Move application framework section

Move application framework section from "Developer Guides" to
"Component Documentation" and fix all links.

Bug-AGL: SPEC-4928

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: I6bb10908860860d6634b23f6a458959397a98e81
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/documentation/+/29283
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
Tested-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>

9 files changed, 0 insertions, 973 deletions

diff --git a/docs/04_Developer_Guides/01_Application_Framework/01_Introduction.md b/docs/04_Developer_Guides/01_Application_Framework/01_Introduction.md
deleted file mode 100644
index 4084032..0000000
--- a/docs/04_Developer_Guides/01_Application_Framework/01_Introduction.md
+++ /dev/null
@@ -1,186 +0,0 @@
----
-title: Introduction
----
-
-# Foreword
-
-The AGL Application Framework is nothing new. However, the implementation used
-up until the `lamprey` release has been retired starting with the `marlin`
-release and replaced by a redesigned Application Framework one. However, this
-new implementation isn't a 1:1 replacement, and as such it doesn't provide all
-of the features of the previous Application Framework. Some of those will be
-added back over time, others have been discarded in favor of more modern and/or
-widely-used alternatives.
-
-With the `needlefish` release, further changes have been added, including a
-[gRPC IPC](https://grpc.io/about), alongside a deprecated D-Bus one, as well as
-using as using systemd units as opposed on using
-[Desktop Entry specification](https://www.freedesktop.org/wiki/Specifications/desktop-entry-spec/)
-to list applications, and relies entirely on systemd to start application,
-rather than spawning them directly.
-
-Once all platforms transitioned to gRPC, the D-Bus functionality will be
-removed entirely, mentioning it in only in documentation for history purposes.
-
-# Introduction
-
-As a provider of an integrated solution to build up on, AGL needs to define a
-reliable and well-specified method for managing the deployment and integration
-of applications and services, as well as the way they can interact with the
-rest of the system.
-
-This is achieved by providing a common set of rules and components, known as
-the Application Framework. By ensuring conformity to those rules, application
-developers can have a good understanding of the requirements for creating and
-packaging applications targeting AGL-based systems. Likewise, system developers
-and integrators have a clear path for including such applications in AGL-based
-products.
-
-The Application Framework's scope extends to the following areas:
-- system services integration and lifecycle management
-- user session management, including user-level applications and services
-  lifecycle management
-- inter-process communication
-
-In order to be as simple as possible and avoid any unneeded custom
-implementation, the Application Framework relies mainly on third-party
-technologies and/or software components, most of those being maintained under
-the [freedesktop.org](https://www.freedesktop.org) umbrella. Those include:
-
-
-- [systemd](https://www.freedesktop.org/wiki/Software/systemd/): system
-  services and user session services management
-
-
-- [D-Bus](https://www.freedesktop.org/wiki/Software/dbus/): inter-process
-  communication, with `needlefish' release deprecated phase.
-
-- [gRPC](https://grpc.io/about): inter-process communication, new recommmended
-  system-wide IPC, which should be used instead of D-Bus.
-
-
-- [Desktop Entry specification](https://www.freedesktop.org/wiki/Specifications/desktop-entry-spec/):
-  application enumeration and startup, now in deprecated phase, systemd being
-  the one would list out applications and handling start-up.
-
-AGL also provides reference implementations whenever possible and relevant,
-located in the [meta-agl](/04_Developer_Guides/02_AGL_Layers/02_meta_agl/)
-layer under `meta-app-framework`. At the moment, the Application Framework
-contains 2 such components:
-
-- `agl-session`: `systemd` unit files for user sessions management
-
-- `applaunchd`: application launcher service
-
-# Services management
-
-Both system and user services are managed by `systemd`, which provides a number
-of important features, such as dependency management or service monitoring:
-when starting a service, `systemd` will ensure any other units this service
-depends on are available, and otherwise start those dependencies. Similarly,
-`systemd` can automatically restart a crashed service, ensuring minimal
-downtime.
-
-`systemd` also provides an efficient first layer of security through its
-[sandboxing](https://www.freedesktop.org/software/systemd/man/systemd.exec.html#Sandboxing)
-and other security-related options.
-
-It is also well integrated with D-Bus and can be used for a more fine-grained
-control over D-Bus activated services: by delegating the actual service startup
-to `systemd`, developers can take advantage of some of its advanced features,
-allowing for improved reliability and security.
-
-Each service should be represented by a `systemd` unit file installed to the
-appropriate location. More details can be obtained from the [Creating a New
-Service](../03_Creating_a_New_Service/) document.
-
-# User session management
-
-Similarly, user sessions and the services they rely on are also managed by
-`systemd`.
-
-AGL provides 2 `systemd` units:
-
-
-1\. `agl-session@.service` is a template system service for managing user
-sessions; it takes a username or UID as a parameter, creating a session for the
-desired user.  Instanciating this service can be achieved by enabling
-`agl-session@USER.service`, for example by executing the following command on a
-running system:
-
-```
-$ systemctl enable agl-session@USER.service
-```
-
-By default, AGL enables this service as `agl-session@agl-driver.service`,
-running as user `agl-driver`.
-
-*Note: while you can create sessions for as many users as needed, only one
-instance of `agl-session@.service` is allowed per user.*
-
-
-2\. `agl-session.target` is a user target for managing user services and their
-dependencies. It is started by `agl-session@.service`.
-
-By default, `agl-compositor` is part of this target. It is therefore
-automatically started for user `agl-driver`.
-
-Any other service needed as part of the user session should similarly depend on
-this target by appending the following lines to their unit file:
-
-```
-[Install]
-WantedBy=agl-session.target
-```
-
-# Inter-process communication
-
-In order to provide a "standard", language-independent IPC mechanism and avoid
-the need for maintaining custom bindings for each programming language to be
-used on top of AGL, the Application Framework used to promote the use of
-[D-Bus](https://www.freedesktop.org/wiki/Software/dbus/) as the preferred way
-for applications to interact with services. Starting with `needlefish` release,
-we instead switched to using [gRPC](https://grpc.io) for our system-wide IPC,
-with D-Bus being kept to provide functionality to services and application
-which haven't transitioned yet to using gRPC.
-
-Most services already included in AGL provide one or several D-Bus interfaces,
-and can therefore interact with D-Bus capable applications and services
-without requiring any additional component. Those services include, among
-others:
-
-- [ConnMan](https://git.kernel.org/pub/scm/network/connman/connman.git/):
-  network connectivity
-
-- [BlueZ](http://www.bluez.org/): Bluetooth connectivity
-
-- [oFono](https://git.kernel.org/pub/scm/network/ofono/ofono.git): telephony
-  and modem management
-
-- [GeoClue](https://gitlab.freedesktop.org/geoclue/geoclue/-/wikis/home):
-  geolocation
-
-Similarly, we're in the phase of expanding various services to expose a
-gRPC interface.
-
-# Application launcher service
-
-The Application Framework used to follow the guidelines of the [Desktop Entry
-specification](https://www.freedesktop.org/wiki/Specifications/desktop-entry-spec/)
-for application enumeration and startup, but with the `needlefish` release
-instead it relies on systemd to provide that functionality, indirectly, by
-using the `applaunchd` application.
-
-As no simple reference implementation exists for this part of the
-specification, AGL provides an application launcher service named `applaunchd`.
-This service is part of the default user session, and as such is automatically
-started on session startup. It can therefore be considered always available.
-
-`applaunchd` enumerates applications installed on the system and provides a
-D-bus (deprecated)/gRPC interface for services and applications to:
-- query the list of available applications
-- request the startup and/or activation of a specific application
-- be notified when applications are started or terminated
-
-`applaunchd` with the D-Bus interface is described with more details in
-[the following document](../02_Application_Startup_Dbus/).
diff --git a/docs/04_Developer_Guides/01_Application_Framework/02_Application_Startup.md b/docs/04_Developer_Guides/01_Application_Framework/02_Application_Startup.md
deleted file mode 100644
index 56876a4..0000000
--- a/docs/04_Developer_Guides/01_Application_Framework/02_Application_Startup.md
+++ /dev/null
@@ -1,248 +0,0 @@
----
-title: Application Startup
----
-
-# Introduction
-
-At system runtime, it may be necessary for applications to start other
-applications on demand. Such actions can be executed in reaction to a user
-request, or they may be needed to perform a specific task.
-
-In order to do so, running applications and services need an established way of
-discovering installed applications and executing those.
-
-In order to provide a language-independent interface for applications and
-service to use, AGL includes `applaunchd`, a system service.
-
-# Application launcher service
-
-The purpose of `applaunchd` is to enumerate applications available on the
-system and provide a way for other applications to query this list and start
-those on demand.  It is also able to notify clients of the startup and
-termination of applications it manages.
-
-To that effect, `applaunchd` provides a gRPC interface which other applications
-can use in order to execute those actions.
-
-*Note: `applaunchd` will only send notifications for applications it started;
-it isn't aware of applications started by other means (`systemd`, direct
-executable call...), and therefore can't send notifications for those.*
-
-## Application discovery
-
-Applications are enumerated from systemd's list of available units based on the
-pattern `agl-app*@*.service`, and are started and controled using their systemd
-unit.  Please note `applaunchd` allows only one instance of a given
-application.
-
-## Application identifiers
-
-Each application is identified by a unique Application ID. Although this ID can
-be any valid string, it is highly recommended to use the "reverse DNS"
-convention in order to avoid potential name collisions.
-
-## gRPC interface
-
-The interface provides methods for the following actions:
-
-- retrieve the list of available applications
-- request an application to be started
-- subscribe to status events
-
-Moreover, with the gRPC the client subscribes to a status signal to be notified
-when an application has successfully started or its execution terminated.
-
-The gRPC protobuf file provides a Request and Response arguments to RPC methods
-even though in some cases these might be empty in order to allow forward
-compatibility in case additional fields are required.
-It is a good standard practice to follow up with these recommendation when
-developing a new protobuf specification.
-
-### Applications list
-
-The `ListApplications` method allows clients to retrieve the list of available
-applications. 
-
-The `ListRequest` is an empty message, while `ListResponse` contains the following:
-
-```
-message AppInfo {
-  string id = 1;
-  string name = 2;
-  string icon_path = 3;
-}
-
-message ListResponse {
-  repeated AppInfo apps = 1;
-}
-```
-
-### Application startup request
-
-Applications can be started by using the `StartApplication` method, passing the
-`StartRequest` message, defined as:
-
-```
-message StartRequest {
-  string id = 1;
-}
-```
-
-In reply, the following `StartResponse` will be returned:
-
-```
-message StartResponse {
-  bool status = 1;
-  string message = 2;
-}
-```
-
-The "message" string  of `StartResponse` message will contain an error message
-in case we couldn't start the application for whatever reason, or if the "id"
-isn't a known application ID. The "status" string would be boolean set to
-boolean `TRUE` otherwise.
-
-If the application is already running, `applaunchd` won't start another
-instance, but instead reply with a `AppStatus` message setting the `status`
-string to "started".
-
-### Status notifications
-
-The gRPC interface provides clients with a subscription model to receive
-status events. Client should subscribe to `GetStatusEvents` method to receive
-them.
-
-The `StatusRequest` is empty, while the `StatusResponse` is defined as
-following:
-
-```
-message AppStatus {
-  string id = 1;
-  string status = 2;
-}
-
-message LauncherStatus {
-}
-
-message StatusResponse {
-  oneof status {
-    AppStatus app = 1;
-    LauncherStatus launcher = 2;
-  }
-}
-```
-
-As mentioned above, the `status` string is set to "started" and is also emitted
-if `applaunchd` receives a request to start an already running application.
-This can be useful, for example, when switching between graphical applications:
-
-- the application switcher doesn't need to track the state of each application;
-  instead, it can simply send a `StartApplication` request to `applaunchd`
-  every time the user requests to switch to another application. Obviously, the
-  client needs to subscribe to get these events and act accordingly.
-- the shell client then receives the `StatusResponse` with the message `status`
-  string set to "started" indicating it that it should activate the window with
-  the corresponding `id` string, or alternatively the string `status` is
-  set to "terminated" to denote that the application has been terminated,
-  forcibly or not
-
-## A deeper look at start-up, activation and application switching
-
-Application start-up, activation and application switching are sometimes
-conflated into a single operation but underneath some of these are distinct
-steps, and a bit flaky in some circumstances.
-The [AGL compositor](../../06_Component_Documentation/02_agl_compositor/) has
-some additional events which one can use when creating an application
-start-up & switching scheme in different run-times.
-
-Start-up of application is handled entirely by `applaunchd` service while
-activation -- the window which I want to display, but which has never been
-shown, and application switching -- bring forward an application already
-shown/displayed in the past, are operations handled entirely by the
-AGL compositor.
-
-The issue stems from the fact that underneath `applaunchd` can't make any
-guarantees when the application actually started, as it calls into libsystemd
-API to start the specific application systemd unit.
-
-If `StartApplication` can't start the systemd unit, it returns a false
-`status` boolean value and a error message in `StartResponse` message, but if
-the application is indeed started we doesn't really know the *moment* when the
-application is ready to be displayed. Additionally, the AGL compositor
-performed the activation on its own when it detected that a new application
-has been started, but that implicit activation can now be handled outside
-by the desktop run-time/shell client.
-
-*Note: Some of the run-times still rely on the compositor to perform activation
-as this synchronization part between `applaunchd` has not been implemented. The
-plan is to migrate all of remaining run-times to using this approach.*
-
-### Start-up & activation
-
-This means that we require some sort of interaction between `StartApplication`
-method and the events sent by the AGL compositor in order to correctly handle
-start-up & activation of application.
-
-There are couple of ways of achieving that, either using Wayland native calls,
-or using the gRPC proxy interface, which underneath is using the same Wayland
-native calls.
-
-For the first approach, the AGL compositor has an `app_state` Wayland event
-which contains the application ID, and an enum `app_state` that will propagate
-the following application state events:
-
-```
-<enum name="app_state" since="3">
-  <entry name="started" value="0"/>
-  <entry name="terminated" value="1"/>
-  <entry name="activated" value="2"/>
-  <entry name="deactivated" value="3"/>
-</enum>
-```
-
-The `started` event can be used in correlation with the `StartApplication`
-method from `applaunchd` such that upon received the `started` even, it can
-explicitly activate that particular appid in order for the compositor to
-display it. See [AGL compositor](../../06_Component_Documentation/02_agl_compositor/)
-about how activation should be handled.
-
-*Note: These can only be received if by the client shell which binds to the
-agl_shell interface*.
-
-Alternatively, when using the gRPC proxy one can register to receive these
-status events similar to the `applaunchd` events, subscribing to
-`AppStatusState` method from the grpc-proxy helper application, which has the
-following protobuf messages:
-
-```
-message AppStateRequest {
-}
-message AppStateResponse {
-        int32 state = 1;
-        string app_id = 2;
-}
-```
-
-The integer state maps to the `enum app_state` from the Wayland protocol, so
-they are a 1:1 match.
-
-Here's the state diagram for the Qt homescreen implementation of the
-application start-up:
-
-![Application_start](../images/start_and_activation.png)
-
-### Application switching
-
-With the compositor providing application status events, it might seem that the
-`applaunchd`'s, `GetStatusEvents` might be redundant, but in fact it is being
-used to perform application switching. The run-time/shell client would in fact
-subscribe to `GetStatusEvents` and each application wanting to switch to another
-application would basically call `StartApplication`. That would eventually reach
-the run-time/shell-client and have a handler that would ultimately activate the
-application ID.
-
-![Application_switching](../images/application_switching.png)
-
-*Note: In practice, the run-time/shell-client would subscribe to both `applaunchd`
-and to the AGL compositor, either Wayland native events, or using the gPRC-proxy
-helper client, although the diagrams show them partly decoupled*.
diff --git a/docs/04_Developer_Guides/01_Application_Framework/02_Application_Startup_Dbus.md b/docs/04_Developer_Guides/01_Application_Framework/02_Application_Startup_Dbus.md
deleted file mode 100644
index 927b52f..0000000
--- a/docs/04_Developer_Guides/01_Application_Framework/02_Application_Startup_Dbus.md
+++ /dev/null
@@ -1,190 +0,0 @@
----
-title: Application Startup with D-Bus
----
-
-*Note: The that the D-Bus interface is in deprecation phase and for the time
-being only available for application & services that still rely on them. Once
-we migrate everything to gRPC, we will remove D-Bus IPC support. Please see 
-[Application Startup with gRPC](../02_Application_Startup/) for the latest
-information*
-
-# Introduction
-
-At system runtime, it may be necessary for applications to start other applications
-on demand. Such actions can be executed in reaction to a user request, or they may
-be needed to perform a specific task.
-
-In order to do so, running applications and services need an established way of
-discovering installed applications and executing those. The
-[Desktop Entry specification](https://specifications.freedesktop.org/desktop-entry-spec/desktop-entry-spec-latest.html)
-defines how applications can be discovered by using `.desktop` files, but there's no
-simple reference implementation for this function.
-
-In order to provide a language-independent interface for applications and service to
-use, AGL includes `applaunchd`, a user service part of the default session.
-
-*Note: as mentioned [previously](../01_Introduction/), services are managed using `systemd`
-and are therefore not in the scope of this document.*
-
-# Application launcher service
-
-The purpose of `applaunchd` is to enumerate applications available on the system and
-provide a way for other applications to query this list and start those on demand.
-It is also able to notify clients of the startup and termination of applications it
-manages.
-
-To that effect, `applaunchd` provides a D-Bus interface other applications can use
-in order to execute those actions.
-
-*Note: `applaunchd` will only send notifications for applications it started; it isn't
-aware of applications started by other means (`systemd`, direct executable call...),
-and therefore can't send notifications for those.*
-
-## Application discovery
-
-On startup, `applaunchd` inspects all `.desktop` files present under the `applications/`
-subfolder of any element of the `XDG_DATA_DIRS` environment variable, ignoring all entries
-containing either the `NoDisplay=true` or `Hidden=true` lines.
-
-It then looks for the following keys:
-- `Terminal`
-- `DBusActivatable`
-
-If the desktop entry file contains the `Terminal` key set to `true`, then the application
-is marked as a non-graphical one. As such, it won't be included in the applications list
-if the client requests only graphical applications.
-
-If `DBusActivatable` is set to `true`, then the application is marked as D-Bus activated.
-Additionally, `applaunchd` will search for a corresponding D-Bus service file in case this
-line is missing. This is a workaround allowing D-Bus activated applications providing
-an incomplete desktop entry file (i.e missing the `DBusActivatable` key) to be
-identified as such.
-
-### Requirements for D-Bus activation
-
-`applaunchd` will always start D-Bus activatable applications using D-Bus activation
-instead of executing the command line stated in the desktop entry file.
-
-This is handled by calling the `Activate` method of the
-[org.freedesktop.Application](https://specifications.freedesktop.org/desktop-entry-spec/1.1/ar01s07.html)
-interface with an empty argument.
-
-As a consequence, all D-Bus activatable applications **must** implement this D-Bus
-interface.
-
-## Application identifiers
-
-Each application is identified by a unique Application ID. Although this ID can be
-any valid string, it is highly recommended to use the "reverse DNS" convention in order
-to avoid potential name collisions and ease D-Bus integration.
-
-The application ID is set in the desktop entry file itself for
-[graphical applications](/04_Developer_Guides/03_Creating_a_New_Application_Dbus/#graphical-applications):
-it is the value of the `StartupWMClass` field, which must be identical to the `app-id`
-advertised through the Wayland XDG toplevel protocol. In case this field is missing
-(as is usually the case for non-graphical application), the application ID will be the
-desktop entry file name, stripped from its `.desktop` extension.
-
-## D-Bus interface
-
-The `applaunchd` D-Bus interface is named `org.automotivelinux.AppLaunch`. The object
-path for `applaunchd` is `/org/automotivelinux/AppLaunch`. The interface provides methods
-for the following actions:
-- retrieve the list of available applications; the client can choose to retrieve all
-  available applications, or only those suitable for a graphical environment
-- request an application to be started
-
-Moreover, signals are available for clients to be notified when an application has
-successfully started or its execution terminated.
-
-### Applications list
-
-The `listApplications` method allows clients to retrieve the list of available applications.
-It takes one boolean argument named `graphical`:
-- if set to `true`, only applications suitable for graphical environments are returned
-- otherwise, the list contains all applications
-
-This method returns an array of variants (type `av`), each element being a structure made up
-of 3 strings (type `(sss)`):
-- the application ID
-- the application's displayed name
-- the full path to the application icon file (or an empty string if no icon was specified in
-  the application's desktop entry file)
-
-### Application startup request
-
-Applications can be started by using the `start` method, passing the corresponding application
-ID as the only argument. This method doesn't return any data.
-
-If the application is already running, `applaunchd` won't start another instance, but instead
-emit a `started` signal to notify clients the application is ready.
-
-### Status notifications
-
-The `org.automotivelinux.AppLaunch` interface provides 2 signals clients can connect to:
-- `started` indicates an application has started
-    - for D-Bus activated applications, it is emitted upon successful completion of the
-      call to the `Activate` method of the `org.freedesktop.Application` interface
-    - for other applications, this signal is emitted as soon as the child process has been
-      successfully created
-- `terminated` is emitted when an application quits
-
-Both signals have an additional argument named `appid`, containing the ID of the application
-affected by the event.
-
-As mentioned above, the `started` signal is also emitted if `applaunchd` receives a request to
-start an already running application. This can be useful, for example, when switching between
-graphical applications:
-- the application switcher doesn't need to track the state of each application; instead, it can
-  simply send a `start` request to `applaunchd` every time the user requests to switch to another
-  application
-- the desktop environment then receives the `started` signal, indicating it should activate the
-  window with the corresponding `app-id`
-
-## Testing
-
-`applaunchd` can be manually tested using the `gdbus` command-line tool:
-
-1. Query the application list (graphical applications only):
-
-```
-$ gdbus call --session --dest "org.automotivelinux.AppLaunch" \
-                       --object-path "/org/automotivelinux/AppLaunch" \
-                       --method "org.automotivelinux.AppLaunch.listApplications" \
-                       true
-```
-
-This command will output something similar to what follows:
-
-```
-([<('navigation', 'Navigation', '/usr/share/icons/hicolor/scalable/navigation.svg')>,
- <('settings', 'Settings', '/usr/share/icons/hicolor/scalable/settings.svg')>,
- <('dashboard', 'Dashboard', '/usr/share/icons/hicolor/scalable/dashboard.svg')>,
- <('hvac', 'HVAC', '/usr/share/icons/hicolor/scalable/hvac.svg')>,
- <('org.freedesktop.weston.wayland-terminal', 'Weston Terminal', '/usr/share/icons/Adwaita/scalable/apps/utilities-terminal-symbolic.svg')>],)
-```
-
-2. Request startup of the `org.freedesktop.weston.wayland-terminal` application:
-
-```
-$ gdbus call --session --dest "org.automotivelinux.AppLaunch" \
-                       --object-path "/org/automotivelinux/AppLaunch" \
-                       --method "org.automotivelinux.AppLaunch.start" \
-                       "org.freedesktop.weston.wayland-terminal"
-```
-
-3. Monitor signals emitted by `applaunchd`:
-
-```
-$ gdbus monitor --session --dest "org.automotivelinux.AppLaunch"
-```
-
-This results in the following output when starting, then exiting, the
-`org.freedesktop.weston.wayland-terminal` application:
-
-```
-Monitoring signals from all objects owned by org.automotivelinux.AppLaunch
-The name org.automotivelinux.AppLaunch is owned by :1.4
-/org/automotivelinux/AppLaunch: org.automotivelinux.AppLaunch.started ('org.freedesktop.weston.wayland-terminal',)
-/org/automotivelinux/AppLaunch: org.automotivelinux.AppLaunch.terminated ('org.freedesktop.weston.wayland-terminal',)
-```
diff --git a/docs/04_Developer_Guides/01_Application_Framework/03_Creating_a_New_Service.md b/docs/04_Developer_Guides/01_Application_Framework/03_Creating_a_New_Service.md
deleted file mode 100644
index 22e98ea..0000000
--- a/docs/04_Developer_Guides/01_Application_Framework/03_Creating_a_New_Service.md
+++ /dev/null
@@ -1,151 +0,0 @@
----
-title: Creating a New Service
----
-
-Services are software running in the background and providing, as their name suggests,
-various services to other software: access to specific system hardware, connectivity
-management, and network servers. Services can be split into 2 categories:
-
-- **System services:** those usually run as a privileged user and make use of shared system
-  resources which they should have exclusive access to
-
-- **User services:** such services run as part of an unprivileged user's session and can
-  only be called by said user
-
-# Basic requirements
-
-The only mandatory requirement is that service packages provide a `.service` file
-so they can be properly managed by `systemd`. This file must be installed to a specific
-location, determined by the service type (system or user):
-
-- `/usr/lib/systemd/system/` for system services
-
-- `/usr/lib/systemd/user/` for user services
-
-Below is an example of a simple user service, running in a graphical session and
-therefore requiring a compositor to be already running before the service starts:
-
-```
-[Unit]
-Requires=agl-compositor.service
-After=agl-compositor.service
-
-[Service]
-Type=simple
-ExecStart=/usr/bin/homescreen
-Restart=on-failure
-
-[Install]
-WantedBy=agl-session.target
-```
-
-The `WantedBy=agl-session.target` indicates the service is part of the default AGL
-user session, as mentioned in the [Application Framework](../01_Application_Framework/01_Introduction/#user-session-management)
-documentation.
-
-The `Restart=on-failure` directive ensures the service will be automatically
-restarted by `systemd` in case it crashes.
-
-More details about `systemd` service files can be found in the
-[systemd documentation](https://www.freedesktop.org/software/systemd/man/systemd.service.html).
-
-# D-Bus activation
-
-Services can also provide a D-Bus interface. In this case, they need not be started
-on system boot (or user session startup in the case of user services) but can be
-automatically started only when a client sends a request to the D-Bus name the service
-registers.
-
-D-Bus activated services must name their `systemd` service file `dbus-NAME.service`
-where `NAME` is the D-Bus name registered by the service. This file must include the
-following lines:
-
-```
-[Service]
-Type=dbus
-BusName=NAME
-ExecStart=/path/to/executable
-```
-
-In addition, they must provide a D-Bus service file named `NAME.service` and installed
-to one of the following locations:
-
-- `/usr/share/dbus-1/system-services` for system services
-
-- `/usr/share/dbus-1/services` for user services
-
-The contents of the D-Bus service file must be the following:
-
-```
-[D-BUS Service]
-Name=NAME
-Exec=/path/to/executable
-SystemdService=dbus-NAME.service
-```
-
-This ensures the service can be safely activated through D-Bus and no conflict will occur
-between `systemd` and the D-Bus daemon.
-
-More details about D-Bus activation can be found in the
-[D-Bus specification](https://dbus.freedesktop.org/doc/dbus-specification.html#message-bus-starting-services),
-under the "Message Bus Starting Services (Activation)" section.
-
-# Services startup
-
-For D-Bus activated services, no additional action is required as those will be automatically
-started whenever needed. Other services, however, need a few more steps in order to be
-executed on system or session startup.
-
-## System services
-
-System services can take advantage of the Yocto `systemd` class which automates the process of
-enabling such services.
-
-1\. Ensure the recipe inherits from the `systemd` class:
-
-```
-inherit systemd
-```
-
-2\. Declare the system services that needs to be enabled on boot:
-
-```
-SYSTEMD_SERVICE:${PN} = "NAME.service"
-```
-
-3\. Ensure the `FILES` variable includes the systemd service directory the corresponding
-file will be installed to:
-
-```
-FILES:${PN} = "\
-    ...
-    ${systemd_system_unitdir}/* \
-"
-```
-
-## User services
-
-The `systemd` class doesn't provide an equivalent mechanism for user services. This must
-therefore be done manually as part of the package's install process.
-
-1\. Make the service a part of the user session:
-
-```
-do_install:append() {
-    install -d ${D}${systemd_user_unitdir}/agl-session.target.wants
-    ln -s ../NAME.service ${D}${systemd_user_unitdir}/agl-session.target.wants/NAME.service
-}
-```
-
-This ensures `agl-session.target` depends on `NAME.service`, the latter being therefore
-automatically started on session creation.
-
-2\. Ensure the `FILES` variable includes the systemd service directory the corresponding
-file will be installed to:
-
-```
-FILES:${PN} = "\
-    ...
-    ${systemd_user_unitdir}/* \
-"
-```
diff --git a/docs/04_Developer_Guides/01_Application_Framework/04_Creating_a_New_Application_Dbus.md b/docs/04_Developer_Guides/01_Application_Framework/04_Creating_a_New_Application_Dbus.md
deleted file mode 100644
index edee0dc..0000000
--- a/docs/04_Developer_Guides/01_Application_Framework/04_Creating_a_New_Application_Dbus.md
+++ /dev/null
@@ -1,139 +0,0 @@
----
-title: Creating a New Application with D-bus activation
----
-
-*Note: The that the D-Bus interface is in deprecation phase and for the time
-being only available for application & services that still rely on them. Once
-we migrate everything to gRPC, we will remove D-Bus IPC support.*
-
-Applications are:
-
--  Software designed to perform a specific task during a limited amount of time.
--  Graphical interface allowing user to interact with.
-
-Applications are executed by `applaunchd`, the AGL
-[application launcher service](../01_Application_Framework/02_Application_Startup_Dbus/).
-
-# Basic requirements
-
-In order to be enumerated by `applaunchd`, applications must provide the a `.desktop` file, as
-defined by the [Desktop Entry specification](https://specifications.freedesktop.org/desktop-entry-spec/desktop-entry-spec-latest.html).
-
-The desktop entry file should be installed to `/usr/share/applications` (or the `applications`
-sub-directory of any entry present in the `XDG_DATA_DIRS` environment variable) and have a
-meaningful name. It is considered good practice to use reverse-DNS notation for the desktop
-entry file name, following the recommendations of the [D-Bus specification](https://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-names):
-- this avoids potential name collisions with other desktop entry files
-- it makes it easier to enable [D-Bus activation](#d-bus-activation) during the application
-  development cycle if needed
-- for [graphical applications](#graphical-applications), it ensures the chosen Wayland `app-id`
-  will be unique
-
-Such a file must contain at least the following keys:
-- `Type`: desktop entry type, must be set to `Application`
-- `Name`: application name, as it should be displayed in menus and application launchers
-- `Exec`: full path to the main executable
-
-Below is an example of a minimal desktop entry file:
-
-```
-[Desktop Entry]
-Type=Application
-Name=Example Application
-Exec=/usr/bin/example-app
-```
-
-Graphical applications must also provide an `Icon` entry pointing to the application icon.
-The value for this entry must either be the full path to the icon's file or, for icons part
-of an existing [icon theme](https://specifications.freedesktop.org/icon-theme-spec/icon-theme-spec-latest.html),
-the name of an element of this theme.
-
-In addition, a number of optional fields can be used to change how `applaunchd` will consider the
-application:
-- `Version`: version of the Desktop Entry Specification the file conforms to, must be `1.5`
-- `Hidden`: boolean value, if `true` the application is always ignored by `applaunchd` and
-  won't be listed nor executed
-- `Terminal`: boolean value, if `true` the application is excluded when requesting the list of
-  graphical applications from `applaunchd`
-- `DBusActivatable`: boolean value, must be `true` for [D-Bus activated applications](#d-bus-activation)
-- `Implements`: list of D-Bus interfaces the application implements, only used for D-Bus activated
-  applications.
-
-Finally, graphical applications may also define the `StartupWMClass` key in some cases. Please
-refer to the [graphical applications](#graphical-applications) section for more information.
-
-# D-Bus activation
-
-Similarly to [services](../02_Creating_a_New_Service/#d-bus-activation), applications can
-also be activated through D-Bus.
-
-Such applications must name their `.desktop` file after the D-Bus name they register. In addition,
-this file must contain the following entries:
-
-```
-DBusActivatable=true
-Implements=IFACE1;IFACE2;...
-```
-
-Where `IFACEn` are the names of the D-Bus interfaces the application implements.
-
-In addition, they must provide a D-Bus service file named `NAME.service` and installed
-to `/usr/share/dbus-1/services`.
-
-The contents of the D-Bus service file must be the following:
-
-```
-[D-BUS Service]
-Name=NAME
-Exec=/path/to/executable
-```
-
-For example, an application registering the `org.automotivelinux.Example` D-Bus name
-and implementing the `org.automotivelinux.Example.Search1` and `org.automotivelinux.Example.Execute1`
-interfaces would provide the following files:
-
-* Desktop entry (`/usr/share/applications/org.automotivelinux.Example.desktop`):
-
-```
-[Desktop Entry]
-Type=Application
-Version=1.5
-Name=Example Application
-Exec=/usr/bin/example-app
-Icon=example-icon
-Terminal=false
-DBusActivatable=true
-Implements=org.automotivelinux.Example.Search1;org.automotivelinux.Example.Execute1
-```
-
-* D-Bus service file (`/usr/share/dbus-1/services/org.automotivelinux.Example.service`):
-
-```
-[D-BUS Service]
-Name=org.automotivelinux.Example
-Exec=/usr/bin/example-app
-```
-
-*Note: in addition to their own D-Bus interface, D-Bus activated applications must also
-implement the `org.freedesktop.Application` interface as defined in the
-[Desktop Entry specification](https://specifications.freedesktop.org/desktop-entry-spec/1.1/ar01s07.html).*
-
-# Graphical applications
-
-In addition, graphical applications need to comply with a few more requirements:
-
-1\. Each application must set a Wayland application ID appropriately as soon as its main window
-is created.
-
-2\. The `app-id` must be specified in the desktop entry file by adding the following line:
-
-```
-StartupWMClass=APP_ID
-```
-
-3\. The desktop entry file must be named `APP_ID.desktop`.
-
-Doing so will ensure other software can associate the actual `app-id` to the proper application.
-
-*Note: application ID's are set using the [XDG toplevel](https://wayland-book.com/xdg-shell-basics/xdg-toplevel.html)
-Wayland interface.*
diff --git a/docs/04_Developer_Guides/images/application_switching.msc b/docs/04_Developer_Guides/images/application_switching.msc
deleted file mode 100755
index ceeab7c..0000000
--- a/docs/04_Developer_Guides/images/application_switching.msc
+++ /dev/null
@@ -1,29 +0,0 @@
-#!/usr/bin/mscgen -Tpng
-
-msc {
-       hscale="1.5";
-
-       u [label = "touch/pointer event" ],
-       l [label = "launcher app" ],
-       s [label = "runtime/shell-client"],
-       a [label = "applaunchd" ],
-       g [label = "gRPC-proxy" ],
-       c [label = "compositor" ],
-       d [label = "libsystemd"];
-
-       |||;
-
-       --- [label = "initial phase - subscribe for signal/status events, assume app_id already started" ];
-
-       s >> a [label = "subscribe for applaunchd GetStatusEvents"];
-
-       --- [label = "handling of application switching" ];
-
-       u => l [label = "tapShortCut(appid)" ];
-       l => a [label = "StartApplication(appid)"];
-       a => d [label = "start application's systemd unit"];
-       d => a [label = "return status from starting systemd unit"];
-       a => s [label = "StartResponse(status = TRUE)"];
-       a => s [label = "StatusResponse(app_id, 'started')"];
-       s => c [label = "activate_app(app_id)"];
-}
diff --git a/docs/04_Developer_Guides/images/application_switching.png b/docs/04_Developer_Guides/images/application_switching.png
deleted file mode 100644
index 0b5584a..0000000
--- a/docs/04_Developer_Guides/images/application_switching.png
+++ /dev/null
diff --git a/docs/04_Developer_Guides/images/start_and_activation.msc b/docs/04_Developer_Guides/images/start_and_activation.msc
deleted file mode 100755
index d835f8b..0000000
--- a/docs/04_Developer_Guides/images/start_and_activation.msc
+++ /dev/null
@@ -1,30 +0,0 @@
-#!/usr/bin/mscgen -Tpng
-
-msc {
-       hscale="1.5";
-
-       u [label = "touch/pointer event" ],
-       s [label = "runtime/shell-client"],
-       a [label = "applaunchd" ],
-       g [label = "gRPC-proxy" ],
-       c [label = "compositor" ],
-       d [label = "libsystemd"];
-
-       |||;
-
-       --- [label = "initial phase - subscribe for signal/status events" ];
-
-       s >> g [label = "subscribe for AGL compositor AppStatusState"];
-       g >> c [label = "listen for app_state Wayland events"];
-
-       --- [label = "handling start-up & activation" ];
-
-       u => s [label = "tapShortCut(appid)" ];
-       s => a [label = "StartApplication(appid)"];
-       a => d [label = "start application's systemd unit"];
-       d => a [label = "return status from starting systemd unit"];
-       a => s [label = "StartResponse(status = TRUE)"];
-       c => g [label = "app_state(app_state = APP_STARTED)"];
-       g => s [label = "AppStatusResponse(app_id, APP_STARTED)"];
-       s => c [label = "activate_app(app_id)"];
-}
diff --git a/docs/04_Developer_Guides/images/start_and_activation.png b/docs/04_Developer_Guides/images/start_and_activation.png
deleted file mode 100644
index 593fc0e..0000000
--- a/docs/04_Developer_Guides/images/start_and_activation.png
+++ /dev/null