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.TH XpGetDocumentData 3Xp __xorgversion__ "XPRINT FUNCTIONS"
.SH NAME
XpGetDocumentData \- Creates and initializes a new print context.
.SH SYNOPSIS
.br
cc [ flag... ] file... -lXp [ library... ]
.br
#include <X11/extensions/Print.h>
.LP
.B Status XpGetDocumentData
(
.I data_display,
.I context,
.I save_proc,
.I finish_proc,
.I client_data
)
.br
Display *\fIdata_display\fP\^;
.br
XPContext \fIcontext\fP\^;
.br
XPSaveProc \fIsave_proc\fP\^;
.br
XPFinishProc \fIfinish_proc\fP\^;
.br
XPointer \fIclient_data\fP\^;
.if n .ti +5n
.if t .ti +.5i
.SH ARGUMENTS
.TP
.I data_display
Specifies a pointer to the Display structure; returned from XOpenDisplay.
.TP
.I context
The print context from which document data is to be retrieved.
.TP
.I save_proc
A procedure to be registered and called repeatedly to save blocks of document
data.
.TP
.I finish_proc
A procedure to be registered and called once when the print job has completed
and
all document data has been sent to save_proc.
.TP
.I client_data
Specifies client data to be passed to save_proc and finish_proc when called.
.SH DESCRIPTION
.LP
XpGetDocumentData registers callbacks that allow a "consumer" to continuously
retrieve document data generated in the
.I X Print Server
by a separate "producer",
where both are referencing the same print context by way of
.I different
display
connections. Though XpGetDocumentData retrieves document data, its effect is
bounded by XpStartJob and XpEndJob. XpGetDocumentData always returns
immediately;
if an error occurs and the callbacks cannot be registered, the return status is
0,
else the return status is non-zero and the callbacks will be called sometime
after
the return from XpGetDocumentData. This producer/consumer exchange is set up
when
XpStartJob is called by the producer with output_mode equal XPGetData, and is
subsequently initiated when XpGetDocumentData is called by the consumer. Though
XpStartJob will return immediately, further attempts to use the producer's
display
connection may be blocked by the
.I X Print Server
until XpGetDocumentData is called on the consumer's display connection.
Following a successful call to
.I XpGetDocumentData,
the consumer must enter a loop to process events from the server, for example,
by calling XNextEvent. The event processing code will invoke save_proc and
finish_proc as needed to consume incoming data. To avoid blocking indefinitely
in XNextEvent, the consumer should select for XPPrintNotify events, and watch
for XPEndJobNotify. This event will be sent following the call to finish_proc
and the consumer can safely exit the loop at this point. Aside from this
processing of XPrintNotify events, data_display must not be used for any
additional X requests until finish_proc is called and returns.
.SH STRUCTURES
The save_proc is defined in <X11/extensions/Print.h> as:
.LP
.nf
typedef void (*XPSaveProc)( Display *data_display,
XPContext context,
unsigned char *data,
unsigned int data_len,
XPointer client_data);
.fi
.LP
The save_proc is repeatedly called on each chunk of document data sent by the X
Print Server until either XpEndJob or XpCancelJob is called. data_len specifies
the number of bytes in data. The memory for data itself is owned by the library,
so save_proc should copy data to another location before returning. After the
last block of data has been delivered to save_proc, finish_proc is called with
final status.
The finish_proc is defined in <X11/extensions/Print.h> as:
.LP
.nf
typedef void (*XPFinishProc)( Display *data_display,
XPContext context,
XPGetDocStatus status,
XPointer client_data);
.fi
.LP
After XpGetDocumentData successfully registers the callbacks, any generated X
errors (for example, BadAlloc) or Xp errors (for example, XPBadContext or
XPBadSequence) that are the result of XpGetDocumentData will cause the Xlib
error handler to be invoked, and then will cause finish_proc to be called with a
status of XPGetDocError. Any other activities (for example, a separate process
destroying the print context) that prove fatal to the progress of
XpGetDocumentData will also cause finish_proc to be called with a status of
XPGetDocError.
If XpGetDocumentData is called prior to XpStartJob, then an XPBadSequence error
is generated and finish_proc is called with XPGetDocError. If XpGetDocumentData
is called after XpStartJob and output_mode was specified as XPSpool, then an
XPBadSequence error is generated and finish_proc is called with XPGetDocError.
If the producer starts generating data and the consumer cannot consume data
quickly enough, then the producer's display connection will be blocked by the
.I X Print Server.
Until XpEndJob or XpCancelJob is called, it is possible that various
XPPrintNotify events will be generated (for example, a page has been canceled).
The data passed to save_proc is not necessarily organized according to the
consumer's requests or any generated events, and its consistency is guaranteed
only if the entire job completes successfully (i.e. without being canceled or
generating an error).
When finish_proc is called, sometime after XpGetDocumentData is called and
returns, status gives the completion status of the job and is defined in
<X11/extensions/Print.h> as:
.LP
.nf
#define XPGetDocFinished 0 /\(** normal termination */
#define XPGetDocSecondConsumer 1 /\(** setup error */
#define XPGetDocError 2 /\(** progress error */
.fi
.LP
XPGetDocFinished indicates that all intended document data has been delivered by
way of save_proc. All cancellation events are guaranteed to have arrived by the
time finished_proc is called, and they should be taken into consideration for
evaluating the validity of the document data returned.
XPGetDocSecondConsumer indicates that a consumer had already been established
for the print context. The
.I X Print Server
only supports one consumer per print context.
XPGetDocError indicates that an error has been generated (for example,
XPBadContext or XPBadSequence) and that no further document data will be
delivered by the
.I X Print Server
to save_proc.
After finish_proc returns, save_proc and finish_proc are unregistered and will
no longer be called.
.SH DIAGNOSTICS
.TP 15
.SM XPBadContext
A valid print context-id has not been set prior to making this call.
.TP 15
.SM XPBadSequence
The function was not called in the proper order with respect to the other X
Print Service Extension calls (for example, XpGetDocumentData prior to
XpStartJob).
.SH "SEE ALSO"
.BR XpCancelJob (3Xp),
.BR XpEndJob (3Xp),
.BR XpStartJob (3Xp)
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