haiku/docs/user/midi2/midiendpoint.dox

/*!
\class BMidiEndpoint
\ingroup midi2
\ingroup libmidi2
\brief Base class for all MIDI endpoints

BMidiEndpoint is the abstract base class that represents either a producer or 
consumer endpoint. It may be used to obtain the state, name, properties, or 
system-wide ID of the object. BMidiEndpoint also provides the ability to change 
the name and properties of endpoints that were created locally.

Remember, you cannot call the destructor of BMidiEndpoint and its subclasses 
directly. Endpoint objects are destructed automatically when their reference 
count drops to zero. If necessary, the destructor of a local endpoint first 
breaks off any connections and Unregister()'s the endpoint before it is 
deleted. However, for good style and bonus points you should really \link 
BMidiProducer::Disconnect() Disconnect() \endlink and Unregister() the object 
yourself and not rely on the destructor to do this.

*/

/*!
\fn const char* BMidiEndpoint::Name() const
\brief Returns the name of the endpoint

The function never returns NULL. If you created a local endpoint by passing a 
NULL name into its constructor (or passing no name, which is the same thing), 
then Name() will return an empty string, not NULL.

\sa SetName()

*/

/*!
\fn void BMidiEndpoint::SetName(const char* name)
\brief Changes the name of the endpoint.

Names don't have to be unique, but it is recommended that you give any 
endpoints you publish meaningful and unique names, so users can easily 
recognize what each endpoint does. There is no limit to the size of endpoint 
names.

Even though you can call this function on both remote and local objects, you 
are only allowed to change the names of local endpoints; SetName() calls on 
remote endpoints are ignored.

\param name The new name. If you pass NULL, the name simply won't be changed.

\sa Name()

*/

/*!
\fn int32 BMidiEndpoint::ID() const
\brief Returns the ID of the endpoint

An ID uniquely identifies an endpoint in the system. The ID is a signed 32-bit 
number that is assigned by the Midi Server when the endpoint is created. (So 
even if a local endpoint is not published, it still has a unique ID.) Valid IDs 
range from 1 to 0x7FFFFFFF, the largest value an int32 can have. 0 and negative 
values are <I>not</I> valid IDs.

*/

/*!
\fn bool BMidiEndpoint::IsProducer() const
\brief Determines whether this endpoint is a BMidiProducer

If it is, you can use a dynamic_cast to convert this object into a producer:

\code
if (endp->IsProducer())
{
    BMidiProducer* prod = dynamic_cast<BMidiProducer*>(endp);
    ....
}
\endcode
*/

/*!
\fn bool BMidiEndpoint::IsConsumer() const
\brief Determines whether this endpoint is a BMidiConsumer

If it is, you can use a dynamic_cast to convert this object into a consumer:

\code
if (endp->IsConsumer())
{
    BMidiConsumer* cons = dynamic_cast<BMidiConsumer*>(endp);
    ....
}
\endcode
*/

/*!
\fn bool BMidiEndpoint::IsRemote() const
\brief Determines whether this endpoint is a proxy for a remote object

An endpoint is "remote" when it is created by another application. Obviously, 
the remote object is Register()'ed as well, otherwise you would not be able to 
see it.

*/

/*!
\fn bool BMidiEndpoint::IsLocal() const
\brief Determines whether this endpoint represents a local object

An endpoint is "local" when it is created by this application; in other words, 
a BMidiLocalConsumer or BMidiLocalProducer.

*/

/*!
\fn bool BMidiEndpoint::IsPersistent() const
\brief Not used

The purpose of this function is unclear, and as a result it doesn't do anything
in the OpenBeOS implementation of the Midi Kit.

\return Always returns false.
*/

/*!
\fn bool BMidiEndpoint::IsValid() const
\brief Determines whether the endpoint still exists

Suppose you obtained a proxy object for a remote endpoint by querying the 
BMidiRoster. What if the application that published this endpoint quits, or 
less drastically, Unregister()'s that endpoint? Even though you still have a 
BMidiEndpoint proxy object, the real endpoint no longer exists. You can use 
IsValid() to check for this.

Don't worry, operations on invalid objects, such as GetProperties(), will 
return an error code (typically B_ERROR), but not cause a crash. Local objects 
are always are considered to be valid, even if you did not Register() them. 
(The only time a local endpoint is not valid is when there was a problem 
constructing it.)

If the application that created the remote endpoint crashes, then there is no 
guarantee that the Midi Server immediately recognizes this. In that case, 
IsValid() may still return true. Eventually, the stale endpoint will be removed 
from the roster, though. From then on, IsValid() correctly returns false.

*/

/*!
\fn status_t BMidiEndpoint::Acquire()
\brief Increments the endpoint's reference count

Each BMidiEndpoint has a reference count associated with it, so that 
BMidiRoster can do proper bookkeeping. Acquire() increments this reference 
count, and Release() decrements it. Once the count reaches zero, the endpoint 
is deleted.

When you are done with the endpoint, whether local or remote, you should 
<I>always</I> Release() it!

Upon construction, local endpoints start with a reference count of 1. Any 
objects you obtain from BMidiRoster using the NextXXX() or FindXXX() functions 
have their reference counts incremented in the process. If you forget to call 
Release(), the objects won't be properly cleaned up and you'll make a fool out 
of yourself.

After you Release() an object, you are advised not to use it any further. If 
you do, your app will probably crash. That also happens if you Release() an 
object too many times.

Typically, you don't need to call Acquire(), unless you have two disparate 
parts of your application working with the same endpoint, and you don't want to 
have to keep track of who needs to Release() the endpoint. Now you simply have 
both of them release it.

\return Always returns B_OK
\sa Release()
*/

/*!
\fn status_t BMidiEndpoint::Release()
\brief Decrements the endpoint's reference count
\return Always returns B_OK
\sa Acquire()
*/

/*!
\fn status_t BMidiEndpoint::Register()
\brief Publishes the endpoint on the roster

MIDI objects created by an application are invisible to other applications 
until they are published. To publish an object use the Register() method. The 
corresponding Unregister() method will cause an object to once again become 
invisible to remote applications.

BMidiRoster also has Register() and Unregister() methods. You may also use 
those methods  to publish or hide your endpoints; both do the same thing.

Although it is considered bad style, calling Register() on local endpoints that 
are already registered won't mess things up. The Midi Server will simply ignore 
your request. Likewise for Unregister()'ing more than once. Attempts to 
Register() or Unregister() remote endpoints will fail, of course.

If you are \link BMidiRoster::StartWatching() watching \endlink, you will 
<I>not</I> receive notifications for any local endpoints you register or 
unregister. Of course, other applications <I>will</I> be notified about your 
endpoints.

Existing connections will not be broken when an object is unregistered, but 
future remote connections will be denied. When objects are destroyed, they 
automatically become unregistered.

\return B_OK on success, or a negative error code (typically B_ERROR) if 
something went wrong.

\sa Unregister()
*/

/*!
\fn status_t BMidiEndpoint::Unregister()
\brief Hides the endpoint from the roster
\sa Register()
*/

/*!
\fn status_t BMidiEndpoint::SetProperties(const BMessage* props)
\brief Changes the properties of the endpoint

Endpoints can have properties, which is any kind of information that might be 
useful to associate with a MIDI object. The properties are stored in a 
BMessage.

Usage example:

\code
BMessage props;
if (endpoint->GetProperties(&props) == B_OK)
{
    ...add data to the message...
    endpoint->SetProperties(&props);
} 
\endcode

You are only allowed to call SetProperties() on a local object.

Properties should follow a protocol, so different applications will know how to 
read each other's properties. The current protocol is very limited -- it only 
allows you to associate icons with your endpoints. Be planned to publish a more 
complete protocol that included additional information, such as vendor/model 
names, copyright/version info, category, etc., but they never got around to it.

<TABLE BORDER="1">
<TR><TD>property</TD><TD>Vector icon (raw data)</TD></TR>
<TR><TD>field name</TD><TD>"icon"</TD></TR>
<TR><TD>field type</TD><TD>'VICN'</TD></TR>
</TABLE>

This vector icon is available under Haiku only, and comes as raw data, not a BBitmap. 
Before being able to display it, you first must render the vector icon in the size of 
your choice.

<TABLE BORDER="1">
<TR><TD>property</TD><TD>Large (32x32) icon</TD></TR>
<TR><TD>field name</TD><TD>"be:large_icon"</TD></TR>
<TR><TD>field type</TD><TD>'ICON'</TD></TR>
</TABLE>

<TABLE BORDER="1">
<TR><TD>property</TD><TD>Small (16x16) icon</TD></TR>
<TR><TD>field name</TD><TD>"be:mini_icon"</TD></TR>
<TR><TD>field type</TD><TD>'MICN'</TD></TR>
</TABLE>

The MidiUtil package (downloadable from the OpenBeOS website) contains a number 
of convenient functions to associate icons with endpoints, so you don't have to 
write that code all over again.

\sa GetProperties()
*/

/*!
\fn status_t BMidiEndpoint::GetProperties(BMessage* props) const
\brief Reads the properties of the endpoint

Usage example:

\code
BMessage props;
if (endpoint->GetProperties(&props) == B_OK) 
{
    ...examine the contents of the message...
}
\endcode

Note that GetProperties() overwrites the contents of your BMessage.

\sa SetProperties()
*/