haiku/docs/user/midi2/midiroster.dox

/*!
\class BMidiRoster MidiRoster.h
\brief Interface to the system-wide Midi Roster

BMidiRoster allows you to find available MIDI consumer and producer objects. 
You can locate these objects using the iterative NextEndpoint(), 
NextProducer(), and NextConsumer() methods or by requesting notification 
messages to be sent with StartWatching(). Notification messages may contain 
object IDs which can be resolved using the FindEndpoint(), FindProducer(), and 
FindConsumer() methods.

The constructor and destructor of BMidiRoster are private, which means that you 
cannot create or delete your own BMidiRoster objects. Every application can 
have only one instance of BMidiRoster, which is automatically created the very 
first time you use a Midi Kit function. 

You can call BMidiRoster's functions like this:

\code
producer = BMidiRoster::FindProducer(someID);
\endcode

Or using the slightly more annoying:

\code
BMidiRoster* roster = BMidiRoster::MidiRoster();
if (roster != NULL)
{
    producer = roster->FindProducer(someID);
}
\endcode
*/

/*!
\fn BMidiEndpoint* BMidiRoster::NextEndpoint(int32* id)
\brief Returns the next endpoint from the roster

The "next endpoint" means: the endpoint with the ID that follows id. So if you 
set id to 3, the first possible endpoint it returns is endpoint 4. No endpoint 
can have ID 0, so passing 0 gives you the first endpoint. If you pass NULL 
instead of an ID, NextEndpoint() always returns NULL. When the function 
returns, it sets id to the ID of the endpoint that was found. If no more 
endpoints exist, NextEndpoint() returns NULL and id is not changed. 
NextEndpoint() does <I>not</I> return locally created endpoints, even if they 
are Register()'ed.

Usage example:

\code
int32 id = 0;
BMidiEndpoint* endp;
while ((endp = BMidiRoster::NextEndpoint(&id)) != NULL) 
{
    ...do something with endpoint ...
    endp->Release();  // don't forget!
}
\endcode

Remember that NextEndpoint() bumps the endpoint's reference count, so you 
should always \link BMidiEndpoint::Release() Release() \endlink it when you are 
done.

*/

/*!
\fn BMidiProducer* BMidiRoster::NextProducer(int32* id)
\brief Returns the next producer from the roster

Like NextEndpoint(), but only returns producer endpoints.

\sa NextConsumer
\sa NextEndpoint
*/

/*!
\fn BMidiConsumer* BMidiRoster::NextConsumer(int32* id)
\brief Returns the next consumer from the roster

Like NextEndpoint(), but only returns consumer endpoints.

\sa NextProducer
\sa NextEndpoint
*/

/*!
\fn BMidiEndpoint* BMidiRoster::FindEndpoint(
        int32 id, bool localOnly = false)
\brief Returns the endpoint with the specified ID

FindEndpoint() will always find <I>any</I> local endpoints created by this 
application; they do not have to be published with Register() first. If 
localOnly is false, FindEndpoint() also looks at remote endpoints, otherwise 
only local endpoints will be resolved. Returns NULL if no such endpoint could 
be found.

You should use a dynamic_cast to convert the BMidiEndpoint into a producer or 
consumer:

\code
BMidiEndpoint* endp = ...;
BMidiProducer* prod = NULL;
BMidiConsumer* cons = NULL;

if (endp->IsProducer())
{
    prod = dynamic_cast<BMidiProducer*>(endp);
}
else if (endp->IsConsumer())
{
    cons = dynamic_cast<BMidiConsumer*>(endp);
}
\endcode

Remember that FindEndpoint() increments the endpoint's reference count, so you 
should always \link BMidiEndpoint::Release() Release() \endlink an endpoint 
when you are done with it:

\code
BMidiEndpoint* endp = BMidiRoster::FindEndpoint(someID);
if (endp != NULL) 
{
    ...do stuff with the endpoint...
    endp->Release();
}
\endcode

*/

/*!
\fn BMidiProducer* BMidiRoster::FindProducer(
        int32 id, bool localOnly = false)
\brief Finds the producer with the specified ID

Like FindEndpoint(), but only looks for producer endpoints. Returns NULL if no 
endpoint with that ID exists, or if that endpoint is not a producer.

\sa FindConsumer
\sa FindEndpoint
*/

/*!
\fn BMidiConsumer* BMidiRoster::FindConsumer(
        int32 id, bool localOnly = false)
\brief Finds the consumer with the specified ID

Like FindEndpoint(), but only looks for consumer endpoints. Returns NULL if no 
endpoint with that ID exists, or if that endpoint is not a consumer.

\sa FindProducer
\sa FindEndpoint
*/

/*!
\fn void BMidiRoster::StartWatching(const BMessenger* msngr)
\brief Start receiving notifications from the Midi Roster

When you start watching, BMidiRoster sends you notifications for all currently 
<I>published</I> <I>remote</I> endpoints, and all the current connections 
between them. (At this point, BMidiRoster does not let you know about 
connections between unpublished endpoints, nor does it tell you anything about 
your local endpoints, even though they may be published.)

Thereafter, you'll receive notifications any time something important happens 
to an object. The application that performs these operations is itself not 
notified. The assumption here is that you already know about these changes, 
because you are the one that is performing them.

The notifications are BMessages with code B_MIDI_EVENT. You specify the 
BMessenger that will be used to send these messages. Each message contains a 
field called be:op that describes the type of notification.

The "registered" and "unregistered" notifications are sent when a remote 
endpoint Register()'s or Unregister()'s, respectively. You don't receive these 
notifications when you register or unregister your local endpoints, but the 
other apps will.

<TABLE BORDER="1">
<TR><TD>be:op</TD><TD>int32</TD><TD>B_MIDI_REGISTERED</TD></TR>
<TR><TD>be:id</TD><TD>int32</TD><TD>ID of the endpoint</TD></TR>
<TR><TD>be:type</TD><TD>string</TD><TD>"producer" or "consumer"</TD></TR>
</TABLE>

<TABLE BORDER="1">
<TR><TD>be:op</TD><TD>int32</TD><TD>B_MIDI_UNREGISTERED</TD></TR>
<TR><TD>be:id</TD><TD>int32</TD><TD>ID of the endpoint</TD></TR>
<TR><TD>be:type</TD><TD>string</TD><TD>"producer" or "consumer"</TD></TR>
</TABLE>

The "connected" and "disconnected" notifications are sent when a consumer \link 
BMidiProducer::Connect() Connect()\endlink's to a producer, or when they \link 
BMidiProducer::Disconnect() Disconnect() \endlink. You will receive these 
notifications when <I>any</I> two endpoints connect or disconnect, even if they 
are not published. (The purpose of which is debatable.) You won't receive the 
notifications if you are the one making the connection, even if both endpoints 
are remote. You <I>will</I> be notified when another app connects one of your 
published endpoints.

<TABLE BORDER="1">
<TR><TD>be:op</TD><TD>int32</TD><TD>B_MIDI_CONNECTED</TD></TR>
<TR><TD>be:producer</TD><TD>int32</TD><TD>ID of the connector</TD></TR>
<TR><TD>be:consumer</TD><TD>int32</TD><TD>ID of the connectee</TD></TR>
</TABLE>

<TABLE BORDER="1">
<TR><TD>be:op</TD><TD>int32</TD><TD>B_MIDI_DISCONNECTED</TD></TR>
<TR><TD>be:producer</TD><TD>int32</TD><TD>ID of the connector</TD></TR>
<TR><TD>be:consumer</TD><TD>int32</TD><TD>ID of the connectee</TD></TR>
</TABLE>

The following notifications are sent when an endpoint's attributes are changed. 
You receive these notifications only if another application is changing one of 
its published endpoints.

<TABLE BORDER="1">
<TR><TD>be:op</TD><TD>int32</TD><TD>B_MIDI_CHANGED_NAME</TD></TR>
<TR><TD>be:id</TD><TD>int32</TD><TD>ID of the endpoint</TD></TR>
<TR><TD>be:type</TD><TD>string</TD><TD>"producer" or "consumer"</TD></TR>
<TR><TD>be:name</TD><TD>string</TD><TD>the endpoint's new name</TD></TR>
</TABLE>

<TABLE BORDER="1">
<TR><TD>be:op</TD><TD>int32</TD><TD>B_MIDI_CHANGED_LATENCY</TD></TR>
<TR><TD>be:id</TD><TD>int32</TD><TD>ID of the endpoint</TD></TR>
<TR><TD>be:type</TD><TD>string</TD><TD>"producer" or "consumer"</TD></TR>
<TR><TD>be:latency</TD><TD>int64</TD><TD>the new latency (microseconds)</TD></TR>
</TABLE>

<TABLE BORDER="1">
<TR><TD>be:op</TD><TD>int32</TD><TD>B_MIDI_CHANGED_PROPERTIES</TD></TR>
<TR><TD>be:id</TD><TD>int32</TD><TD>ID of the endpoint</TD></TR>
<TR><TD>be:type</TD><TD>string</TD><TD>"producer" or "consumer"</TD></TR>
<TR><TD>be:properties</TD><TD>BMessage</TD><TD>the new properties</TD></TR>
</TABLE>

Typical usage example:

\code
void MyView::AttachedToWindow()
{
    BMessenger msgr(this);
    BMidiRoster::StartWatching(&msgr);
}

void MyView::MessageReceived(BMessage* msg)
{
    switch (msg->what) 
    {
        case B_MIDI_EVENT:
            HandleMidiEvent(msg);
            break;
        default:
            super::MessageReceived(msg);
            break;
    }
}
\endcode

\sa \ref bmidiop "The possible be:op codes (BMidiOp)"
*/

/*!
\fn void BMidiRoster::StopWatching()
\brief Stop receiving notifications from the Midi Roster
\sa StartWatching()
*/

/*!
\fn status_t BMidiRoster::Register(BMidiEndpoint* object)
\brief Publishes an endpoint to other applications

Calls BMidiEndpoint's \link BMidiEndpoint::Register() Register() \endlink 
method to publish an endpoint, which makes it visible to other applications.

*/

/*!
\fn status_t BMidiRoster::Unregister(BMidiEndpoint* object)
\brief Hides an endpoint from other applications

Calls BMidiEndpoint's \link BMidiEndpoint::Unregister() Unregister() \endlink 
method to hide a previously published endpoint from other applications.

*/

/*!
\fn BMidiRoster* BMidiRoster::MidiRoster()
\brief Returns a pointer to the only instance of BMidiRoster

There is no real reason use this function, since all BMidiRoster's public 
function are static.

*/