Copyright ã1995 by NeXT Computer, Inc.  All Rights Reserved.

DPSAddFD(), DPSRemoveFD()

	SUMMARY	Monitor a file descriptor

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	void DPSAddFD(int fd, DPSFDProc handler, void *userData, int priority) 
void DPSRemoveFD(int fd)

	DESCRIPTION	DPSAddFD() registers the function handler to be called each time there is activity with the file specified by file descriptor fd.  The function is called provided the following are true:

·	The file descriptor fd must be valid and open; typically fd is generated through a call to open().  There needn't be any data waiting to be read on fd.

·	priority, an integer from 0 to 30, must be equal to or greater than the application's current priority threshold.  See DPSAddTimedEntry() for a further explanation.

DPSFDProc, handler's defined type, takes the form

void *handler(int fd, void *userData)

where fd is the file descriptor that prompted the function call and userData is the same pointer that was passed as the third argument to DPSAddFD().  The userData pointer is provided as a convenience, allowing you to pass arbitrary data to handler. 

DPSRemoveFD() removes the specified file descriptor from the list of those that the application will check.  

Typically, DPSAddFD() is used to listen to a socket or pipe; it's rarely used to monitor a common file.

	SEE ALSO	DPSAddPort(), DPSAddTimedEntry()

DPSAddNotifyPortProc(), DPSRemoveNotifyPortProc()

	SUMMARY	Set the handler function for the notify port

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	void DPSAddNotifyPortProc(DPSPortProc handler, void *userData) 
void DPSRemoveNotifyPortProc(DPSPortProc handler)

	DESCRIPTION	DPSAddNotifyPortProc() registers handler as the function that's called when a message arrives on the notify port, the unique port, created through the task_notify() Mach function, on which notifications (such as port death) are sent.  You don't need to create the notify port yourself; DPSAddNotifyPortProc() creates it for you if it doesn't already exist.  

DPSPortProc, handler's defined type, takes the form

void *handler(msg_header_t *msg, void *userData)

where msg is a pointer to the message that was received at the port and userData is the same pointer that was passed as the second argument to DPSAddNotifyPortProc().  The userData pointer is provided as a convenience, allowing you to pass arbitrary data to handler.

The notify port can have only one handler at a time; adding a handler removes the current one.  You can remove the port's handler without specifying a new one with the DPSRemoveNotifyPortProc() function.  The function's argument must match the notify port's current handler. 

	SEE ALSO	DPSAddPort(), DPSAddTimedEntry()

DPSAddPort(), DPSRemovePort()

	SUMMARY	Monitor a Mach port

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	void DPSAddPort(port_t port, DPSPortProc handler, int maxMsgSize, void *userData, int priority) 
void DPSRemovePort(port_t port)

	DESCRIPTION	DPSAddPort() registers the function handler to be called each time your application asks for an event or peeks at the event queue.  The function is called provided the following are true:

·	The Mach port port  must be valid and it must hold a message waiting to be read. 

·	priority, an integer from 0 to 30, must be equal to or greater than the application's current priority threshold.  See DPSAddTimedEntry() for a further explanation.

DPSPortProc, handler's defined type, takes the form

void *handler(msg_header_t *msg, void *userData)

where msg is a pointer to the message that was received at the port and userData is the same pointer that was passed as the fourth argument to DPSAddPort().  The userData pointer is provided as a convenience, allowing you to pass arbitrary data to handler.

If, within handler, you want to call msg_receive() to receive further messages at the port, you must first call DPSRemovePort() to remove the port from the system's port set.  (This is because your application can't receive messages from a port that's in a port set.)  After your application is finished receiving messages directly from the port, it can call DPSAddPort() to have the system continue to monitor the port.

The contents of the message buffer msg, as received by handler, are invalid after the function returns.  If you need to save any of the information that you find.

The maxMsgSize argument is an integer that gives the size, in bytes, of the largest message you expect to receive. 

DPSRemovePort() removes the specified Mach port from the list of those that the application will check.  

	SEE ALSO	DPSAddFD(), DPSAddTimedEntry()

DPSAddTimedEntry(), DPSRemoveTimedEntry()

	SUMMARY	Create a timed entry

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	DPSTimedEntry DPSAddTimedEntry(double  period, DPSTimedEntryProc handler, void *userData, int priority) 
void DPSRemoveTimedEntry(DPSTimedEntry tag)

	DESCRIPTION	DPSAddTimedEntry() registers handler as a ªtimed entry,º a function that's called repeatedly at a given time interval.  period determines the number of seconds between calls to the timed entry.  Whenever an application based on the Application Kit attempts to retrieve events from the event queue, it also checks (depending on priority) to determine whether any timed entries are due to be called.  userData is a pointer that you can use to pass some data to the timed entry.

The function registered as handler has the form:

void *handler(DPSTimedEntry tag, double now, void *userData)

where tag is the timed entry identifier returned by DPSAddTimedEntry(), now is the number of seconds since some arbitrary point in the past, and userData is the pointer DPSAddTimedEntry() received when this timed entry was installed.

An application's priority threshold can be set explicitly as an integer from 0 to 31 through a call to DPSGetEvent() or DPSPeekEvent().  It's against this threshold that priority is measured (note that priority can be no greater than 30Ðthe additional threshold level, 31, is provided to disallow all inter-event function calls).  However, if you're using the Application Kit, you should access the event queue through Application class methods such as getNextEvent:.  Although some of these methods let you set the priority threshold explicity, you typically invoke the methods that set it automatically.  Such methods use only three priority levels:

Constant	Meaning

NX_BASETHRESHOLD	Normal execution
NX_RUNMODALTHRESHOLD	An attention panel is being run
NX_MODALRESPTHRESHOLD	A modal event loop is being run

When applicable, you should use these constants as the value for priority.  For example, if you want handler to be called during normal execution, but not if an attention panel or a modal loop is running, then you would set priority to NX_BASETHRESHOLD.  

DPSRemoveTimedEntry() removes a previously registered timed entry.

	RETURN	DPSAddTimedEntry() returns a number identifying the timed entry or -1 to indicate an error.

DPSAsynchronousWaitContext()

	SUMMARY	Procede asynchronously while PostScript code is executed

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	void DPSAsynchronousWaitContext(DPSContext context, DPSPingProc handler,
void *userData)

	DESCRIPTION	This function is similar to the more familiar DPSWaitContext() functions, except that rather than wait for all PostScript code to execute, it returns immediately, allowing your application to procede while the PostScript code is executed in the background.  The DPSPingProc function handler is called (with context and userData as its two arguments) when all the PostScript code has been executed.  The DPSPingProc function takes the form

void *handler(DPSContext context, void *userData);

Warning:  Be careful when you use this function; you mustn't send more PostScript code while waiting for the handler to be called.  In general, it's best to not make any demands on the Application Kit or the Client Library if you're waiting for an asynchronous handler to return.

DPSCreateContext(), DPSCreateContextWithTimeoutFromZone(), DPSCreateNonsecureContext(), DPSCreateStreamContext()

	SUMMARY	Create a PostScript execution context

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	DPSContext DPSCreateContext(const char *hostName, const char *serverName, DPSTextProc textProc, DPSErrorProc errorProc)
DPSContext DPSCreateContextWithTimeoutFromZone(const char *hostName, const char *serverName, DPSTextProc textProc, DPSErrorProc errorProc, int timeout, NXZone *zone) 
DPSContext DPSCreateNonsecureContext(const char *hostName, const char *serverName, DPSTextProc textProc, DPSErrorProc errorProc, int timeout, NXZone *zone) 
DPSContext DPSCreateStreamContext(NXStream *stream, int debugging, DPSProgramEncoding progEnc, DPSNameEncoding nameEnc, DPSErrorProc errorProc)

	DESCRIPTION	DPSCreateContext() establishes a connection with the Window Server and creates a PostScript execution context in it.  The new context becomes the current context.  The first argument, hostName, identifies the machine that's running the Window Server; the second argument, serverName, identifies the Window Server that's running on that machine.  With these two arguments and the help of the Mach network server nmserver, the Mach port for the Window Server can be identified.  If hostName is NULL, the network server on the local machine is queried for the Window Server's port.  If serverName is NULL, a default name for the Window Server is used.  

The last two arguments, textProc and errorProc, refer to call-back functions (defined in the Client Library specification) that handle text returned from the Window Server and errors generated on either side of the connection. 

For an application that's based on the Application Kit, you could create an additional context by making this call:

DPSContext  c;

c = DPSCreateContext(NXGetDefaultValue([NXApp appName], "NXHost"),
                   NXGetDefaultValue([NXApp appName], "NXPSName"),
                   NULL,
                   NULL);

This example queries the application's default values for the indentity of the host machine and the Window Server.  By doing this, the new context is created in the correct Window Server even if that Server is not on the same machine as the application process.  

The context that DPSCreateContext() creates allocates memory from the default allocation zone.  Also, when there's difficulty creating the context, DPSCreateContext() waits up to 60 seconds before raising an exception.  If you want to change either of these parameters, use DPSCreateContextWithTimeoutFromZone().  Its two additional arguments let you specify the zone for the context to use when allocating context-specific data and a timeout value in milliseconds.

DPSCreateNonsecureContext() creates a ªnonsecureº context in which you can use PostScript operators that are normally disallowed.  The most significant of these are operators that let you write files.

DPSCreateStreamContext() is similar to DPSCreateContext(), except that the new context is actually a connection from the client application to a stream.  This connection becomes the current context.  PostScript code that the application generates is sent to the stream rather than to the Window Server.  The first argument, stream, is a pointer to an NXStream structure, as created by NXOpenFile() or NXMapFile().  The debugging argument is intended for debugging purposes but is not currently implemented.  progEnc and nameEnc specify the type of program and user-name encodings to be used for output to the stream.  The last argument, errorProc, identifies the procedure that's called when errors are generated.

Few programmers will need to call either of these functions directly:  The Application Kit manages contexts for programs based on the Kit.  For example, when an application is launched, its Application object calls DPSCreateContext() to create a context in the Window Server.  Similarly, to print a View the Kit calls DPSCreateStreamContext() to temporarily redirect PostScript code from the View to a stream.

	RETURN	Each of these functions returns the newly created DPSContext structure.

	EXCEPTIONS	DPSCreateContext() and DPSCreateContextWithTimeoutFromZone() raise a dps_err_outOfMemory exception if they encounter difficulty allocating ports or other resources for the new context.  They raise a dps_err_cantConnect exception if they can't return a context within the timeout period.

DPSCreateContextWithTimeoutFromZone() ® See DPSCreateContext()

DPSCreateNonsecureContext() ® See DPSCreateContext()

DPSCreateStreamContext() ® See DPSCreateContext()

DPSDefineUserObject(), DPSUndefineUserObject()

	SUMMARY	Create a user object

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	int DPSDefineUserObject(int index)
void DPSUndefineUserObject(int index)

	DESCRIPTION	DPSDefineUserObject() associates index with the PostScript object that's on the top of the operand stack, thereby creating a user object (as defined by the PostScript language).  If index is 0, the object is assigned the next available index number.  The function returns the new index, which can then be passed to a pswrap-generated function that takes a user object.

Warning:  To avoid coming into conflict with user objects defined by the Client Library or Application Kit, use DPSDefineUserObject() rather than the PostScript operator defineuserobject or the single-operator functions DPSdefineuserobject() and PSdefineuserobject().

DPSUndefineUserObject() removes the association between index and the PostScript object it refers to, thus destroying the user object.  By destroying a user object that's no longer needed, you can let the garbage collector reclaim the previously associated PostScript object.

	RETURN	DPSDefineUserObject(), if successful in assigning an index, returns the index that the object was assigned.  If unsuccessful, it returns 0.

DPSDiscardEvents() ® See DPSGetEvent()

DPSDoUserPath(), DPSDoUserPathWithMatrix()

	SUMMARY	Send an encoded PostScript path to the Window Server

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	void DPSDoUserPath(void *coords, int numCoords, DPSNumberFormat numType, unsigned char *ops, int numOps, void *bbox, int action)
void DPSDoUserPathWithMatrix(void *coords, int numCoords, DPSNumberFormat numType, unsigned char *ops, int numOps, void *bbox, int action, float matrix[6])

	DESCRIPTION	DPSDoUserPath() and DPSDoUserPathWithMatrix() send an encoded user path to the Window Server and then execute, upon that path, the operator specified by action.  The use of these functions, rather than the analogous step-by-step path construction, is encouraged; rendering an encoded path is much more efficient than executing the individual PostScript operators that would otherwise be needed.

An encoded user path consists of an array of coordinate values, a sequence of PostScript operators, and a bounding box specification.  The values in the coordinate array are used as operands to the operators; the operands are distributed to the operators in the order that they're given.  The resulting path must fit within the bounding box.  

The coordinates, operators, and bounding box are given by the functions' first five arguments:

·	The array of coordinate values is given by coords. 

·	numCoords is the number of elements in coords.

·	 numType specifies the data type of the coordinates, as described below.  All the values in coords must be of the same type.

·	ops is the sequence of PostScript operators, represented by constants as listed below. 

·	The  bounding box is defined by the four coordinate values that you pass as an array in the bbox argument.  These are passed as operands to the setbbox operator.  (If you don't supply a setbbox as part of the ops sequence, one is inserted for you.) 

The following integer constants represent the data types that you can pass as the numType argument:

Constant	Meaning

dps_float	single-precision floating-point number
dps_long	32-bit integer
dps_short	8-bit integer

You can also specify 16- and 32-bit fixed-point real numbers.  For 16-bit fixed-point numbers, use dps_short plus the number of bits in the fractional portion.  For 32-bit fixed-point numbers, use dps_long plus the number of bits in the fractional portion. 

These constants are provided for ops:

dps_setbbox
dps_moveto
dps_rmoveto
dps_lineto
dps_rlineto
dps_curveto
dps_rcurveto
dps_arc
dps_arcn
dps_arct
dps_closepath
dps_ucache

Once the user path has been constructed, the operator specified by action is executed.  The value of action is an index into Display PostScript's encoded system names; the following constants, provided as a convenience, represent the most commonly used actions:

dps_uappend
dps_ufill
dps_ueofill
dps_ustroke
dps_ustrokepath
dps_inufill
dps_inueofill
dps_inustroke
dps_def
dps_put

DPSDoUserPathWithMatrix()'s matrix argument represents the transformation matrix operand used by the ustroke, inustroke, and ustrokepath operators.  If matrix is NULL, the argument is ignored.

The following program fragment demonstrates the use of DPSDoUserPath() as it creates and strokes a user path (an isosceles triangle) within a bounding rectangle whose lower left corner is located at (0, 0) and whose width and height are 200.

short   coords[6] = {0, 0, 200, 0, 100, 200};
char    ops[4] = {dps_moveto, dps_lineto,dps_lineto, 
                    dps_closepath};
short   bbox[4] = {0, 0, 200, 200};

DPSDoUserPath(coords, 6, dps_short, ops, 4, bbox, dps_ustroke);

Note:  If an application calls DPSDoUserPath() with large values (~10,000-20,000) of numCoords and/or numOps, it may generate a Display PostScript error.

DPSDoUserPathWithMatrix() ® See DPSDoUserPath()

DPSFlush(), DPSSendEOF() 

	SUMMARY	Send PostScript data to the Window Server

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	void DPSFlush()
void DPSSendEOF(DPSContext context)

	DESCRIPTION	DPSFlush() flushes the application's output buffer, forcing any buffered PostScript code or data to the Window Server.  

DPSSendEOF() sends a PostScript end-of-file marker to the given context.  The connection to the context isn't closed or disturbed in any way by this function.

DPSGetEvent(), DPSPeekEvent(), DPSDiscardEvents() 

	SUMMARY	Access events from the Window Server

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	int DPSGetEvent(DPSContext context, NXEvent *anEvent, int mask, double timeout, int threshold) 
int DPSPeekEvent(DPSContext context, NXEvent *anEvent, int mask, double timeout, int threshold) 
void DPSDiscardEvents(DPSContext context, int mask)

	DESCRIPTION	DPSGetEvent() and DPSPeekEvent() are macros that access event records in an application's event queue.  These routines are provided primarily for programs that don't use the Application Kit.  An application based on the Kit should use the corresponding Application class methods (such as getNextEvent: and peekNextEvent:into:) or the function NXGetOrPeekEvent() so that it can be journaled.  DPSDiscardEvents() removes all event records of a specified type from the queue.

DPSGetEvent() and DPSPeekEvent() differ only in how they treat the accessed event record.  DPSGetEvent() removes the record from the queue after making its data available to the application; DPSPeekEvent() leaves the record in the queue.  

DPSGetEvent() and DPSPeekEvent() take the same parameters.  The first, context, represents a PostScript execution context within the Window Server.  Virtually all applications have only one execution context, which can be returned using DPSGetCurrentContext().  Applications having more than one execution context can use the constant DPS_ALLCONTEXTS to access events from all contexts belonging to them.

The second argument, anEvent, is a pointer to an event record.  If DPSGetEvent() or DPSPeekEvent() is successful in accessing an event record, the record's data is copied into the storage referred to by anEvent.  

mask determines the types of events sought.  See the section ªTypes and Constantsº for a list of the constants that represent the event type masks.  To check for more than one type of event, you combine individual constants using the bitwise OR operator.

If an event matching the event mask isn't available in the queue, DPSGetEvent() or DPSPeekEvent() waits until one arrives or until timeout seconds have elapsed, whichever occurs first.  The value of timeout can be in the range of 0.0 to NX_FOREVER.  If timeout is 0.0, the routine returns an event only if one is waiting in the queue when the routine asks for it.  If timeout is NX_ FOREVER, the routine waits until an appropriate event arrives before returning.  

The last argument, threshold, is an integer in the range 0 through 31 that determines which other services may be provided during a call to DPSGetEvent() or DPSPeekEvent().  

Requests for services are registered by the functions DPSAddTimedEntry(), DPSAddPort(), and DPSAddFD().  Each of these functions takes an argument specifying a priority level.  If this level is equal to or greater than threshold, the service is provided before DPSGetEvent() or DPSPeekEvent() returns.  

DPSDiscardEvents()'s two parameters, context and mask, are the same as those for DPSGetEvent() and DPSPeekEvent().  DPSDiscardEvents() removes from the application's event queue those records whose event types match mask and whose context matches context.  

	RETURN	DPSGetEvent() and DPSPeekEvent() return 1 if they are successful in accessing an event record and 0 if they aren't.

	SEE ALSO	DPSAddFD(), DPSAddPort(), DPSAddTimedEntry(), DPSPostEvent(), NXGetOrPeekEvent()

DPSInterruptContext() 

Warning:  This function is unimplemented in the NEXTSTEP version of the Client Library.

DPSNameFromTypeAndIndex() 

	SUMMARY	Access the system and user name tables

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	const char *DPSNameFromTypeAndIndex(short type, int index)

	DESCRIPTION	DPSNameFromTypeAndIndex() returns the text associated with index from the system or user name table.  If type is -1, the text is returned from the system name table; if type is 0, it's returned from the user name table.  

The name tables are used primarily by the Client Library and pswrap; few programmers will access them directly.  

	RETURN	This function returns a read-only character string.

DPSPeekEvent() ® See DPSGetEvent()

DPSPostEvent() 

	SUMMARY	Create an event

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	int DPSPostEvent(NXEvent *anEvent, int atStart)

	DESCRIPTION	DPSPostEvent() lets you add an event record to your application's event queue without involving the Window Server.  anEvent is a pointer to the event record to be added.  atStart specifies where the new record will be placed in relation to any other records in the queue.  If atStart is TRUE, the event is posted in front of all others and so will be the next one your application receives.  If atStart is FALSE, the event is posted behind all others and so won't be returned until events that precede it are processed.

You can free, reuse, or otherwise mangle anEvent after you've posted it without fear of corrupting the posted record.  DPSEvent() copies the record it receives and posts the copy.  

Note that event records you post using DPSPostEvent() aren't filtered by an event filter function set with DPSSetEventFunc().

	RETURN	DPSPostEvent() returns 0 if successful in posting the event record; it returns -1 if unsuccessful in posting the record because the event queue is full.

	SEE ALSO	DPSSetEventFunc()

DPSPrintError(), DPSPrintErrorToStream() 

	SUMMARY	Print error messages

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	void DPSPrintError(FILE *fp, const DPSBinObjSeq error)
void DPSPrintErrorToStream(NXStream *stream, const DPSBinObjSeq error)

	DESCRIPTION	DPSPrintError() and DPSPrintErrorToStream() format and print error messages received from a PostScript execution context in the Window Server.  The error message is extracted from the binary object sequence error.  DPSPrintError() prints the error message to the file identified by fp; DPSPrintErrorToStream() prints the error message to stream.  

You rarely need to call these functions directly.  However, if you reset the error handler for a PostScript execution context, the new handler you install could use one of these functions to process errors that it receives.    

DPSPrintErrorToStream() ® See DPSPrintError()

DPSRemoveFD() ® See DPSAddFD()

DPSRemovePort() ® See DPSAddPort()

DPSRemoveTimedEntry() ® See DPSAddTimedEntry() 

DPSResetContext() 

Warning:  This function is unimplemented in the NEXTSTEP version of the Client Library.

DPSSetDeadKeysEnabled() 

	SUMMARY	Allow dead key processing for a context's events

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	void DPSSetDeadKeysEnabled(DPSContext context, int flag)

	DESCRIPTION	DPSSetDeadKeysEnabled() turns dead key processing on or off for context.  If flag is 0, dead key processing is turned off; otherwise, it's turned on (the default).

Dead key processing is a technique for extending the range of characters that can be entered from the keyboard.  In NEXTSTEP, it provides one way for users to enter accented characters.  For example, a user can type Alternate-e followed by the letter ªeºº to produce the letter ªÝºº.  The first keyboard input, Alternate-e, seems to have no effectÐit's the ªdead keyºº.  However, it signals Client Library routines that it and the following character should be analyzed as a pair.  If, within NEXTSTEP, the pair of characters has been associated with a third character, a keyboard event record representing the third character is placed in the application's event queue, and the first two event records are discarded.  If there is no such association between the two characters, the two event records are added to the event queue.  

See the NeXT User's Reference manual for a listing of the keys that produce accent characters.

DPSSetEventFunc() 

	SUMMARY	Set the function that filters events

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	DPSEventFilterFunc DPSSetEventFunc(DPSContext context, DPSEventFilterFunc func)

	DESCRIPTION	DPSSetEventFunc() establishes the function func as the function to be called when an event record is returned from the PostScript context context in the Window Server.  The registered function is called before the event record is put in the event queue.  If the registered function returns 0, the record is discarded.  If the registered function returns 1, the record is passed on for further processing.

Only event records coming from the Window Server are filtered by the registered function.  Records that you post to the event queue using DPSPostEvent() aren't affected.

A DPSEventFilterFunc function takes the following form:

int *func(NXEvent *anEvent)

	RETURN	DPSSetEventFunc() returns a pointer to the previously registered event function.  This lets you chain together the current and previous event functions.

	SEE ALSO	DPSPostEvent()

DPSSetTracking() 

	SUMMARY	Coalesce mouse events

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	int DPSSetTracking(int flag)

	DESCRIPTION	DPSSetTracking() turns mouse event-coalescing on or off for the current context.  If flag is 0, coalescing is turned off; otherwise, it's turned on (the default).

Event coalescing is an optimization that's useful when tracking the mouse.  When the mouse is moved, numerous events flow into the event queue.  To reduce the number of events awaiting removal by the application, adjacent mouse-moved events are replaced by the most recent event of the contiguous group.  The same is done for left and right mouse-dragged events, with the addition that a mouse-up event replaces mouse-dragged events that come before it in the queue.

	RETURN	DPSSetTracking() returns the previous state of the event-coalescing switch.

DPSStartWaitCursorTimer() 

	SUMMARY	Initiate a count down for the wait cursor 

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	void DPSStartWaitCursorTimer()

	DESCRIPTION	DPSStartWaitCursorTimer() triggers the mechanism that displays a wait cursor when an application is busy and can't respond to user input.  In most cases, wait cursor support is automatic:  You'll only need to call this function if your application starts a time-consuming operation that's not initiated by a user-generated event.

Client Library routines and the Window Server cooperate to display the wait cursor whenever more than a preset amount of time elapses between the time an application takes an event record from the event queue and the time the application is again ready to consume events.  However, when an application starts an operation that isn't initiated by an eventÐsuch as one caused by receiving a Mach message or by processing data from a file (see DPSAddPort() and DPSAddFD())Ðthe wait cursor mechanism is bypassed.  To ensure proper wait cursor behavior in these cases, call DPSStartWaitCursorTimer() before beginning the time-consuming operation.

	SEE ALSO	DPSAddFD(), DPSAddPort(), setwaitcursorenabled

DPSSynchronizeContext()

	SUMMARY	Synchronize a context with your application

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	int DPSSynchronizeContext(DPSContext context, int flag)

	DESCRIPTION	DPSSynchronizeContext() causes DPSWaitContext() to be called after each pswrap function is called, thus synchronizing the PostScript context with your application.

DPSTraceContext(), DPSTraceEvents()

	SUMMARY	Trace data and events

	DECLARED IN	dpsclient/dpsNeXT.h

	SYNOPSIS	int DPSTraceContext(DPSContext context, int flag)
void DPSTraceEvents(DPSContext context, int flag)

	DESCRIPTION	DPSTraceContext() and DPSTraceEvents() control the tracing of data and events between a PostScript execution context (or contexts) in the Window Server and an application process.  

The first argument for both functions, context, specifies the context to be traced.  An application's single context can be returned with DPSGetCurrentContext().  Applications having more than one execution context can use the constant DPS_ALLCONTEXTS to trace all contexts belonging to them.

The second argument, flag, determines whether tracing is enabled.  

When data tracing is enabled (DPSTraceContext()), a copy of the PostScript code generated by an application and the values returned to it by the Window Server is sent to UNIX standard error.  Values returned to the application are marked by the prepended string:

% value returned ==>

When event tracing is enabled (DPSTraceEvents()), information about each event that the application receives is sent to UNIX standard error.  For example, for a left mouse-down event the listing might look like this:

Receiving: LMouseDown at: 343.0,69.0 time: 1271899 
            flags: 0x0 win: 6 ctxt: 76128 data: 1111,1

The listing displays the fields of the event record:  type, location, time, flags, local window number, PostScript execution context, and data.  The contents of the data field listing depends on the event type; for instance, in the preceding example the event number and the click count were displayed. 

For applications based on the Application Kit, there are two preferable methods for turning on data tracing:  You can use the NXShowPS command-line switch when you launch an application from Terminal.  Alternatively, when you run the application under GDB, you can use the showps and shownops commands to control tracing output.  Similarly, there are more convenient ways to turn on event tracing:  You can use the NXTraceEvents command-line switch when you launch an application from Terminal.  Alternatively, when you run the application under GDB, you can use the traceevents and tracenoevents commands to control event-tracing output.  

Only one tracing context can be created for the supplied context.  If you attempt to create additional tracing contexts for a context that's already being traced, no new context is created and DPSTraceContext() returns -1.

	RETURN	DPSTraceContext() returns 0 if successful in creating a tracing context, or -1 if not.  

NX_EVENTCODEMASK()

	SUMMARY	Generate an event mask for an event type

	DECLARED IN	dpsclient/event.h

	SYNOPSIS	int NX_EVENTCODEMASK(int type)

	DESCRIPTION	This handy utility macro returns an event mask that corresponds to the given (single) event type.