 |
Index for
Section 3 |
|
 |
Alphabetical
listing for T |
|
 |
Bottom of
page |
|
ttmedia_ptype_declare(3)
CDE
NAME
ttmedia_ptype_declare - declare the ptype of a Media Exchange media editor
SYNOPSIS
#include <Tt/tttk.h>
Tt_status ttmedia_ptype_declare(const char *ptype,
int base_opnum,
Ttmedia_load_pat_cb cb,
void *clientdata,
int declare);
DESCRIPTION
The ttmedia_ptype_declare function is used to initialize an editor that
implements the Media Exchange message interface for a particular media
type. The ttmedia_ptype_declare function notifies the ToolTalk service that
the cb callback is to be called when the editor is asked to edit a document
of the kind supported by ptype. The ttmedia_ptype_declare function installs
an implementation-specific opnum callback on a series of signatures that
ptype is assumed to contain. These signatures are listed below, with their
corresponding opnum offsets. Opnums in ptype for these signatures start at
base_opnum, which must be zero or a multiple of 1000. The implementation-
specific opnum callback will pass clientdata to cb when a request is
received that matches one of these signatures.
If declare is True, ttmedia_ptype_declare calls ttmedia_ptype_declare with
the ptype argument. If ptype implements Media Exchange for several
different media types, then ttmedia_ptype_declare can be called multiple
times, with a different base_opnum each time, and with declare being True
only once.
The Ttmedia_load_pat_cb argument is a callback defined as:
Tt_message (*Ttmedia_load_pat_cb)(Tt_message msg,
void *clientdata,
Tttk_op op,
Tt_status diagnosis,
unsigned char *contents,
int len,
char *file,
char *docname);
The msg argument is a TT_REQUEST in Tt_state TT_SENT. The client program
becomes responsible for either failing, rejecting or replying to it. This
can either be done inside the callback, or the message can be saved and
dismissed later (that is, after the callback returns). Usually, the
callback will either immediately reject/fail the request, or it will start
processing the request, perhaps by associating it with a new window. When
the request is finally dismissed, it should be destroyed, for example,
using tt_message_destroy.
If the callback knows it will handle the request (either fail or reply to
it, but not reject it), then it should call ttdt_message_accept(3). But if
the return value of tt_message_status(3) of msg is TT_WRN_START_MESSAGE,
then the callback should probably do ttdt_session_join, and perhaps a
ttdt_file_join, before accepting the message. The op argument is the op of
the incoming request, one of TTME_COMPOSE, TTME_EDIT or TTME_DISPLAY. The
diagnosis argument is the recommended error code; if the ToolTalk service
detects a problem with the request (for example, TT_DESKTOP_ENODATA), then
it passes in the error code that it recommends the request should be failed
with. If diagnosis was not TT_OK and the Ttmedia_load_pat_cb returns msg,
then the ToolTalk service will fail and destroy msg.
The ToolTalk service does not simply fail the request transparently,
because the request may be the reason that the client process was started
by ToolTalk in the first place. So if diagnosis is not TT_OK and the
tt_message_status of msg is TT_WRN_START_MESSAGE, then many applications
will decide that they have no reason to continue running. If such an
application chooses to exit in the callback, then it should first dismiss
the request. Otherwise, it can set some global option, return msg (thus
allowing the ToolTalk service to dismiss the message), and then have main
check the option and exit before even entering the event loop. (Exiting
without dismissing the request would fail it with status TT_ERR_PROCID,
instead of with diagnostic).
The contents, len, and file arguments represent the contents of the
arriving document. If len is zero, then the document is contained in file.
If contents or file are non-NULL, they can be freed using tt_free.
The docname argument is the name of the document, if any. The clientdata
argument is the clientdata passed to ttmedia_ptype_declare.
A Ttmedia_load_pat_cb should return zero if it processes msg successfully,
or a tt_error_pointer cast to Tt_message if processing results in an error.
It should return the msg if it does not consume it. If diagnosis is not
TT_OK and msg is returned, then the ToolTalk service will consume (namely,
fail and destroy) it. If diagnosis is TT_OK and msg is returned, then the
ToolTalk service will pass TT_CALLBACK_CONTINUE down the call stack, so
that msg will be offered to other callbacks or (more likely) be returned
from tt_message_receive(3). Applications will rarely want msg to get
processed by other callbacks or in the main event loop.
RETURN VALUE
Upon successful completion, the ttmedia_ptype_declare function returns the
status of the operation. The application can use tt_ptr_error(3) to extract
one of the following Tt_status values from the returned handle:
TT_OK
The operation completed successfully.
TT_ERR_NOMP
The ttsession(1) process is not running and the ToolTalk service cannot
restart it.
TT_ERR_POINTER
The pointer passed does not point to an object of the correct type for
this operation.
TT_ERR_PROCID
The specified process identifier is out of date or invalid.
TT_ERR_PTYPE
The specified process type is not the name of an installed process
type.
EXAMPLES
This is the typical algorithm of a Ttmedia_load_pat_cb:
Tt_message
myAcmeSheetLoadCB(
Tt_message msg,
void *client_data,
Tttk_op op,
Tt_status diagnosis,
unsigned char *contents,
int len,
char *file,
char *docname
)
{
Tt_status status = TT_OK;
if (diagnosis != TT_OK) {
/* toolkit detected an error */
if (tt_message_status(msg) == TT_WRN_START_MESSAGE) {
/*
* Error is in start message! We now have no
* reason to live, so tell main() to exit().
*/
myAbortCode = 2;
}
/* let toolkit handle the error */
return msg;
}
if ((op == TTME_COMPOSE)&&(file == 0)) {
/* open empty new buffer */
} else if (len > 0) {
/* load contents into new buffer */
} else if (file != 0) {
if (ttdt_Get_Modified(msg, file, TT_BOTH, myCntxt, 5000)) {
switch(myUserChoice("Save, Revert, Ignore?")) {
case 0:
ttdt_Save(msg, file, TT_BOTH, myCntxt, 5000);
break;
case 1:
ttdt_Revert(msg, file, TT_BOTH, myCntxt, 5000);
break;
}
}
/* load file into new buffer */
} else {
tttk_message_fail(msg, TT_DESKTOP_ENODATA, 0, 1);
tt_free(contents); tt_free(file); tt_free(docname);
return 0;
}
int w, h, x, y = INT_MAX;
ttdt_sender_imprint_on(0, msg, 0, &w, &h, &x, &y, myCntxt, 5000);
positionMyWindowRelativeTo(w, h, x, y);
if (maxBuffersAreNowOpen) {
/* Un-volunteer to handle future requests until less busy */
tt_ptype_undeclare("Acme_Calc");
}
if (tt_message_status(msg) == TT_WRN_START_MESSAGE) {
/*
* Join session before accepting start message,
* to prevent unnecessary starts of our ptype
*/
ttdt_session_join(0, myContractCB, myShell, 0, 1);
}
ttdt_message_accept(msg, myContractCB, myShell, 0, 1, 1);
tt_free(contents); tt_free(file); tt_free(docname);
return 0;
}
This is the signature layout to which ptype should conform:
ptype Acme_Calc {
start "acalc";
handle:
/*
* Instantiate Acme_Sheet
* Include in tool's ptype if tool can be a document factory.
*/
session Instantiate(in Acme_Sheet template) => start opnum = 401;
/*
* Display Acme_Sheet
* Include in tool's ptype if tool can display a document.
*/
session Display(in Acme_Sheet contents) => start opnum = 1;
session Display(in Acme_Sheet contents,
in messageID counterfoil) => start opnum = 2;
session Display(in Acme_Sheetcontents,
in title docName) => start opnum = 3;
session Display(in Acme_Sheet contents,
in messageID counterfoil,
in title docName) => start opnum = 4;
/*
* Edit Acme_Sheet
* Include in tool's ptype if tool can edit a document.
*/
session Edit(inout Acme_Sheet contents) => start opnum = 101;
session Edit(inout Acme_Sheet contents,
in messageID counterfoil) => start opnum = 102;
session Edit(inout Acme_Sheet contents,
in title docName) => start opnum = 103;
session Edit(inout Acme_Sheet contents,
in messageID counterfoil,
in title docName) => start opnum = 104;
/*
* Compose Acme_Sheet
* Include in tool's ptype if tool can compose a
* document from scratch.
*/
session Edit(out Acme_Sheet contents) => start opnum = 201;
session Edit(out Acme_Sheet contents,
in messageID counterfoil) => start opnum = 202;
session Edit(out Acme_Sheet contents,
in title docName) => start opnum = 203;
session Edit(out Acme_Sheet contents,
in messageID counterfoil,
in title docName) => start opnum = 204;
/*
* Mail Acme_Sheet
* Include in tool's ptype if tool can mail a document.
*/
session Mail(in Acme_Sheet contents) => start opnum = 301;
session Mail(inout Acme_Sheet contents) => start opnum = 311;
session Mail(inout Acme_Sheet contents,
in title docName) => start opnum = 313;
session Mail(out Acme_Sheet contents) => start opnum = 321;
session Mail(out Acme_Sheet contents,
in messageID counterfoil) => start opnum = 323;
};
SEE ALSO
Tttttk(5), tt_ptype_declare(3), tt_ptype_undeclare(3),
ttdt_message_accept(3), ttdt_session_join(3), ttdt_file_join(3),
tt_free(3), tt_message_receive(3)
|
Index for
Section 3 |
|
|
Alphabetical
listing for T |
|
 |
Top of
page |
|