Update BInvoker docs to clarify them

...with notes from PulkoMandy and Axel. Also added author credits.

Class documentation is moved to the appropriate method and then \sa
is used to point to the documentation so it is only documented in
one location.

Added some text about how the interaction between BInvoker and
BHandler and/or BLooper works.

BMessenger needs to be documented to understand how SetTimeout() is
suppose to work, refer to BeBook for now.

docs/user/app/Invoker.dox

@@ -3,6 +3,8 @@
  * Distributed under the terms of the MIT License.
  *
  * Authors:
+ *		Adrien Destugues, [email protected]
+ *		Axel Dörfler, [email protected]
  *		John Scipione, [email protected]
  *
  * Corresponds to:
@@ -25,14 +27,14 @@
 	\ingroup libbe
 	\brief An object that can be "invoked" to send a message to a BHandler.
 
-	When Invoke() is called, the message is sent to the designated BHandler
-	known as the "target". The message is sent as a BMessage. The message is
-	not copied, rather ownership of the BMessage object is transferred to
-	the invoker.
+	The designated BHandler of a BInvoker is known as its "target".
 
 	BInvoker is most often used as a mix-in class, for example, BControl
 	derives from BInvoker as well as from BView.
 
+	\sa Invoke()
+	\sa SetTarget(const BHandler*, const BLooper*) for details.
+
 	\since BeOS R3
 */
 
@@ -44,7 +46,7 @@
 
 	A BMessenger can target either local or remote objects.
 
-	\sa Invoke()
+	\sa SetMessage() for details.
 
 	\since BeOS R3
 */
@@ -61,6 +63,7 @@
 	      \a looper, the unused parameter should be passed in as \c NULL.
 
 	\sa Invoke()
+	\sa SetTarget(const BHandler*, const BLooper*) for details.
 
 	\since BeOS R3
 */
@@ -100,6 +103,11 @@
 	You may pass \c NULL into \a message to delete the current message
 	without replacing it.
 
+	When Invoke() is called, the message is sent to the designated BHandler
+	known as the "target". The message is sent as a BMessage. The message is
+	not copied, rather ownership of the BMessage object is transferred to
+	the invoker.
+
 	\since BeOS R3
 */
 
@@ -117,7 +125,7 @@
 
 /*!
 	\fn uint32 BInvoker::Command() const
-	\brief Returns the messages \c what data member.
+	\brief Returns the message's \c what data member.
 
 	\note If a message has not been assigned to the invoker this method
 	      returns \c NULL instead.
@@ -143,6 +151,13 @@
 	\note It is not necessary to specify both the \a handler and the
 	      \a looper, the unused parameter should be passed in as \c NULL.
 
+	If given a \a handler, it must be attached to a BLooper. The message
+	is always sent to a BLooper which distributes the message to the
+	correct handler (which might be the \a looper itself).
+
+	The preferred handler, i.e. for a window, is the view that currently
+	has focus.
+
 	\since BeOS R3
 */
 
@@ -221,6 +236,9 @@
 	of the invoker's handler will receive their expected notifications.
 	By default, \a kind is \c B_CONTROL_INVOKED, the same as sent by Invoke().
 
+	\sa BLooper::StartWatching()
+	\sa BHandler::NoticeChange()
+
 	\since BeOS R5
 */
 
@@ -229,7 +247,10 @@
 	\fn status_t BInvoker::SetTimeout(bigtime_t timeout)
 	\brief Sets the timeout to use when sending the message to the target.
 
-	By default the timeout is set to \c B_INFINITE_TIMEOUT.
+	By default the timeout is set to \c B_INFINITE_TIMEOUT. The \a timeout
+	value is passed into the timeout parameter of BMessenger::SendMessage().
+
+	\sa BMessenger::SendMessage(BMessage*, BHandler*, bigtime_t) for details.
 
 	\since BeOS R5
 */