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NSDPSContext

Inherits From:
NSGraphicsContext : NSObject

Conforms To:
NSObject (NSObject)

Declared In:
AppKit/NSDPSContext.h

Class Description

The NSDPSContext class is the programmatic interface to objects that represent Display PostScript System contexts. A context can be thought of as a destination to which PostScript code is sent for execution. Each Display PostScript context contains its own complete PostScript environment including its own local VM (PostScript Virtual Memory). Every context has its own set of stacks, including an operand stack, graphics state stack, dictionary stack, and execution stack. Every context also contains a FontDirectory which is local to that context, plus a SharedFontDirectory that is shared across all contexts. There are three built-in dictionaries in the dictionary stack. From top to bottom, they are userdict, globaldict, and systemdict. userdict is private to the context, while globaldict and systemdict are shared by all contexts. globaldict is a modifiable dictionary containing information common to all contexts. systemdict is a read-only dictionary containing all the PostScript operators.

At any time there is the notion of the current context. The current context for the current thread may be set using setCurrentContext:.

NSDPSContext objects by default write their output to a specified data destination. This is used for printing, faxing, and for generation of saved EPS (Encapsulated PostScript) code. The means to create contexts that interact with displays are platform-specific.

The NSApplication object creates an NSDPSContext by default.

NSDPSContext Objects and Display PostScript System Context Records

When an NSDPSContext object is created, it creates and manages a DPSContext record. Programmers familiar with the client side C function interface to the Display PostScript System can access the DPSContext record by sending a context message to an NSDPSContext object. You can then operate on this context record using any of the functions or single operator functions defined in the Display PostScript System client library. Conversely, you can create an NSDPSContext object from a DPSContext record with the DPSContextObject function, as defined in "Client Library Functions". You can then work with the created NSDPSContext object using any of the methods described here.

General Exception Conditions

A variety of exceptions can be raised from NSDPSContext. In most cases, exceptions are raised because of errors returned from the Display PostScript Server. Exceptions are listed under "Types and Constants." Also see the Display PostScript System, Client Library Reference Manual, by Adobe Systems Incorporated, for more details on Display PostScript System error names and their possible causes.


Method Types

Initializing a context
- initWithMutableData:forDebugging:languageEncoding:nameEncoding:textProc:errorProc:
Testing the drawing destination
- isDrawingToScreen
Accessing context data
- mutableData
Setting and identifying the current context
+ currentContext
+ setCurrentContext:
- DPSContext
Controlling the context
- flush
- interruptExecution
- notifyObjectWhenFinishedExecuting:
- resetCommunication
- wait
Managing returned text and errors
+ stringForDPSError:
- errorProc
- setErrorProc:
- setTextProc:
- textProc
Sending raw data
- printFormat:
- printFormat:arguments:
- writeData:
- writePostScriptWithLanguageEncodingConversion:
Managing binary object sequences
- awaitReturnValues
- writeBOSArray:count:ofType:
- writeBOSNumString:length:ofType:scale:
- writeBOSString:length:
- writeBinaryObjectSequence:length:
- updateNameMap
Managing chained contexts
- chainChildContext:
- childContext
- parentContext
- unchainContext
Controlling the wait cursor
- startWaitCursorTimer
- setWaitCursorEnabled:
- isWaitCursorEnabled
Debugging aids
+ areAllContextsOutputTraced
+ areAllContextsSynchronized
+ setAllContextsOutputTraced:
+ setAllContextsSynchronized:
- isOutputTraced
- isSynchronized
- setOutputTraced:
- setSynchronized:

Class Methods

areAllContextsOutputTraced

+ (BOOL)areAllContextsOutputTraced

Returns YES if the data flowing between the application's contexts and their destinations is copied to diagnostic output.


areAllContextsSynchronized

+ (BOOL)areAllContextsSynchronized

Returns YES if all NSPDSContext objects invoke the wait method after sending each batch of output.


currentContext

+ (id)currentContext

Returns the id for the current context of the current thread.


setAllContextsOutputTraced:

+ (void)setAllContextsOutputTraced:(BOOL)flag

Causes the data (PostScript code, return values, and so forth) flowing between the all the application's contexts and their destinations to be copied to diagnostic output.


setAllContextsSynchronized:

+ (void)setAllContextsSynchronized:(BOOL)flag

Causes the wait method to be invoked each time an NSDPSContext object sends a batch of output to its destination.


setCurrentContext:

+ (void)setCurrentContext:(NSGraphicsContext *)context

Installs context as the current context of the current thread.


stringForDPSError:

+ (NSString *)stringForDPSError:(const DPSBinObjSeqRec *)error

Returns a string representation of error.


Instance Methods

DPSContext

- (DPSContext)DPSContext

Returns the corresponding DPScontext.


awaitReturnValues

- (void)awaitReturnValues

Waits for all return values from the result table.


chainChildContext:

- (void)chainChildContext:(NSDPSContext *)child

Links child (and all of it's children) to the receiver as its chained context, a context that receives a copy of all PostScript code sent to the receiver.


childContext

- (NSDPSContext *)childContext

Returns the receiver's child context, or nil if none exists.


errorProc

- (DPSErrorProc)errorProc

Returns the context's error callback function.


flush

- (void)flush

Forces any buffered data to be sent to its destination.


initWithMutableData:forDebugging:languageEncoding:nameEncoding:textProc:errorProc:

- initWithMutableData:(NSMutableData *)data
forDebugging:(BOOL)debug
languageEncoding(DPSProgramEncoding)langEnc
nameEncoding(DPSNameEncoding)nameEnc
textProc:(DPSTextProc)tProc
errorProc:(DPSErrorProc)errorProc

Initializes a newly allocated NSDPSContext that writes its output to data using the language and name encodings specified by langEnc and nameEnc. The callback functions tProc and errorProc handle text and errors generated by the context. If debug is YES, the output is given in human-readable form in which large structures (such as images) may be represented by comments.


interruptExecution

- (void)interruptExecution

Interrupts execution in the receiver's context.


isDrawingToScreen

- (BOOL)isDrawingToScreen

Returns YES if the drawing destination is the screen.


isOutputTraced

- (BOOL)isOutputTraced

Returns YES if the data flowing between the application's single context and its destination is copied to diagnostic output.


isSynchronized

- (BOOL)isSynchronized

Returns whether the wait method is invoked each time the receiver sends a batch of output to the server.


isWaitCursorEnabled

- (BOOL)isWaitCursorEnabled

Returns whether the wait cursor is enabled.


mutableData

- (NSMutableData *)mutableData

Returns the receiver's data object.


notifyObjectWhenFinishedExecuting:

- (void)notifyObjectWhenFinishedExecuting:(id)object

Registers object to receive a contextFinishedExecuting: message when the NSDPSContext's destination is ready to receive more input.


parentContext

- (NSDPSContext *)parentContext

Returns the receiver's parent context, or nil if none exists.


printFormat:

- (void)printFormat:(NSString *)format,...

Constructs a string from format and following string objects (in the manner of printf) and sends it to the context's destination.


printFormat:arguments:

- (void)printFormat:(NSString *)format
arguments:(va_list)argList

Constructs a string from format and argList (in the manner of vprintf) and sends it to the context's destination.


resetCommunication

- (void)resetCommunication

Discards any data that hasn't already been sent to its destination.


setErrorProc:

- (void)setErrorProc:(DPSErrorProc)proc

Sets the context's error callback function to proc.


setOutputTraced:

- (void)setOutputTraced:(BOOL)flag

Causes the data (PostScript code, return values, and so on) flowing between the application's single context and the Display PostScript server to be copied to diagnostic output.


setSynchronized:

- (void)setSynchronized:(BOOL)flag

Sets whether the wait method is invoked each time the receiver sends a batch of output to its destination.


setTextProc:

- (void)setTextProc:(DPSTextProc)proc

Sets the context's text callback function to proc.


setWaitCursorEnabled:

- (void)setWaitCursorEnabled:(BOOL)flag

Sets whether the wait cursor is enabled or disabled according to flag.

See also: PSsetwaitcursorenabled (function)


startWaitCursorTimer

- (void)startWaitCursorTimer

Generates a pseudo-event to start wait cursor timer.

See also: setWaitCursorEnabled:


textProc

- (DPSTextProc)textProc

Returns the context's text callback function.


unchainContext

- (void)unchainContext

Unlinks the child context (and all of it's children) from the receiver's list of chained contexts.


updateNameMap

- (void)updateNameMap

Updates the context's name map from the client library's name map.


wait

- (void)wait

Waits until the NSDPSContext's destination is ready to receive more input.


writeBOSArray:count:ofType:

- (void)writeBOSArray:(const void *)data
count:(unsigned int)items
ofType:(DPSDefinedType)type

Write an array to the context's destination as part of a binary object sequence. The array is taken from data and consists of items items of type type.


writeBOSNumString:length:ofType:scale:

- (void)writeBOSNumString:(const void *)data
length:(unsigned int)count
ofType(DPSDefinedType)type
scale:(int)scale

Write a number string to the context's destination as part of a binary object sequenc