Merge pull request #454 from ChartIQ/ClarifyAutoBroadcastOnJoin

Clarify existing behavior of joinChannel and addIntentListener when joining a channel

docs/api/ref/DesktopAgent.md

@@ -55,8 +55,9 @@ addContextListener(contextType: string | null, handler: ContextHandler): Listene
  */
 addContextListener(handler: ContextHandler): Listener;
 ```
-Adds a listener for incoming context broadcast from the Desktop Agent. If the consumer is only interested in
-a context of a particular type, they can use the relevant overload that allows the type to be specified.
+Adds a listener for incoming context broadcasts from the Desktop Agent. If the consumer is only interested in a context of a particular type, they can specify that type. If the consumer is able to receive context of any type or will inspect types received, then they can pass `null` as the `contextType` parameter to receive all context types. 
+
+Context broadcasts are only received from apps that are joined to the same channel as the listening application, hence, if the application is not currently joined to a channel no broadcasts will be received. If this function is called after the app has already joined a channel and the channel already contains context that would be passed to the context listener, then it will be called immediately with that context.
 
 #### Examples
 ```js
@@ -127,7 +128,7 @@ findIntent(intent: string, context?: Context): Promise<AppIntent>;
 
 Find out more information about a particular intent by passing its name, and optionally its context.
 
-_findIntent_ is effectively granting programmatic access to the Desktop Agent's resolver.
+`findIntent` is effectively granting programmatic access to the Desktop Agent's resolver.
 It returns a promise resolving to the intent, its metadata and metadata about the apps that are registered to handle it.
 This can be used to raise the intent against a specific app.
 
@@ -157,7 +158,7 @@ findIntentsByContext(context: Context): Promise<Array<AppIntent>>;
 ```
 
 Find all the avalable intents for a particular context.
-_findIntentsByContext_ is effectively granting programmatic access to the Desktop Agent's resolver.
+`findIntentsByContext` is effectively granting programmatic access to the Desktop Agent's resolver.
 A promise resolving to all the intents, their metadata and metadata about the apps that registered as handlers is returned, based on the context types the intents have registered.
 
  If the resolution fails, the promise will return an `Error` with a string from the [`ResolveError`](ResolveError) enumeration.
@@ -287,10 +288,13 @@ joinChannel(channelId: string) : Promise<void>;
 ```
 
 Joins the app to the specified channel.
-If an app is joined to a channel, all _fdc3.broadcast_ calls will go to the channel, and all listeners assigned via _fdc3.addContextListener_ will listen on the channel.
+If an app is joined to a channel, all `fdc3.broadcast` calls will go to the channel, and all listeners assigned via `fdc3.addContextListener` will listen on the channel. 
+
+If the channel already contains context that would be passed to context listeners added via `fdc3.addContextListener` then those listeners will be called immediately with that context.
+
 An app can only be joined to one channel at a time.
-Rejects with error if the channel is unavailable or the join request is denied.
- `Error` with a string from the [`ChannelError`](Errors#channelerror) enumeration.
+
+Rejects with an error if the channel is unavailable or the join request is denied. The error string will be drawn from the [`ChannelError`](Errors#channelerror) enumeration.
 
 #### Examples
 
@@ -315,7 +319,7 @@ fdc3.joinChannel(selectedChannel.id);
 leaveCurrentChannel() : Promise<void>;
 ```
 
-Removes the app from any channel membership.  Context broadcast and listening through the top-level `fdc3.broadcast` and `fdc3.addContextListener` will be in a no-op when the app is not on a channel.
+Removes the app from any channel membership.  Context broadcast and listening through the top-level `fdc3.broadcast` and `fdc3.addContextListener` will be a no-op when the app is not joined to a channel.
 
 
 #### Examples
@@ -325,7 +329,7 @@ Removes the app from any channel membership.  Context broadcast and listening th
 const fdc3Listener = fdc3.addContextListener(null, context => {});
 
 await fdc3.leaveCurrentChannel();
-//the fdc3Listener will now cease recieving context
+//the fdc3Listener will now cease receiving context
 
 //listening on a specific channel though, will continue to work
 redChannel.addContextListener(null, channelListener);

docs/api/spec.md

@@ -221,9 +221,11 @@ There are two types of channels, which are functionally identical, but have diff
 
 
 ### Joining Channels
-Apps can join channels.  An app can only be joined to one channel at a time.  When an app joins a channel it will automatically recieve the current context for that channel.
+Apps can join channels.  An app can only be joined to one channel at a time.  
 
-When an app is joined to a channel, calls to `fdc3.broadcast` and listeners added through `fdc3.addContextListener` will be routed to that channel. If an app is not joined to a channel `fdc3.broadcast` will be a no-op and handler functions added with `fdc3.addContextListener` will not receive any broadcasts. However, apps can still choose to listen and broadcast to specific channels via the methods on the `Channel` class.
+When an app is joined to a channel, calls to `fdc3.broadcast` will be routed to that channel and listeners added through `fdc3.addContextListener` will receive context broadcasts from other apps also joined to that channel. If an app is not joined to a channel `fdc3.broadcast` will be a no-op and handler functions added with `fdc3.addContextListener` will not receive any broadcasts. However, apps can still choose to listen and broadcast to specific channels via the methods on the `Channel` class.
+
+When an app joins a channel, or adds a context listener when already joined to a channel, it will automatically receive the current context for that channel.
 
 It is possible that a call to join a channel could be rejected.  If for example, the desktop agent wanted to implement controls around what data apps can access.
 

src/api/DesktopAgent.ts

@@ -32,11 +32,11 @@ export interface DesktopAgent {
    *
    *  ```javascript
    *     //no context and string as target
-   *     agent.open('myApp');
+   *     fdc3.open('myApp');
    *     //no context and AppMetadata object as target
-   *     agent.open({name: 'myApp', title: 'The title for the application myApp.', description: '...'});
+   *     fdc3.open({name: 'myApp', title: 'The title for the application myApp.', description: '...'});
    *     //with context
-   *     agent.open('myApp', context);
+   *     fdc3.open('myApp', context);
    * ```
    */
   open(app: TargetApp, context?: Context): Promise<void>;
@@ -52,7 +52,7 @@ export interface DesktopAgent {
    *
    * ```javascript
    * // I know 'StartChat' exists as a concept, and want to know more about it ...
-   * const appIntent = await agent.findIntent("StartChat");
+   * const appIntent = await fdc3.findIntent("StartChat");
    *
    * // returns a single AppIntent:
    * // {
@@ -61,7 +61,7 @@ export interface DesktopAgent {
    * // }
    *
    * // raise the intent against a particular app
-   * await agent.raiseIntent(appIntent.intent.name, context, appIntent.apps[0].name);
+   * await fdc3.raiseIntent(appIntent.intent.name, context, appIntent.apps[0].name);
    * ```
    */
   findIntent(intent: string, context?: Context): Promise<AppIntent>;
@@ -77,7 +77,7 @@ export interface DesktopAgent {
    *
    * ```javascript
    * // I have a context object, and I want to know what I can do with it, hence, I look for for intents...
-   * const appIntents = await agent.findIntentsByContext(context);
+   * const appIntents = await fdc3.findIntentsByContext(context);
    *
    * // returns for example:
    * // [{
@@ -96,19 +96,25 @@ export interface DesktopAgent {
    * const selectedApp = startChat.apps[0];
    *
    * // raise the intent, passing the given context, targeting the app
-   * await agent.raiseIntent(startChat.intent.name, context, selectedApp.name);
+   * await fdc3.raiseIntent(startChat.intent.name, context, selectedApp.name);
    * ```
    */
   findIntentsByContext(context: Context): Promise<Array<AppIntent>>;
 
   /**
-   * Publishes context to other apps on the desktop.
-   *
-   * DesktopAgent implementations should ensure that context messages broadcast to a channel
-   * by an application joined to it should not be delivered back to that same application.
+   * Publishes context to other apps on the desktop.  Calling `broadcast` at the `DesktopAgent` scope will push the context to whatever `Channel` the app is joined to.  If the app is not currently joined to a channel, calling `fdc3.broadcast` will have no effect.  Apps can still directly broadcast and listen to context on any channel via the methods on the `Channel` class.
+   * 
+   * DesktopAgent implementations should ensure that context messages broadcast to a channel by an application joined to it should not be delivered back to that same application.
    *
    * ```javascript
-   *  agent.broadcast(context);
+   * const instrument = {
+   *   type: 'fdc3.instrument',
+   *   id: {
+   *     ticker: 'AAPL'
+   *   }
+   * };
+
+   * fdc3.broadcast(context);
    * ```
    */
   broadcast(context: Context): void;
@@ -148,7 +154,14 @@ export interface DesktopAgent {
   addContextListener(handler: ContextHandler): Listener;
 
   /**
-   * Adds a listener for the broadcast of a specific type of context object.
+   * Adds a listener for incoming context broadcasts from the Desktop Agent. If the consumer is only interested in a context of a particular type, they can they can specify that type. If the consumer is able to receive context of any type or will inspect types received, then they can pass `null` as the `contextType` parameter to receive all context types.
+   * Context broadcasts are only received from apps that are joined to the same channel as the listening application, hence, if the application is not currently joined to a channel no broadcasts will be received. If this function is called after the app has already joined a channel and the channel already contains context that would be passed to the context listener, then it will be called immediately with that context.
+   * ```javascript
+   * // any context
+   * const listener = fdc3.addContextListener(null, context => { ... });
+   * // listener for a specific type
+   * const contactListener = fdc3.addContextListener('fdc3.contact', contact => { ... });
+   * ```
    */
   addContextListener(contextType: string | null, handler: ContextHandler): Listener;
 
@@ -159,34 +172,45 @@ export interface DesktopAgent {
 
   /**
    * Joins the app to the specified channel.
+   * If an app is joined to a channel, all `fdc3.broadcast` calls will go to the channel, and all listeners assigned via `fdc3.addContextListener` will listen on the channel.
+   * If the channel already contains context that would be passed to context listeners assed via `fdc3.addContextListener` then those listeners will be called immediately with that context.
    * An app can only be joined to one channel at a time.
-   * Rejects with error if the channel is unavailable or the join request is denied.
-   * `Error` with a string from the `ChannelError` enumeration.
+   * Rejects with an error if the channel is unavailable or the join request is denied. The error string will be drawn from the `ChannelError` enumeration.
+   * ```javascript
+   *   // get all system channels
+   *   const channels = await fdc3.getSystemChannels();
+   *   // create UI to pick from the system channels
+   *   // join the channel on selection
+   *   fdc3.joinChannel(selectedChannel.id);
+   *  ```
    */
   joinChannel(channelId: string): Promise<void>;
 
   /**
    * Returns a channel with the given identity. Either stands up a new channel or returns an existing channel.
-   *
    * It is up to applications to manage how to share knowledge of these custom channels across windows and to manage
    * channel ownership and lifecycle.
-   *
    * `Error` with a string from the `ChannelError` enumeration.
    */
   getOrCreateChannel(channelId: string): Promise<Channel>;
 
   /**
    * Returns the `Channel` object for the current channel membership.
-   *
    * Returns `null` if the app is not joined to a channel.
    */
   getCurrentChannel(): Promise<Channel | null>;
 
   /**
    * Removes the app from any channel membership.
-   *
-   * Context broadcast and listening through the top-level `fdc3.broadcast` and `fdc3.addContextListener` will be
-   * in a no-op when the app is not on a channel.
+   * Context broadcast and listening through the top-level `fdc3.broadcast` and `fdc3.addContextListener` will be a no-op when the app is not on a channel.
+   * ```javascript
+   * //desktop-agent scope context listener
+   * const fdc3Listener = fdc3.addContextListener(null, context => {});
+   * await fdc3.leaveCurrentChannel();
+   * //the fdc3Listener will now cease receiving context
+   * //listening on a specific channel though, will continue to work
+   * redChannel.addContextListener(null, channelListener);
+   * ```
    */
   leaveCurrentChannel(): Promise<void>;