-class is the generation class,""" start="00:08:19.640" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and it says to create a class that matches this interface,""" start="00:08:23.120" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""named &quot;hostname1&quot;, and then the rest of these arguments""" start="00:08:26.080" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""are the same ones to target the endpoint,""" start="00:08:29.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""just like with debase-object,""" start="00:08:31.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""because it extends debase-object.""" start="00:08:32.920" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""debase-gen-code is a generic function""" start="00:08:34.760" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""that takes any debase-gen class.""" start="00:08:37.680" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""There are different classes for functions,""" start="00:08:40.120" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""properties, et cetera,""" start="00:08:42.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and it creates all of the code for it.""" start="00:08:43.360" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""If we evaluate it, we can see the results""" start="00:08:45.480" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""look about like we would expect:""" start="00:08:48.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""creates a defclass named &quot;hostname1&quot;,""" start="00:08:49.960" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""which extends debase-object,""" start="00:08:52.160" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""has all of the slots and accessors defined,""" start="00:08:53.880" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and then methods that define everything""" start="00:08:56.640" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""that you might want to do with it, including documentation.""" start="00:08:59.320" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""This is based on introspecting a running system,""" start="00:09:01.840" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""but as I mentioned,""" start="00:09:04.760" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""you can provide an XML interface description instead,""" start="00:09:05.480" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""if you like.""" start="00:09:08.040" video="mainVideo-dbus" id="subtitle"]]
[[!template new="1" text="""Debase also comes with &quot;debase-objectmanager&quot;,""" start="00:09:08.680" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""which is convenience for the D-Bus ObjectManager interface.""" start="00:09:12.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""This is used in a lot of places in D-Bus,""" start="00:09:15.400" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""where an object manages other objects.""" start="00:09:18.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""For example, the NetworkManager object""" start="00:09:20.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""manages network hardware objects,""" start="00:09:22.720" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and using the ObjectManager interface,""" start="00:09:25.160" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""you can enumerate all of the network hardware,""" start="00:09:26.880" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and by subscribing to the signals,""" start="00:09:28.880" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""you can be notified when they change.""" start="00:09:31.040" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""&quot;debase-objectmanager&quot; keeps a local cache,""" start="00:09:33.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and will fire a callback on any change.""" start="00:09:36.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""So it's the building block for that dynamic user interface,""" start="00:09:38.120" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""like you would see in a desktop system,""" start="00:09:41.240" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""but inside of Emacs.""" start="00:09:43.120" video="mainVideo-dbus" id="subtitle"]]
[[!template new="1" text="""Let's do some demos.""" start="00:09:44.480" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Discomfort is an interface I wrote for UDisks2,""" start="00:09:47.760" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""which is what manages all of the block device hardware.""" start="00:09:51.040" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""And again, it has that dynamic desktop-like interactivity,""" start="00:09:53.720" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and mostly will just do what you mean.""" start="00:09:57.680" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""This is definitely alpha state.""" start="00:10:00.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""It doesn't have all the features,""" start="00:10:03.520" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""but it's good enough that I use it daily.""" start="00:10:04.840" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""So here's Discomfort,""" start="00:10:06.560" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and you can see it has a list of all your hardware,""" start="00:10:08.880" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""what type it is, and where it's mounted.""" start="00:10:11.680" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""I have a little USB extension cable here,""" start="00:10:13.640" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and I'm gonna plug in a disc,""" start="00:10:16.200" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""just to show you how this works.""" start="00:10:17.680" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""You can see when I plug it in,""" start="00:10:19.320" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""just a moment later,""" start="00:10:21.080" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""it shows up in that list, automatically.""" start="00:10:22.400" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""I don't have to press any key,""" start="00:10:24.440" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""I don't have to refresh it, it's just there.""" start="00:10:25.720" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""If I unplug it, it's gone.""" start="00:10:27.760" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Plug it back in,""" start="00:10:29.520" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and there it is.""" start="00:10:30.720" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""And you can see it's an encrypted volume.""" start="00:10:33.400" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""So in order to do anything with this,""" start="00:10:35.240" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""I'm going to have to supply a password.""" start="00:10:37.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Just pressing Enter goes into the &quot;do what I mean&quot; mode,""" start="00:10:38.680" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and it asks for the password.""" start="00:10:41.760" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""In this case, I've chosen the very secure password""" start="00:10:43.520" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""of &quot;password&quot;.""" start="00:10:46.600" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""I hit Enter, and it unlocks it, and it mounts it,""" start="00:10:47.560" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and it opens &quot;dired&quot; looking at it.""" start="00:10:51.200" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""And here's a little README.""" start="00:10:53.320" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Let's see what it says.""" start="00:10:54.440" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""&quot;Hello, EmacsConf.&quot;""" start="00:10:55.560" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""So that's my demo of discomfort.""" start="00:10:58.560" video="mainVideo-dbus" id="subtitle"]]
[[!template new="1" text="""In addition to acting as a client for D-Bus,""" start="00:11:01.480" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Emacs can also offer services to other D-Bus clients.""" start="00:11:05.840" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""This is a really interesting opportunity""" start="00:11:09.360" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""because it allows many different programs""" start="00:11:11.960" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""to integrate with Emacs""" start="00:11:14.120" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""in ways that were previously very difficult.""" start="00:11:15.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""You can use this as an alternative to Emacs.""" start="00:11:17.680" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""The difference is D-Bus provides a full API,""" start="00:11:20.240" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""so instead of emacsclient being""" start="00:11:23.200" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""a sort of fire-and-forget system,""" start="00:11:25.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""you can actually get results back from the remote operation.""" start="00:11:26.680" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""So here's some code.""" start="00:11:30.120" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Here's a dbus-eval function, which takes a string,""" start="00:11:32.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""reads it, and evaluates it,""" start="00:11:35.680" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and returns whatever that value is.""" start="00:11:37.360" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Then we have a debase-bind block""" start="00:11:39.360" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""that sets up an object on the session bus.""" start="00:11:41.840" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Again, that's my user login bus.""" start="00:11:44.800" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""It offers this D-Bus service Emacs.""" start="00:11:46.840" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""This is a constant inside of the dbus.el package.""" start="00:11:49.560" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""And again, the path is a constant in there.""" start="00:11:53.400" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""And we're gonna create this interface,""" start="00:11:55.440" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""org.gnu.Emacs.Eval, and then register a method called Eval""" start="00:11:57.160" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""that calls that dbus-eval function.""" start="00:12:02.520" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Pretty straightforward, only a handful of lines of code.""" start="00:12:04.760" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""To test this out, we're going to use the dbus-send utility.""" start="00:12:08.120" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""This is a command line program that interacts with D-Bus.""" start="00:12:12.400" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""We're going to tell it to wait for and print the reply,""" start="00:12:15.400" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""that the message should be sent to the session bus,""" start="00:12:18.080" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""that we're going to talk""" start="00:12:21.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""to the org.gnu.Emacs service on that bus,""" start="00:12:22.600" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and the /org/gnu/Emacs object inside that service.""" start="00:12:25.640" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""On that object, we're gonna interact""" start="00:12:30.880" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""with the org.gnu.Emacs.Eval interface""" start="00:12:33.040" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and call its Eval method.""" start="00:12:36.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""We're gonna call that method with a single string argument,""" start="00:12:37.640" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""which is indicated by the string prefix,""" start="00:12:40.640" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and then a form to evaluate.""" start="00:12:42.640" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""I actually have to run this from a shell,""" start="00:12:45.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""because if I try using it in Org, it wedges.""" start="00:12:47.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""org-babel blocks waiting on completion,""" start="00:12:49.400" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""which blocks the D-Bus service from responding.""" start="00:12:51.960" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""I really wish Emacs was multi-threaded.""" start="00:12:54.520" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""But let's try it out.""" start="00:12:57.400" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""So if we run this, we can see that we get a return,""" start="00:12:59.920" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and that's an unsigned integer of 32 bits""" start="00:13:02.720" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""with a value of 3.""" start="00:13:05.240" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""So like I was saying, this is really a two-way API""" start="00:13:06.440" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""where you can communicate back and forth""" start="00:13:09.960" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""between Emacs and another program.""" start="00:13:11.720" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""It's not just fire-and-forget.""" start="00:13:13.400" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""I think that's really cool.""" start="00:13:14.960" video="mainVideo-dbus" id="subtitle"]]
[[!template new="1" text="""Let's try another demo.""" start="00:13:16.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""What about a remote org-capture?""" start="00:13:18.520" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""What if you could trigger an org-capture""" start="00:13:20.600" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""from any program on your desktop?""" start="00:13:23.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""I think that would be pretty cool.""" start="00:13:24.680" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""And we can see, there it is.""" start="00:13:26.240" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""All right, I think I've got that one covered.""" start="00:13:30.240" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""So I do want to say that remote eval is probably a bad idea""" start="00:13:38.920" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""from a security perspective,""" start="00:13:42.320" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""but the point of this is some quick and dirty demonstrations""" start="00:13:43.480" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""of what can happen and to get people's imaginations flowing,""" start="00:13:46.760" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""because I think this is something""" start="00:13:49.800" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""that offers a lot of promise for Emacs.""" start="00:13:51.720" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""I think having a full-blown Emacs desktop environment""" start="00:13:54.080" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""where it can do all the things that a GNOME""" start="00:13:57.800" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""or a KDE environment can do is very exciting.""" start="00:13:59.880" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""And if you want to have a traditional GUI with Emacs""" start="00:14:02.760" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""as a more integrated participant of it,""" start="00:14:06.440" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""its service mechanism offers a lot of ability to do that.""" start="00:14:08.680" video="mainVideo-dbus" id="subtitle"]]
[[!template new="1" text="""In the micro sense, I think there's a lot of improvements""" start="00:14:11.880" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""that can be made to either dbus.el or to dbase.""" start="00:14:16.000" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""The main one is handling of the type system.""" start="00:14:19.280" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Lisp's dynamic type system doesn't mesh particularly well""" start="00:14:21.640" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""with the static strong type system that D-bus offers,""" start="00:14:25.840" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and having some convenience to assist that""" start="00:14:28.800" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""would be very helpful.""" start="00:14:31.360" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""There's also some weird interfaces.""" start="00:14:32.640" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""For example, some things return identifiers""" start="00:14:35.320" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""as an array of integer code points instead of a string,""" start="00:14:38.120" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and there should be a common way of handling that.""" start="00:14:40.920" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""I also think that the service support could be improved.""" start="00:14:43.720" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Even though I gave the demo service,""" start="00:14:46.160" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""it's not really a great D-bus citizen""" start="00:14:48.040" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""because it doesn't offer that introspection mechanism,""" start="00:14:50.480" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""and so the actual methods are pretty much invisible""" start="00:14:53.080" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""to other participants,""" start="00:14:55.920" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""unless they already know that you're using Emacs.""" start="00:14:56.920" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""That's my talk.""" start="00:15:00.080" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""Thank you.""" start="00:15:01.800" video="mainVideo-dbus" id="subtitle"]]
[[!template text="""You can find me on mastodon.social or on libera.chat.""" start="00:15:02.560" video="mainVideo-dbus" id="subtitle"]]



Captioner: sachac

Questions or comments? Please e-mail [emacsconf-org-private@gnu.org](mailto:emacsconf-org-private@gnu.org?subject=Comment%20for%20EmacsConf%202022%20dbus%3A%20The%20Wheels%20on%20D-Bus)


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