path: root/2022/captions/emacsconf-2022-dbus--the-wheels-on-dbus--ian-eure--main.vtt

WEBVTT captioned by sachac

NOTE What is D-Bus?

00:00:00.000 --> 00:00:04.879
Welcome to my EmacsConf 2022 talk, The Wheels on D-Bus.

00:00:04.880 --> 00:00:07.439
In this talk, we'll cover what D-Bus is,

00:00:07.440 --> 00:00:10.759
why you might want to use it, and how to use it with Emacs.

00:00:10.760 --> 00:00:13.679
D-Bus is fundamentally based on passing messages

00:00:13.680 --> 00:00:16.999
in between processes, using the bus as a mediator.

00:00:17.000 --> 00:00:20.599
On top of this is built an RPC system with method invocation

00:00:20.600 --> 00:00:22.799
that has argument lists and return values,

00:00:22.800 --> 00:00:25.479
like you might find in any programming language.

00:00:25.480 --> 00:00:27.839
These are commonly used for verb-type actions

00:00:27.840 --> 00:00:29.999
like "restart my computer."

00:00:30.000 --> 00:00:32.639
You can also associate a collection of attributes

00:00:32.640 --> 00:00:35.839
with objects on the bus, and these are called properties.

00:00:35.840 --> 00:00:39.839
The properties can be read-only, write-only, or read-write.

00:00:39.840 --> 00:00:43.159
Signals are a way of notifying participants on the bus

00:00:43.160 --> 00:00:45.999
of updated state, and are the basis

00:00:46.000 --> 00:00:47.799
for building dynamic user interfaces

00:00:47.800 --> 00:00:50.479
that react to changes in the system.

00:00:50.480 --> 00:00:52.759
It has a static and strong type system,

00:00:52.760 --> 00:00:55.359
so if you send a message with the wrong type signature,

00:00:55.360 --> 00:00:57.839
it simply gets rejected instead of going through

00:00:57.840 --> 00:00:59.599
to the remote service.

00:00:59.600 --> 00:01:02.319
It also manages service life cycles,

00:01:02.320 --> 00:01:04.399
so you're not running services at all times.

00:01:04.400 --> 00:01:07.879
They can be started and stopped by D-Bus on demand.

NOTE Why D-Bus?

00:01:07.880 --> 00:01:10.519
D-Bus has two major use cases.

00:01:10.520 --> 00:01:13.359
The first is acting as a lower-level substrate

00:01:13.360 --> 00:01:14.679
for higher-level programs,

00:01:14.680 --> 00:01:16.919
like a graphical desktop environment.

00:01:16.920 --> 00:01:19.599
For example, if you want to manage your network connectivity

00:01:19.600 --> 00:01:21.239
from your graphical environment,

00:01:21.240 --> 00:01:23.919
instead of having to build all of that from the ground up,

00:01:23.920 --> 00:01:26.239
you can rely on the D-Bus service to do that

00:01:26.240 --> 00:01:28.679
and only build the graphical component of it.

00:01:28.680 --> 00:01:31.319
This gives you consistency between desktop environments

00:01:31.320 --> 00:01:33.799
and reduces code duplication.

00:01:33.800 --> 00:01:37.319
Another application is automating desktop programs.

00:01:37.320 --> 00:01:39.279
If your program offers a D-Bus service,

00:01:39.280 --> 00:01:40.959
then it can be remote-controlled,

00:01:40.960 --> 00:01:42.759
and if all of your programs offer D-Bus,

00:01:42.760 --> 00:01:45.359
you can control your entire desktop.

NOTE The D-Bus Model

00:01:45.360 --> 00:01:48.559
Let's look at the abstractions that D-Bus provides.

00:01:48.560 --> 00:01:51.239
The top level object is called a bus,

00:01:51.240 --> 00:01:52.359
and it's like a partition

00:01:52.360 --> 00:01:54.919
that messages get exchanged inside of.

00:01:54.920 --> 00:01:57.279
Messages don't cross buses.

00:01:57.280 --> 00:01:59.559
Inside of a bus are services.

00:01:59.560 --> 00:02:03.159
Services are normally identified in reverse FQDN order,

00:02:03.160 --> 00:02:06.159
so org.foobar.FooService.

00:02:06.160 --> 00:02:08.599
Each service provides some set of features

00:02:08.600 --> 00:02:11.759
related to a particular area of functionality.

00:02:11.760 --> 00:02:14.439
Inside of each service are objects.

00:02:14.440 --> 00:02:16.599
Objects use a path notation,

00:02:16.600 --> 00:02:19.759
and usually follow the same reverse FQDN format

00:02:19.760 --> 00:02:21.959
as the service identifier.

00:02:21.960 --> 00:02:24.879
Each object has one or more interfaces.

00:02:24.880 --> 00:02:27.279
An interface is like a facet that you can use

00:02:27.280 --> 00:02:29.479
to interact with an object,

00:02:29.480 --> 00:02:32.239
and inside of the interface are properties, methods,

00:02:32.240 --> 00:02:33.999
and signals, which we covered before.

00:02:34.000 --> 00:02:37.039
Properties are attributes that can be read or written.

00:02:37.040 --> 00:02:40.239
Methods are verbs that you can call to invoke an action,

00:02:40.240 --> 00:02:43.319
and a signal is something that's used to move state

00:02:43.320 --> 00:02:47.239
in between a service and another participant on the bus.

00:02:47.240 --> 00:02:49.599
There can be any number of interfaces on an object,

00:02:49.600 --> 00:02:51.479
any number of objects in a service,

00:02:51.480 --> 00:02:53.439
and any number of services on a bus,

00:02:53.440 --> 00:02:55.359
and any number of buses on a system.

NOTE Well-known Busses

00:02:55.360 --> 00:03:00.039
There are two well-known busses,

00:03:00.040 --> 00:03:02.359
and these roughly map to those two use cases

00:03:02.360 --> 00:03:03.639
I mentioned before.

00:03:03.640 --> 00:03:06.479
The system bus is for interfacing with hardware

00:03:06.480 --> 00:03:08.439
and operating-system-level concerns

00:03:08.440 --> 00:03:11.679
like disks, networks, and so forth.

00:03:11.680 --> 00:03:14.319
The session bus is tied to a user login,

00:03:14.320 --> 00:03:19.999
and is more in the desktop automation use case.

NOTE Common interfaces

00:03:20.000 --> 00:03:21.919
There are some common interfaces you'll find

00:03:21.920 --> 00:03:23.959
if you go exploring D-Bus.

00:03:23.960 --> 00:03:25.999
The Introspectable interface is the basis

00:03:26.000 --> 00:03:27.919
of a lot of the reflection features.

00:03:27.920 --> 00:03:30.119
It has a single method called introspect

00:03:30.120 --> 00:03:32.239
that returns the XML interface description

00:03:32.240 --> 00:03:33.399
of whatever you call it on.

00:03:33.400 --> 00:03:36.559
Peer is used for lower level connectivity,

00:03:36.560 --> 00:03:39.679
for example, pinging a service to see if it's running.

00:03:39.680 --> 00:03:41.759
And the Properties interface is the basis

00:03:41.760 --> 00:03:43.119
of the read-write properties,

00:03:43.120 --> 00:03:45.799
which are secretly method calls under the cover.

00:03:45.800 --> 00:03:48.519
Just about every object you interact with on D-Bus

00:03:48.520 --> 00:03:51.399
will support all three of these interfaces.

00:03:51.400 --> 00:03:54.759
Additionally, ObjectManager is used for services

00:03:54.760 --> 00:03:56.759
that manage collections of objects.

00:03:56.760 --> 00:03:59.839
For example, the disk service has an object

00:03:59.840 --> 00:04:01.279
for each disk that's attached,

00:04:01.280 --> 00:04:02.799
and the object manager allows you

00:04:02.800 --> 00:04:06.239
to enumerate all of those.

NOTE Emacs Native D-Bus

00:04:06.240 --> 00:04:10.359
Emacs supports D-Bus natively since version 23.1.

00:04:10.360 --> 00:04:12.119
It's a combination of native bindings

00:04:12.120 --> 00:04:14.639
with a C library and dbus.el.

00:04:14.640 --> 00:04:17.559
While there are some ports of D-Bus

00:04:17.560 --> 00:04:19.479
to non-Linux operating systems,

00:04:19.480 --> 00:04:22.039
it's probably only available on Linux

00:04:22.040 --> 00:04:24.439
and almost certainly only usable on Linux.

00:04:24.440 --> 00:04:28.919
If you want to interact with D-Bus from Emacs,

00:04:28.920 --> 00:04:30.079
it's fairly straightforward.

00:04:30.080 --> 00:04:33.199
There's a collection of functions like dbus-get-property

00:04:33.200 --> 00:04:35.039
or dbus-call-method, et cetera,

00:04:35.040 --> 00:04:37.639
and they almost all take this same set

00:04:37.640 --> 00:04:39.319
of four arguments at the beginning:

00:04:39.320 --> 00:04:42.119
bus, service, path, and interface.

00:04:42.120 --> 00:04:45.439
In this case, it takes a single additional property,

00:04:45.440 --> 00:04:46.599
which is the one to read.

00:04:46.600 --> 00:04:49.679
And what we're calling is the hostname1 service,

00:04:49.680 --> 00:04:51.519
which gives you just a little bit of information

00:04:51.520 --> 00:04:54.759
about the system, like its hostname or its chassis.

00:04:54.760 --> 00:04:56.199
And in this case, you can see I'm running

00:04:56.200 --> 00:04:57.719
this presentation off my laptop.

00:04:57.720 --> 00:05:00.959
The problem with this and what I don't like about it

00:05:00.960 --> 00:05:04.599
is that all of these identifiers are very verbose

00:05:04.600 --> 00:05:05.719
and very repetitive.

00:05:05.720 --> 00:05:07.679
And if you end up calling these a lot,

00:05:07.680 --> 00:05:09.319
it gets old really quickly.

NOTE Debase

00:05:09.320 --> 00:05:12.999
So I wrote a wrapper called Debase,

00:05:13.000 --> 00:05:15.839
which is convenience on top of the built-in functions.

00:05:15.840 --> 00:05:18.839
Most of the stock functions have Debase versions

00:05:18.840 --> 00:05:21.519
just by replacing "dbus" with "debase".

00:05:21.520 --> 00:05:23.879
And let's look how that works.

NOTE Debase: Objects

00:05:23.880 --> 00:05:27.999
The fundamental idea of Debase is that you can bind together

00:05:28.000 --> 00:05:30.319
all of those arguments into a single object

00:05:30.320 --> 00:05:31.559
that represents the endpoint.

00:05:31.560 --> 00:05:35.599
This is an EIEIO class, and it takes keyword arguments,

00:05:35.600 --> 00:05:36.879
so there's never any chance

00:05:36.880 --> 00:05:38.559
of mixing up which thing is what.

00:05:38.560 --> 00:05:41.479
So this sets the endpoint to that object,

00:05:41.480 --> 00:05:43.119
calls debase-get-property on it,

00:05:43.120 --> 00:05:45.039
and you can see it works exactly the same.

00:05:45.040 --> 00:05:47.359
The thing that's really nice about this, though,

00:05:47.360 --> 00:05:50.199
is it knows that so many of these arguments

00:05:50.200 --> 00:05:52.919
are very similar that it can compute most of them

00:05:52.920 --> 00:05:54.279
if you don't provide them all.

00:05:54.280 --> 00:05:57.159
So if you just say service, it will assume

00:05:57.160 --> 00:05:59.159
that you want the same object that matches

00:05:59.160 --> 00:06:00.879
and the same interface that matches,

00:06:00.880 --> 00:06:02.319
and it works just the same.

00:06:02.320 --> 00:06:04.879
I find this very, very convenient.

00:06:04.880 --> 00:06:07.239
You can also reuse the object

00:06:07.240 --> 00:06:09.159
instead of having to repeat every argument

00:06:09.160 --> 00:06:10.399
with every function call,

00:06:10.400 --> 00:06:13.439
which is a really great improvement in ergonomics.

NOTE Debase: Retarget objects

00:06:13.440 --> 00:06:18.119
Because so many objects have multiple interfaces,

00:06:18.120 --> 00:06:20.319
you often find yourself needing to look

00:06:20.320 --> 00:06:22.479
at a different aspect of that object.

00:06:22.480 --> 00:06:26.599
This is supported with the built-in EIEIO clone method,

00:06:26.600 --> 00:06:28.279
which takes an object

00:06:28.280 --> 00:06:30.439
and a set of keyword arguments to replace.

00:06:30.440 --> 00:06:32.599
So in this case, we can see we're calling

00:06:32.600 --> 00:06:33.479
the Properties method,

00:06:33.480 --> 00:06:35.799
but everything else on that endpoint is the same.

00:06:35.800 --> 00:06:38.079
And then we're gonna call the method GetAll

00:06:38.080 --> 00:06:39.359
on that Properties interface,

00:06:39.360 --> 00:06:41.119
and it's going to return all the properties

00:06:41.120 --> 00:06:43.919
of the org.freedesktop.hostname1 interface

00:06:43.920 --> 00:06:45.199
inside of that object.

00:06:45.200 --> 00:06:48.199
And if we run that, we can see there's the hostname

00:06:48.200 --> 00:06:50.159
and some other information about the laptop

00:06:50.160 --> 00:06:51.079
that I'm running this on.

NOTE Debase: Object binding

00:06:51.080 --> 00:06:54.399
Debase also supports object binding.

00:06:54.400 --> 00:06:58.559
This creates a lexical context in which the Debase object

00:06:58.560 --> 00:07:01.119
is the implicit target of any D-Bus function.

00:07:01.120 --> 00:07:03.279
This is really convenient if you need

00:07:03.280 --> 00:07:06.479
to fetch multiple properties or otherwise interact

00:07:06.480 --> 00:07:09.319
with the same endpoint in multiple different ways.

00:07:09.320 --> 00:07:11.359
And you can see I'm still on a laptop

00:07:11.360 --> 00:07:12.479
and it's still named meson.

NOTE Debase: Raw binding

00:07:12.480 --> 00:07:16.319
You can also, if you don't want to use the object,

00:07:16.320 --> 00:07:18.239
you can provide the raw argument list.

00:07:18.240 --> 00:07:20.919
Under the covers, this is basically an flet

00:07:20.920 --> 00:07:23.279
where you're currying all of these functions

00:07:23.280 --> 00:07:25.439
so they start with those argument lists.

00:07:25.440 --> 00:07:27.799
And you can see I'm running on a Linux machine,

00:07:27.800 --> 00:07:29.399
which should not be surprising.

NOTE Debase: Codegen

00:07:29.400 --> 00:07:34.079
Debase also has an experimental code generation feature.

00:07:34.080 --> 00:07:38.359
It outputs EIEIO code with one class per D-Bus interface.

00:07:38.360 --> 00:07:41.079
This includes accessors for all of its properties

00:07:41.080 --> 00:07:44.159
with an in-process cache, so if you read one property,

00:07:44.160 --> 00:07:46.399
you don't have to go back to the bus to read it again.

00:07:46.400 --> 00:07:50.119
It also outputs generic functions and method implementations

00:07:50.120 --> 00:07:52.199
for the D-Bus interface methods.

00:07:52.200 --> 00:07:54.279
It includes name-mangling options,

00:07:54.280 --> 00:07:56.879
so you can control how everything is named.

00:07:56.880 --> 00:07:58.639
And you can generate the code either

00:07:58.640 --> 00:08:00.279
via introspecting a live system

00:08:00.280 --> 00:08:02.639
or providing an XML interface description,

00:08:02.640 --> 00:08:04.279
which is handy if you want to use it

00:08:04.280 --> 00:08:05.919
as part of a non-interactive build.

00:08:05.920 --> 00:08:08.159
I think this has a lot of promise,

00:08:08.160 --> 00:08:09.679
but it doesn't feel quite right yet,

00:08:09.680 --> 00:08:14.199
so any feedback or contributions are very welcome.

NOTE Debase: Codegen example

00:08:14.200 --> 00:08:16.919
Let's generate some Elisp code

00:08:16.920 --> 00:08:19.639
for that hostname1 service we were interacting with before.

00:08:19.640 --> 00:08:23.119
debase-gen-class is the generation class,

00:08:23.120 --> 00:08:26.079
and it says to create a class that matches this interface,

00:08:26.080 --> 00:08:28.999
named "hostname1", and then the rest of these arguments

00:08:29.000 --> 00:08:30.999
are the same ones to target the endpoint,

00:08:31.000 --> 00:08:32.919
just like with debase-object,

00:08:32.920 --> 00:08:34.759
because it extends debase-object.

00:08:34.760 --> 00:08:37.679
debase-gen-code is a generic function

00:08:37.680 --> 00:08:40.119
that takes any debase-gen class.

00:08:40.120 --> 00:08:42.279
There are different classes for functions,

00:08:42.280 --> 00:08:43.359
properties, et cetera,

00:08:43.360 --> 00:08:45.479
and it creates all of the code for it.

00:08:45.480 --> 00:08:48.279
If we evaluate it, we can see the results

00:08:48.280 --> 00:08:49.959
look about like we would expect:

00:08:49.960 --> 00:08:52.159
creates a defclass named "hostname1",

00:08:52.160 --> 00:08:53.879
which extends debase-object,

00:08:53.880 --> 00:08:56.639
has all of the slots and accessors defined,

00:08:56.640 --> 00:08:59.319
and then methods that define everything

00:08:59.320 --> 00:09:01.839
that you might want to do with it, including documentation.

00:09:01.840 --> 00:09:04.759
This is based on introspecting a running system,

00:09:04.760 --> 00:09:05.479
but as I mentioned,

00:09:05.480 --> 00:09:08.039
you can provide an XML interface description instead,

00:09:08.040 --> 00:09:08.679
if you like.

NOTE Debase: ObjectManager

00:09:08.680 --> 00:09:12.279
Debase also comes with "debase-objectmanager",

00:09:12.280 --> 00:09:15.399
which is convenience for the D-Bus ObjectManager interface.

00:09:15.400 --> 00:09:17.999
This is used in a lot of places in D-Bus,

00:09:18.000 --> 00:09:20.279
where an object manages other objects.

00:09:20.280 --> 00:09:22.719
For example, the NetworkManager object

00:09:22.720 --> 00:09:25.159
manages network hardware objects,

00:09:25.160 --> 00:09:26.879
and using the ObjectManager interface,

00:09:26.880 --> 00:09:28.879
you can enumerate all of the network hardware,

00:09:28.880 --> 00:09:31.039
and by subscribing to the signals,

00:09:31.040 --> 00:09:32.999
you can be notified when they change.

00:09:33.000 --> 00:09:35.999
"debase-objectmanager" keeps a local cache,

00:09:36.000 --> 00:09:38.119
and will fire a callback on any change.

00:09:38.120 --> 00:09:41.239
So it's the building block for that dynamic user interface,

00:09:41.240 --> 00:09:43.119
like you would see in a desktop system,

00:09:43.120 --> 00:09:44.479
but inside of Emacs.

NOTE Demo: Discomfort

00:09:44.480 --> 00:09:47.759
Let's do some demos.

00:09:47.760 --> 00:09:51.039
Discomfort is an interface I wrote for UDisks2,

00:09:51.040 --> 00:09:53.719
which is what manages all of the block device hardware.

00:09:53.720 --> 00:09:57.679
And again, it has that dynamic desktop-like interactivity,

00:09:57.680 --> 00:10:00.279
and mostly will just do what you mean.

00:10:00.280 --> 00:10:03.519
This is definitely alpha state.

00:10:03.520 --> 00:10:04.839
It doesn't have all the features,

00:10:04.840 --> 00:10:06.559
but it's good enough that I use it daily.

00:10:06.560 --> 00:10:08.879
So here's Discomfort,

00:10:08.880 --> 00:10:11.679
and you can see it has a list of all your hardware,

00:10:11.680 --> 00:10:13.639
what type it is, and where it's mounted.

00:10:13.640 --> 00:10:16.199
I have a little USB extension cable here,

00:10:16.200 --> 00:10:17.679
and I'm gonna plug in a disc,

00:10:17.680 --> 00:10:19.319
just to show you how this works.

00:10:19.320 --> 00:10:21.079
You can see when I plug it in,

00:10:21.080 --> 00:10:22.399
just a moment later,

00:10:22.400 --> 00:10:24.439
it shows up in that list, automatically.

00:10:24.440 --> 00:10:25.719
I don't have to press any key,

00:10:25.720 --> 00:10:27.759
I don't have to refresh it, it's just there.

00:10:27.760 --> 00:10:29.519
If I unplug it, it's gone.

00:10:29.520 --> 00:10:30.719
Plug it back in,

00:10:30.720 --> 00:10:33.399
and there it is.

00:10:33.400 --> 00:10:35.239
And you can see it's an encrypted volume.

00:10:35.240 --> 00:10:37.279
So in order to do anything with this,

00:10:37.280 --> 00:10:38.679
I'm going to have to supply a password.

00:10:38.680 --> 00:10:41.759
Just pressing Enter goes into the "do what I mean" mode,

00:10:41.760 --> 00:10:43.519
and it asks for the password.

00:10:43.520 --> 00:10:46.599
In this case, I've chosen the very secure password

00:10:46.600 --> 00:10:47.559
of "password".

00:10:47.560 --> 00:10:51.199
I hit Enter, and it unlocks it, and it mounts it,

00:10:51.200 --> 00:10:53.319
and it opens "dired" looking at it.

00:10:53.320 --> 00:10:54.439
And here's a little README.

00:10:54.440 --> 00:10:55.559
Let's see what it says.

00:10:55.560 --> 00:10:58.559
"Hello, EmacsConf."

00:10:58.560 --> 00:11:01.479
So that's my demo of discomfort.

NOTE Demo: Remote eval

00:11:01.480 --> 00:11:05.839
In addition to acting as a client for D-Bus,

00:11:05.840 --> 00:11:09.359
Emacs can also offer services to other D-Bus clients.

00:11:09.360 --> 00:11:11.959
This is a really interesting opportunity

00:11:11.960 --> 00:11:14.119
because it allows many different programs

00:11:14.120 --> 00:11:15.279
to integrate with Emacs

00:11:15.280 --> 00:11:17.679
in ways that were previously very difficult.

00:11:17.680 --> 00:11:20.239
You can use this as an alternative to Emacs.

00:11:20.240 --> 00:11:23.199
The difference is D-Bus provides a full API,

00:11:23.200 --> 00:11:24.999
so instead of emacsclient being

00:11:25.000 --> 00:11:26.679
a sort of fire-and-forget system,

00:11:26.680 --> 00:11:30.119
you can actually get results back from the remote operation.

00:11:30.120 --> 00:11:31.999
So here's some code.

00:11:32.000 --> 00:11:35.679
Here's a dbus-eval function, which takes a string,

00:11:35.680 --> 00:11:37.359
reads it, and evaluates it,

00:11:37.360 --> 00:11:39.359
and returns whatever that value is.

00:11:39.360 --> 00:11:41.839
Then we have a debase-bind block

00:11:41.840 --> 00:11:44.799
that sets up an object on the session bus.

00:11:44.800 --> 00:11:46.839
Again, that's my user login bus.

00:11:46.840 --> 00:11:49.559
It offers this D-Bus service Emacs.

00:11:49.560 --> 00:11:53.399
This is a constant inside of the dbus.el package.

00:11:53.400 --> 00:11:55.439
And again, the path is a constant in there.

00:11:55.440 --> 00:11:57.159
And we're gonna create this interface,

00:11:57.160 --> 00:12:02.519
org.gnu.Emacs.Eval, and then register a method called Eval

00:12:02.520 --> 00:12:04.759
that calls that dbus-eval function.

00:12:04.760 --> 00:12:08.119
Pretty straightforward, only a handful of lines of code.

00:12:08.120 --> 00:12:12.399
To test this out, we're going to use the dbus-send utility.

00:12:12.400 --> 00:12:15.399
This is a command line program that interacts with D-Bus.

00:12:15.400 --> 00:12:18.079
We're going to tell it to wait for and print the reply,

00:12:18.080 --> 00:12:20.999
that the message should be sent to the session bus,

00:12:21.000 --> 00:12:22.599
that we're going to talk

00:12:22.600 --> 00:12:25.639
to the org.gnu.Emacs service on that bus,

00:12:25.640 --> 00:12:30.879
and the /org/gnu/Emacs object inside that service.

00:12:30.880 --> 00:12:33.039
On that object, we're gonna interact

00:12:33.040 --> 00:12:35.999
with the org.gnu.Emacs.Eval interface

00:12:36.000 --> 00:12:37.639
and call its Eval method.

00:12:37.640 --> 00:12:40.639
We're gonna call that method with a single string argument,

00:12:40.640 --> 00:12:42.639
which is indicated by the string prefix,

00:12:42.640 --> 00:12:44.999
and then a form to evaluate.

00:12:45.000 --> 00:12:46.999
I actually have to run this from a shell,

00:12:47.000 --> 00:12:49.399
because if I try using it in Org, it wedges.

00:12:49.400 --> 00:12:51.959
org-babel blocks waiting on completion,

00:12:51.960 --> 00:12:54.519
which blocks the D-Bus service from responding.

00:12:54.520 --> 00:12:57.399
I really wish Emacs was multi-threaded.

00:12:57.400 --> 00:12:59.919
But let's try it out.

00:12:59.920 --> 00:13:02.719
So if we run this, we can see that we get a return,

00:13:02.720 --> 00:13:05.239
and that's an unsigned integer of 32 bits

00:13:05.240 --> 00:13:06.439
with a value of 3.

00:13:06.440 --> 00:13:09.959
So like I was saying, this is really a two-way API

00:13:09.960 --> 00:13:11.719
where you can communicate back and forth

00:13:11.720 --> 00:13:13.399
between Emacs and another program.

00:13:13.400 --> 00:13:14.959
It's not just fire-and-forget.

00:13:14.960 --> 00:13:16.279
I think that's really cool.

NOTE Demo: Remote Org capture

00:13:16.280 --> 00:13:18.519
Let's try another demo.

00:13:18.520 --> 00:13:20.599
What about a remote org-capture?

00:13:20.600 --> 00:13:22.999
What if you could trigger an org-capture

00:13:23.000 --> 00:13:24.679
from any program on your desktop?

00:13:24.680 --> 00:13:26.239
I think that would be pretty cool.

00:13:26.240 --> 00:13:30.239
And we can see, there it is.

00:13:30.240 --> 00:13:38.919
All right, I think I've got that one covered.

00:13:38.920 --> 00:13:42.319
So I do want to say that remote eval is probably a bad idea

00:13:42.320 --> 00:13:43.479
from a security perspective,

00:13:43.480 --> 00:13:46.759
but the point of this is some quick and dirty demonstrations

00:13:46.760 --> 00:13:49.799
of what can happen and to get people's imaginations flowing,

00:13:49.800 --> 00:13:51.719
because I think this is something

00:13:51.720 --> 00:13:54.079
that offers a lot of promise for Emacs.

00:13:54.080 --> 00:13:57.799
I think having a full-blown Emacs desktop environment

00:13:57.800 --> 00:13:59.879
where it can do all the things that a GNOME

00:13:59.880 --> 00:14:02.759
or a KDE environment can do is very exciting.

00:14:02.760 --> 00:14:06.439
And if you want to have a traditional GUI with Emacs

00:14:06.440 --> 00:14:08.679
as a more integrated participant of it,

00:14:08.680 --> 00:14:11.879
its service mechanism offers a lot of ability to do that.

NOTE Future directions

00:14:11.880 --> 00:14:15.999
In the micro sense, I think there's a lot of improvements

00:14:16.000 --> 00:14:19.279
that can be made to either dbus.el or to dbase.

00:14:19.280 --> 00:14:21.639
The main one is handling of the type system.

00:14:21.640 --> 00:14:25.839
Lisp's dynamic type system doesn't mesh particularly well

00:14:25.840 --> 00:14:28.799
with the static strong type system that D-bus offers,

00:14:28.800 --> 00:14:31.359
and having some convenience to assist that

00:14:31.360 --> 00:14:32.639
would be very helpful.

00:14:32.640 --> 00:14:35.319
There's also some weird interfaces.

00:14:35.320 --> 00:14:38.119
For example, some things return identifiers

00:14:38.120 --> 00:14:40.919
as an array of integer code points instead of a string,

00:14:40.920 --> 00:14:43.719
and there should be a common way of handling that.

00:14:43.720 --> 00:14:46.159
I also think that the service support could be improved.

00:14:46.160 --> 00:14:48.039
Even though I gave the demo service,

00:14:48.040 --> 00:14:50.479
it's not really a great D-bus citizen

00:14:50.480 --> 00:14:53.079
because it doesn't offer that introspection mechanism,

00:14:53.080 --> 00:14:55.919
and so the actual methods are pretty much invisible

00:14:55.920 --> 00:14:56.919
to other participants,

00:14:56.920 --> 00:15:00.079
unless they already know that you're using Emacs.

00:15:00.080 --> 00:15:01.799
That's my talk.

00:15:01.800 --> 00:15:02.559
Thank you.

00:15:02.560 --> 00:15:07.320
You can find me on mastodon.social or on libera.chat.