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diff --git a/2022/captions/emacsconf-2022-dbus--the-wheels-on-dbus--ian-eure--main--chapters.vtt b/2022/captions/emacsconf-2022-dbus--the-wheels-on-dbus--ian-eure--main--chapters.vtt new file mode 100644 index 00000000..cc47a738 --- /dev/null +++ b/2022/captions/emacsconf-2022-dbus--the-wheels-on-dbus--ian-eure--main--chapters.vtt @@ -0,0 +1,55 @@ +WEBVTT + +00:00:00.000 --> 00:01:07.879 +What is D-Bus? + +00:01:07.880 --> 00:01:45.359 +Why D-Bus? + +00:01:45.360 --> 00:02:55.359 +The D-Bus Model + +00:02:55.360 --> 00:03:19.999 +Well-known Busses + +00:03:20.000 --> 00:04:06.239 +Common interfaces + +00:04:06.240 --> 00:05:09.319 +Emacs Native D-Bus + +00:05:09.320 --> 00:05:23.879 +Debase + +00:05:23.880 --> 00:06:13.439 +Debase: Objects + +00:06:13.440 --> 00:06:51.079 +Debase: Retarget objects + +00:06:51.080 --> 00:07:12.479 +Debase: Object binding + +00:07:12.480 --> 00:07:29.399 +Debase: Raw binding + +00:07:29.400 --> 00:08:14.199 +Debase: Codegen + +00:08:14.200 --> 00:09:08.679 +Debase: Codegen example + +00:09:08.680 --> 00:09:44.479 +Debase: ObjectManager + +00:09:44.480 --> 00:11:01.479 +Demo: Discomfort + +00:11:01.480 --> 00:13:16.279 +Demo: Remote eval + +00:13:16.280 --> 00:14:11.879 +Demo: Remote Org capture + +00:14:11.880 --> 00:15:07.320 +Future directions diff --git a/2022/captions/emacsconf-2022-dbus--the-wheels-on-dbus--ian-eure--main.vtt b/2022/captions/emacsconf-2022-dbus--the-wheels-on-dbus--ian-eure--main.vtt new file mode 100644 index 00000000..7420e30c --- /dev/null +++ b/2022/captions/emacsconf-2022-dbus--the-wheels-on-dbus--ian-eure--main.vtt @@ -0,0 +1,1126 @@ +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. |