+++ /dev/null
----
-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.md) 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.md), 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_Creating_a_New_Application_Dbus.md#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',)
-```
Code Review / AGL / documentation.git / blobdiff