Volume Control Plugin

Version: 1.0

Status:

VolumeControl plugin for Thunder framework.

Table of Contents

• Introduction
• Description
• Configuration
• Interfaces
• Methods
• Properties
• Notifications

Introduction

Scope

This document describes purpose and functionality of the VolumeControl plugin. It includes detailed specification about its configuration, methods and properties as well as sent notifications.

Case Sensitivity

All identifiers of the interfaces described in this document are case-sensitive. Thus, unless stated otherwise, all keywords, entities, properties, relations and actions should be treated as such.

Acronyms, Abbreviations and Terms

The table below provides and overview of acronyms used in this document and their definitions.

Acronym	Description
API	Application Programming Interface
HTTP	Hypertext Transfer Protocol
JSON	JavaScript Object Notation; a data interchange format
JSON-RPC	A remote procedure call protocol encoded in JSON

The table below provides and overview of terms and abbreviations used in this document and their definitions.

Term	Description
callsign	The name given to an instance of a plugin. One plugin can be instantiated multiple times, but each instance the instance name, callsign, must be unique.

References

Ref ID	Description
HTTP	HTTP specification
JSON-RPC	JSON-RPC 2.0 specification
JSON	JSON specification
Thunder	Thunder API Reference

Description

The Volume Control plugin allows to manage system's audio volume.

The plugin is designed to be loaded and executed within the Thunder framework. For more information about the framework refer to [Thunder].

Configuration

The table below lists configuration options of the plugin.

Name	Type	M/O	Description
callsign	string	mandatory	Plugin instance name (default: VolumeControl)
classname	string	mandatory	Class name: VolumeControl
locator	string	mandatory	Library name: libWPEVolumeControl.so
startmode	string	mandatory	Determines in which state the plugin should be moved to at startup of the framework

Interfaces

This plugin implements the following interfaces:

• IVolumeControl (IVolumeControl.h) (version 1.0.0) (uncompliant-extended format)

  This interface uses legacy lowercase naming convention. With the next major release the naming convention will change to camelCase.

Methods

The following methods are provided by the VolumeControl plugin:

Built-in methods:

Method	Description
versions	Retrieves a list of JSON-RPC interfaces offered by this service
exists	Checks if a JSON-RPC method or property exists
register	Registers for an asynchronous JSON-RPC notification
unregister	Unregisters from an asynchronous JSON-RPC notification

versions ^method

Retrieves a list of JSON-RPC interfaces offered by this service.

Parameters

This method takes no parameters.

Result

Name	Type	M/O	Description
result	array	mandatory	A list ofsinterfaces with their version numbers Array length must be at most 255 elements.
result[#]	object	mandatory	...
result[#].name	string	mandatory	Name of the interface
result[#].major	integer	mandatory	Major part of version number
result[#].minor	integer	mandatory	Minor part of version number
result[#].patch	integer	mandatory	Patch part of version version number

Example

Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "VolumeControl.1.versions"
}

Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": [
    {
      "name": "JMyInterface",
      "major": 1,
      "minor": 0,
      "patch": 0
    }
  ]
}

exists ^method

Checks if a JSON-RPC method or property exists.

Description

This method will return True for the following methods/properties: muted, volume, versions, exists, register, unregister.

Parameters

Name	Type	M/O	Description
params	object	mandatory	...
params.method	string	mandatory	Name of the method or property to look up

Result

Name	Type	M/O	Description
result	boolean	mandatory	Denotes if the method exists or not

Example

Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "VolumeControl.1.exists",
  "params": {
    "method": "methodName"
  }
}

Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": false
}

register ^method

Registers for an asynchronous JSON-RPC notification.

Description

This method supports the following event names: volume, muted.

Parameters

Name	Type	M/O	Description
params	object	mandatory	...
params.event	string	mandatory	Name of the notification to register for
params.id	string	mandatory	Client identifier

Result

Name	Type	M/O	Description
result	null	mandatory	Always null

Errors

Message	Description
ERROR_FAILED_REGISTERED	Failed to register for the notification (e.g. already registered)

Example

Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "VolumeControl.1.register",
  "params": {
    "event": "eventName",
    "id": "myapp"
  }
}

Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": null
}

unregister ^method

Unregisters from an asynchronous JSON-RPC notification.

Description

This method supports the following event names: volume, muted.

Parameters

Name	Type	M/O	Description
params	object	mandatory	...
params.event	string	mandatory	Name of the notification to register for
params.id	string	mandatory	Client identifier

Result

Name	Type	M/O	Description
result	null	mandatory	Always null

Errors

Message	Description
ERROR_FAILED_UNREGISTERED	Failed to unregister from the notification (e.g. not yet registered)

Example

Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "VolumeControl.1.unregister",
  "params": {
    "event": "eventName",
    "id": "myapp"
  }
}

Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": null
}

Properties

The following properties are provided by the VolumeControl plugin:

VolumeControl interface properties:

Property	R/W	Description
muted	read/write	Audio mute state
volume	read/write	Audio volume level

muted ^property

Provides access to the audio mute state.

Value

Name	Type	M/O	Description
(property)	boolean	mandatory	Mute state (true: muted, false: un-muted)

Name	Type	M/O	Description
(property)	boolean	mandatory	Mute state (true: muted, false: un-muted)

Errors

Message	Description
ERROR_GENERAL	Failed to set/retrieve muting state

Example

Get Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "VolumeControl.1.muted"
}

Get Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": false
}

Set Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "VolumeControl.1.muted",
  "params": false
}

Set Response

{
    "jsonrpc": "2.0",
    "id": 42,
    "result": "null"
}

volume ^property

Provides access to the audio volume level.

Value

Name	Type	M/O	Description
(property)	integer	mandatory	Volume level in percent

Name	Type	M/O	Description
(property)	integer	mandatory	Volume level in percent

Errors

Message	Description
ERROR_GENERAL	Failed to set/retrieve audio volume

Example

Get Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "VolumeControl.1.volume"
}

Get Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": 0
}

Set Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "VolumeControl.1.volume",
  "params": 100
}

Set Response

{
    "jsonrpc": "2.0",
    "id": 42,
    "result": "null"
}

Notifications

Notifications are autonomous events triggered by the internals of the implementation and broadcasted via JSON-RPC to all registered observers. Refer to [Thunder] for information on how to register for a notification.

The following events are provided by the VolumeControl plugin:

VolumeControl interface events:

Notification	Description
volume	Signals volume change
muted	Signals mute state change

volume ^notification

Signals volume change.

Notification Parameters

Name	Type	M/O	Description
params	object	mandatory	...
params.volume	integer	mandatory	New bolume level in percent

Example

Registration

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "VolumeControl.1.register",
  "params": {
    "event": "volume",
    "id": "myid"
  }
}

Notification

{
  "jsonrpc": "2.0",
  "method": "myid.volume",
  "params": {
    "volume": 100
  }
}

The client ID parameter is passed within the notification designator, i.e. <client-id>.volume.

muted ^notification

Signals mute state change.

Notification Parameters

Name	Type	M/O	Description
params	object	mandatory	...
params.muted	boolean	mandatory	New mute state (true: muted, false: un-muted)

Example

Registration

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "VolumeControl.1.register",
  "params": {
    "event": "muted",
    "id": "myid"
  }
}

Notification

{
  "jsonrpc": "2.0",
  "method": "myid.muted",
  "params": {
    "muted": false
  }
}

The client ID parameter is passed within the notification designator, i.e. <client-id>.muted.