Tt_address

Tt_address indicates which message attributes form the address to which the message will be delivered. Table 2-1 describes the possible values.

Table 2-1

Value	Description
TT_HANDLER	Addressed to a specific handler that can perform this operation with these arguments. Fill in handler, op, and arg attributes of the message or pattern.
TT_OBJECT	Addressed to a specific object that performs this operation with these arguments. Fill in object, op, and arg attributes of the message or pattern.
TT_OTYPE	Addressed to the type of object that can perform this operation with these arguments. Fill in otype, op, and arg attributes of the message or pattern.
TT_PROCEDURE	Addressed to any process that can perform this operation with these arguments. Fill in the op and arg attributes of the message or pattern.

Tt_callback

These values are used to specify the action taken by the callback attached to messages or patterns. If no callback returns TT_CALLBACK_PROCESSED, tt_message_receive() will return the message. Table 2-2 describes the possible values.

Table 2-2

Value	Description
TT_CALLBACK_CONTINUE	If the callback returns TT_CALLBACK_CONTINUE, other callbacks will be run.
TT_CALLBACK_PROCESSED	If the callback returns TT_CALLBACK_PROCESSED, no further callbacks will be invoked for this event, and the message will not be returned by tt_message_receive().

Tt_category

Tt_category values for the category attribute of a pattern indicate the receiver's intent. Table 2-3 describes the possible values.

Table 2-3

Value	Description
TT_OBSERVE	Just looking at the message. No feedback will be given to the sender.
TT_HANDLE	Will process the message, including filling in return values if any.

Tt_class

These values for the class attribute of a message or pattern indicate whether the sender wants an action to take place after the message has been received. Table 2-4 describes the possible values.

Table 2-4

Value	Description
TT_NOTICE	Notice of an event. Sender does not want feedback on this message.
TT_REQUEST	Request for some action to be taken. Sender must be notified of progress, success or failure, and must receive any return values.

Tt_disposition

Tt_disposition values indicate whether the receiving application should be started to receive the message or if the message should be queued until the receiving process is started at a later time. The message can also be discarded if the receiver is not started.

Note that Tt_disposition values can be added together, so that TT_QUEUE+TT_START means both to queue the message and to try to start a process. This can be useful if the start can fail (or be vetoed by the user), to ensure the message is processed as soon as an eligible process does start.

Table 2-5 describes the possible values.

Table 2-5

Value	Description
TT_DISCARD = 0	No receiver for this message. Message is returned to sender with the Tt_status field containing TT_FAILED.
TT_QUEUE = 1	Queue the message until a process of the proper ptype receives the message.
TT_START = 2	Attempt to start a process of the proper ptype if none is running.

Tt_filter

Tt_filter_action is the return value from a query callback filter procedure. Table 2-6 describes the possible values.

Table 2-6

Value	Description
TT_FILTER_CONTINUE	Continue the query, feed more values to the callback.
TT_FILTER_STOP	Stop the query, don't look for any more values.

Tt_mode

Tt_mode values specify whether the sender, handler, or observers writes a message argument. Table 2-7 describes the possible values.

Table 2-7

Value	Description
TT_IN	The argument is written by the sender and read by the handler and any observers.
TT_OUT	The argument is written by the handler and read by the sender and any reply observers.
TT_INOUT	The argument is written by the sender and the handler and read by all.

Tt_scope

Tt_scope values for the Scope attribute of a message or pattern indicate the set of processes eligible to receive the message. Table 2-8 describes the possible values.

Table 2-8

Value	Description
TT_SESSION	All processes joined to the indicated session are eligible.
TT_FILE	All processes joined to the indicated file are eligible.
TT_BOTH	All processes joined to either the indicated file or the indicated session are eligible.
TT_FILE_IN_SESSION	All processes joined to both the indicated session and the indicated file are eligible.

Tt_state

Tt_state values indicate a message's delivery status. Table 2-9 describes the possible values.

Table 2-9

Value	Description
TT_CREATED	Message has been created but not yet sent. (Only the sender of a message will see a message in this state.)
TT_SENT	Message has been sent but not yet handled.
TT_HANDLED	Message has been handled, return values are valid.
TT_FAILED	Message could not be delivered to a handler.
TT_QUEUED	Message has been queued for later delivery.
TT_STARTED	Attempting to start a process to handle the message.
TT_REJECTED	Message has been rejected by a possible handler. This state is seen only by the rejecting process. The ToolTalk service changes the state back to TT_SENT before delivering the message to another possible handler. If all possible handlers have rejected the message, the ToolTalk service changes the state to TT_FAILED before returning the message to the sender.

Tt_status

A Tt_status code is returned by all functions, sometimes directly and sometimes encoded in an error return value. See the ToolTalk User's Guide for instructions on to determine whether the Tt_status code is a warning or an error and for retrieving the error message string for a Tt_status code.

Chapter 7, "ToolTalk Error Messages," lists the Tt_status codes. The following information is provided for each status code:

• Message id
• Error message string
• Description
• Solution