man/man3/Tk_CreateErrorHandler.3 - toolchains/skids - Git at Google

 '\"
 '\" Copyright (c) 1990 The Regents of the University of California.
 '\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
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 '\" See the file "license.terms" for information on usage and redistribution
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 '\" RCS: @(#) $Id: CrtErrHdlr.3,v 1.2 1998/09/14 18:22:46 stanton Exp $
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 '\" The definitions below are for supplemental macros used in Tcl/Tk
 '\" manual entries.
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 '\" .AP type name in/out ?indent?
 '\"	Start paragraph describing an argument to a library procedure.
 '\"	type is type of argument (int, etc.), in/out is either "in", "out",
 '\"	or "in/out" to describe whether procedure reads or modifies arg,
 '\"	and indent is equivalent to second arg of .IP (shouldn't ever be
 '\"	needed;  use .AS below instead)
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 '\" .AS ?type? ?name?
 '\"	Give maximum sizes of arguments for setting tab stops.  Type and
 '\"	name are examples of largest possible arguments that will be passed
 '\"	to .AP later.  If args are omitted, default tab stops are used.
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 '\" .BS
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 '\"	options follow on successive lines, in four columns separated
 '\"	by tabs.
 '\"
 '\" .SE
 '\"	End of list of standard options for a Tk widget.
 '\"
 '\" .OP cmdName dbName dbClass
 '\"	Start of description of a specific option.  cmdName gives the
 '\"	option's name as specified in the class command, dbName gives
 '\"	the option's name in the option database, and dbClass gives
 '\"	the option's class in the option database.
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 '\" .UL arg1 arg2
 '\"	Print arg1 underlined, then print arg2 normally.
 '\"
 '\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $
 '\"
 '\"	# Set up traps and other miscellaneous stuff for Tcl/Tk man pages.
 .if t .wh -1.3i ^B
 .nr ^l \n(.l
 .ad b
 '\"	# Start an argument description
 .de AP
 .ie !"\\$4"" .TP \\$4
 .el \{\
 .   ie !"\\$2"" .TP \\n()Cu
 .   el          .TP 15
 .\}
 .ta \\n()Au \\n()Bu
 .ie !"\\$3"" \{\
 \&\\$1	\\fI\\$2\\fP	(\\$3)
 .\".b
 .\}
 .el \{\
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 ..
 .AS Tcl_Interp Tcl_CreateInterp in/out
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 .\}
 .el \}\
 \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
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 .LP
 See the \\fBoptions\\fR manual entry for details on the standard options.
 ..
 '\"	# OP - start of full description for a single option
 .de OP
 .LP
 .nf
 .ta 4c
 Command-Line Name:	\\fB\\$1\\fR
 Database Name:	\\fB\\$2\\fR
 Database Class:	\\fB\\$3\\fR
 .fi
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 ..
 .TH Tk_CreateErrorHandler 3 "" Tk "Tk Library Procedures"
 .BS
 .SH NAME
 Tk_CreateErrorHandler, Tk_DeleteErrorHandler \- handle X protocol errors
 .SH SYNOPSIS
 .nf
 \fB#include <tk.h>\fR
 .sp
 Tk_ErrorHandler
 \fBTk_CreateErrorHandler\fR(\fIdisplay, error, request, minor, proc, clientData\fR)
 .sp
 \fBTk_DeleteErrorHandler\fR(\fIhandler\fR)
 .SH ARGUMENTS
 .AS "Tk_ErrorHandler" clientData
 .AP Display *display in
 Display whose errors are to be handled.
 .AP int error in
 Match only error events with this value in the \fIerror_code\fR
 field.  If -1, then match any \fIerror_code\fR value.
 .AP int request in
 Match only error events with this value in the \fIrequest_code\fR
 field.  If -1, then match any \fIrequest_code\fR value.
 .AP int minor in
 Match only error events with this value in the \fIminor_code\fR
 field.  If -1, then match any \fIminor_code\fR value.
 .AP Tk_ErrorProc *proc in
 Procedure to invoke whenever an error event is received for
 \fIdisplay\fR and matches \fIerror\fR, \fIrequest\fR, and \fIminor\fR.
 NULL means ignore any matching errors.
 .AP ClientData clientData in
 Arbitrary one-word value to pass to \fIproc\fR.
 .AP Tk_ErrorHandler handler in
 Token for error handler to delete (return value from a previous
 call to \fBTk_CreateErrorHandler\fR).
 .BE

 .SH DESCRIPTION
 .PP
 \fBTk_CreateErrorHandler\fR arranges for a particular procedure
 (\fIproc\fR) to be called whenever certain protocol errors occur on a
 particular display (\fIdisplay\fR).  Protocol errors occur when
 the X protocol is used incorrectly, such as attempting to map a window
 that doesn't exist.  See the Xlib documentation for \fBXSetErrorHandler\fR
 for more information on the kinds of errors that can occur.
 For \fIproc\fR to be invoked
 to handle a particular error, five things must occur:
 .IP [1]
 The error must pertain to \fIdisplay\fR.
 .IP [2]
 Either the \fIerror\fR argument to \fBTk_CreateErrorHandler\fR
 must have been -1, or the \fIerror\fR argument must match
 the \fIerror_code\fR field from the error event.
 .IP [3]
 Either the \fIrequest\fR argument to \fBTk_CreateErrorHandler\fR
 must have been -1, or the \fIrequest\fR argument must match
 the \fIrequest_code\fR field from the error event.
 .IP [4]
 Either the \fIminor\fR argument to \fBTk_CreateErrorHandler\fR
 must have been -1, or the \fIminor\fR argument must match
 the \fIminor_code\fR field from the error event.
 .IP [5]
 The protocol request to which the error pertains must have been
 made when the handler was active (see below for more information).
 .PP
 \fIProc\fR should have arguments and result that match the
 following type:
 .CS
 typedef int Tk_ErrorProc(
 	ClientData \fIclientData\fR,
 	XErrorEvent *\fIerrEventPtr\fR);
 .CE
 The \fIclientData\fR parameter to \fIproc\fR is a copy of the \fIclientData\fR
 argument given to \fBTcl_CreateErrorHandler\fR when the callback
 was created.  Typically, \fIclientData\fR points to a data
 structure containing application-specific information that is
 needed to deal with the error.  \fIErrEventPtr\fR is
 a pointer to the X error event.
 The procedure \fIproc\fR should return an integer value.  If it
 returns 0 it means that \fIproc\fR handled the error completely and there
 is no need to take any other action for the error.  If it returns
 non-zero it means \fIproc\fR was unable to handle the error.
 .PP
 If a value of NULL is specified for \fIproc\fR, all matching errors
 will be ignored:  this will produce the same result as if a procedure
 had been specified that always returns 0.
 .PP
 If more than more than one handler matches a particular error, then
 they are invoked in turn.  The handlers will be invoked in reverse
 order of creation:  most recently declared handler first.
 If any handler returns 0, then subsequent (older) handlers will
 not be invoked.  If no handler returns 0, then Tk invokes X'es
 default error handler, which prints an error message and aborts the
 program.  If you wish to have a default handler that deals with errors
 that no other handler can deal with, then declare it first.
 .PP
 The X documentation states that ``the error handler should not call
 any functions (directly or indirectly) on the display that will
 generate protocol requests or that will look for input events.''
 This restriction applies to handlers declared by \fBTk_CreateErrorHandler\fR;
 disobey it at your own risk.
 .PP
 \fBTk_DeleteErrorHandler\fR may be called to delete a
 previously-created error handler.  The \fIhandler\fR argument
 identifies the error handler, and should be a value returned by
 a previous call to \fBTk_CreateEventHandler\fR.
 .PP
 A particular error handler applies to errors resulting
 from protocol requests generated between
 the call to \fBTk_CreateErrorHandler\fR and the call to
 \fBTk_DeleteErrorHandler\fR.  However, the actual callback
 to \fIproc\fR may not occur until after the \fBTk_DeleteErrorHandler\fR
 call, due to buffering in the client and server.
 If an error event pertains to
 a protocol request made just before calling \fBTk_DeleteErrorHandler\fR,
 then the error event may not have been processed
 before the \fBTk_DeleteErrorHandler\fR
 call.  When this situation arises, Tk will save information about
 the handler and
 invoke the handler's \fIproc\fR later when the error event
 finally arrives.
 If an application wishes to delete an error handler and know
 for certain that all relevant errors have been processed,
 it should first call \fBTk_DeleteErrorHandler\fR and then
 call \fBXSync\fR;  this will flush out any buffered requests and errors,
 but will result in a performance penalty because
 it requires communication to and from the X server.  After the
 \fBXSync\fR call Tk is guaranteed not to call any error
 handlers deleted before the \fBXSync\fR call.
 .PP
 For the Tk error handling mechanism to work properly, it is essential
 that application code never calls \fBXSetErrorHandler\fR directly;
 applications should use only \fBTk_CreateErrorHandler\fR.

 .SH KEYWORDS
 callback, error, event, handler
	'\"
	'\" Copyright (c) 1990 The Regents of the University of California.
	'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
	'\"
	'\" See the file "license.terms" for information on usage and redistribution
	'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
	'\"
	'\" RCS: @(#) $Id: CrtErrHdlr.3,v 1.2 1998/09/14 18:22:46 stanton Exp $
	'\"
	'\" The definitions below are for supplemental macros used in Tcl/Tk
	'\" manual entries.
	'\"
	'\" .AP type name in/out ?indent?
	'\" Start paragraph describing an argument to a library procedure.
	'\" type is type of argument (int, etc.), in/out is either "in", "out",
	'\" or "in/out" to describe whether procedure reads or modifies arg,
	'\" and indent is equivalent to second arg of .IP (shouldn't ever be
	'\" needed; use .AS below instead)
	'\"
	'\" .AS ?type? ?name?
	'\" Give maximum sizes of arguments for setting tab stops. Type and
	'\" name are examples of largest possible arguments that will be passed
	'\" to .AP later. If args are omitted, default tab stops are used.
	'\"
	'\" .BS
	'\" Start box enclosure. From here until next .BE, everything will be
	'\" enclosed in one large box.
	'\"
	'\" .BE
	'\" End of box enclosure.
	'\"
	'\" .CS
	'\" Begin code excerpt.
	'\"
	'\" .CE
	'\" End code excerpt.
	'\"
	'\" .VS ?version? ?br?
	'\" Begin vertical sidebar, for use in marking newly-changed parts
	'\" of man pages. The first argument is ignored and used for recording
	'\" the version when the .VS was added, so that the sidebars can be
	'\" found and removed when they reach a certain age. If another argument
	'\" is present, then a line break is forced before starting the sidebar.
	'\"
	'\" .VE
	'\" End of vertical sidebar.
	'\"
	'\" .DS
	'\" Begin an indented unfilled display.
	'\"
	'\" .DE
	'\" End of indented unfilled display.
	'\"
	'\" .SO
	'\" Start of list of standard options for a Tk widget. The
	'\" options follow on successive lines, in four columns separated
	'\" by tabs.
	'\"
	'\" .SE
	'\" End of list of standard options for a Tk widget.
	'\"
	'\" .OP cmdName dbName dbClass
	'\" Start of description of a specific option. cmdName gives the
	'\" option's name as specified in the class command, dbName gives
	'\" the option's name in the option database, and dbClass gives
	'\" the option's class in the option database.
	'\"
	'\" .UL arg1 arg2
	'\" Print arg1 underlined, then print arg2 normally.
	'\"
	'\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $
	'\"
	'\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages.
	.if t .wh -1.3i ^B
	.nr ^l \n(.l
	.ad b
	'\" # Start an argument description
	.de AP
	.ie !"\\$4"" .TP \\$4
	.el \{\
	. ie !"\\$2"" .TP \\n()Cu
	. el .TP 15
	.\}
	.ta \\n()Au \\n()Bu
	.ie !"\\$3"" \{\
	\&\\$1 \\fI\\$2\\fP (\\$3)
	.\".b
	.\}
	.el \{\
	.br
	.ie !"\\$2"" \{\
	\&\\$1 \\fI\\$2\\fP
	.\}
	.el \{\
	\&\\fI\\$1\\fP
	.\}
	.\}
	..
	'\" # define tabbing values for .AP
	.de AS
	.nr )A 10n
	.if !"\\$1"" .nr )A \\w'\\$1'u+3n
	.nr )B \\n()Au+15n
	.\"
	.if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n
	.nr )C \\n()Bu+\\w'(in/out)'u+2n
	..
	.AS Tcl_Interp Tcl_CreateInterp in/out
	'\" # BS - start boxed text
	'\" # ^y = starting y location
	'\" # ^b = 1
	.de BS
	.br
	.mk ^y
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	.if n \l'\\n(.lu\(ul'
	.if n .fi
	..
	'\" # BE - end boxed text (draw box now)
	.de BE
	.nf
	.ti 0
	.mk ^t
	.ie n \l'\\n(^lu\(ul'
	.el \{\
	.\" Draw four-sided box normally, but don't draw top of
	.\" box if the box started on an earlier page.
	.ie !\\n(^b-1 \{\
	\h'-1.5n'\L'\|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'\|0u-1.5n\(ul'
	.\}
	.el \}\
	\h'-1.5n'\L'\|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'\|0u-1.5n\(ul'
	.\}
	.\}
	.fi
	.br
	.nr ^b 0
	..
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	'\" # ^Y = starting y location
	'\" # ^v = 1 (for troff; for nroff this doesn't matter)
	.de VS
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	.el .nr ^v 1u
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	.de VE
	.ie n 'mc
	.el \{\
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	\h'\|\\n(^lu+3n'\L'\|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-\|\\n(^lu+3n'
	.sp -1
	.fi
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	.\}
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	'\" # box/sidebar if in box/sidebar mode, then invoked standard
	'\" # page bottom macro.
	.de ^B
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	'ti 0
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	.mk ^t
	.if \\n(^b \{\
	.\" Draw three-sided box if this is the box's first page,
	.\" draw two sides but no top otherwise.
	.ie !\\n(^b-1 \h'-1.5n'\L'\|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\h'\|0u'\c
	.el \h'-1.5n'\L'\|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'\|0u'\c
	.\}
	.if \\n(^v \{\
	.nr ^x \\n(^tu+1v-\\n(^Yu
	\kx\h'-\\nxu'\h'\|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'\|0u'\c
	.\}
	.bp
	'fi
	.ev
	.if \\n(^b \{\
	.mk ^y
	.nr ^b 2
	.\}
	.if \\n(^v \{\
	.mk ^Y
	.\}
	..
	'\" # DS - begin display
	.de DS
	.RS
	.nf
	.sp
	..
	'\" # DE - end display
	.de DE
	.fi
	.RE
	.sp
	..
	'\" # SO - start of list of standard options
	.de SO
	.SH "STANDARD OPTIONS"
	.LP
	.nf
	.ta 5.5c 11c
	.ft B
	..
	'\" # SE - end of list of standard options
	.de SE
	.fi
	.ft R
	.LP
	See the \\fBoptions\\fR manual entry for details on the standard options.
	..
	'\" # OP - start of full description for a single option
	.de OP
	.LP
	.nf
	.ta 4c
	Command-Line Name: \\fB\\$1\\fR
	Database Name: \\fB\\$2\\fR
	Database Class: \\fB\\$3\\fR
	.fi
	.IP
	..
	'\" # CS - begin code excerpt
	.de CS
	.RS
	.nf
	.ta .25i .5i .75i 1i
	..
	'\" # CE - end code excerpt
	.de CE
	.fi
	.RE
	..
	.de UL
	\\$1\l'\|0\(ul'\\$2
	..
	.TH Tk_CreateErrorHandler 3 "" Tk "Tk Library Procedures"
	.BS
	.SH NAME
	Tk_CreateErrorHandler, Tk_DeleteErrorHandler \- handle X protocol errors
	.SH SYNOPSIS
	.nf
	\fB#include <tk.h>\fR
	.sp
	Tk_ErrorHandler
	\fBTk_CreateErrorHandler\fR(\fIdisplay, error, request, minor, proc, clientData\fR)
	.sp
	\fBTk_DeleteErrorHandler\fR(\fIhandler\fR)
	.SH ARGUMENTS
	.AS "Tk_ErrorHandler" clientData
	.AP Display *display in
	Display whose errors are to be handled.
	.AP int error in
	Match only error events with this value in the \fIerror_code\fR
	field. If -1, then match any \fIerror_code\fR value.
	.AP int request in
	Match only error events with this value in the \fIrequest_code\fR
	field. If -1, then match any \fIrequest_code\fR value.
	.AP int minor in
	Match only error events with this value in the \fIminor_code\fR
	field. If -1, then match any \fIminor_code\fR value.
	.AP Tk_ErrorProc *proc in
	Procedure to invoke whenever an error event is received for
	\fIdisplay\fR and matches \fIerror\fR, \fIrequest\fR, and \fIminor\fR.
	NULL means ignore any matching errors.
	.AP ClientData clientData in
	Arbitrary one-word value to pass to \fIproc\fR.
	.AP Tk_ErrorHandler handler in
	Token for error handler to delete (return value from a previous
	call to \fBTk_CreateErrorHandler\fR).
	.BE

	.SH DESCRIPTION
	.PP
	\fBTk_CreateErrorHandler\fR arranges for a particular procedure
	(\fIproc\fR) to be called whenever certain protocol errors occur on a
	particular display (\fIdisplay\fR). Protocol errors occur when
	the X protocol is used incorrectly, such as attempting to map a window
	that doesn't exist. See the Xlib documentation for \fBXSetErrorHandler\fR
	for more information on the kinds of errors that can occur.
	For \fIproc\fR to be invoked
	to handle a particular error, five things must occur:
	.IP [1]
	The error must pertain to \fIdisplay\fR.
	.IP [2]
	Either the \fIerror\fR argument to \fBTk_CreateErrorHandler\fR
	must have been -1, or the \fIerror\fR argument must match
	the \fIerror_code\fR field from the error event.
	.IP [3]
	Either the \fIrequest\fR argument to \fBTk_CreateErrorHandler\fR
	must have been -1, or the \fIrequest\fR argument must match
	the \fIrequest_code\fR field from the error event.
	.IP [4]
	Either the \fIminor\fR argument to \fBTk_CreateErrorHandler\fR
	must have been -1, or the \fIminor\fR argument must match
	the \fIminor_code\fR field from the error event.
	.IP [5]
	The protocol request to which the error pertains must have been
	made when the handler was active (see below for more information).
	.PP
	\fIProc\fR should have arguments and result that match the
	following type:
	.CS
	typedef int Tk_ErrorProc(
	ClientData \fIclientData\fR,
	XErrorEvent *\fIerrEventPtr\fR);
	.CE
	The \fIclientData\fR parameter to \fIproc\fR is a copy of the \fIclientData\fR
	argument given to \fBTcl_CreateErrorHandler\fR when the callback
	was created. Typically, \fIclientData\fR points to a data
	structure containing application-specific information that is
	needed to deal with the error. \fIErrEventPtr\fR is
	a pointer to the X error event.
	The procedure \fIproc\fR should return an integer value. If it
	returns 0 it means that \fIproc\fR handled the error completely and there
	is no need to take any other action for the error. If it returns
	non-zero it means \fIproc\fR was unable to handle the error.
	.PP
	If a value of NULL is specified for \fIproc\fR, all matching errors
	will be ignored: this will produce the same result as if a procedure
	had been specified that always returns 0.
	.PP
	If more than more than one handler matches a particular error, then
	they are invoked in turn. The handlers will be invoked in reverse
	order of creation: most recently declared handler first.
	If any handler returns 0, then subsequent (older) handlers will
	not be invoked. If no handler returns 0, then Tk invokes X'es
	default error handler, which prints an error message and aborts the
	program. If you wish to have a default handler that deals with errors
	that no other handler can deal with, then declare it first.
	.PP
	The X documentation states that ``the error handler should not call
	any functions (directly or indirectly) on the display that will
	generate protocol requests or that will look for input events.''
	This restriction applies to handlers declared by \fBTk_CreateErrorHandler\fR;
	disobey it at your own risk.
	.PP
	\fBTk_DeleteErrorHandler\fR may be called to delete a
	previously-created error handler. The \fIhandler\fR argument
	identifies the error handler, and should be a value returned by
	a previous call to \fBTk_CreateEventHandler\fR.
	.PP
	A particular error handler applies to errors resulting
	from protocol requests generated between
	the call to \fBTk_CreateErrorHandler\fR and the call to
	\fBTk_DeleteErrorHandler\fR. However, the actual callback
	to \fIproc\fR may not occur until after the \fBTk_DeleteErrorHandler\fR
	call, due to buffering in the client and server.
	If an error event pertains to
	a protocol request made just before calling \fBTk_DeleteErrorHandler\fR,
	then the error event may not have been processed
	before the \fBTk_DeleteErrorHandler\fR
	call. When this situation arises, Tk will save information about
	the handler and
	invoke the handler's \fIproc\fR later when the error event
	finally arrives.
	If an application wishes to delete an error handler and know
	for certain that all relevant errors have been processed,
	it should first call \fBTk_DeleteErrorHandler\fR and then
	call \fBXSync\fR; this will flush out any buffered requests and errors,
	but will result in a performance penalty because
	it requires communication to and from the X server. After the
	\fBXSync\fR call Tk is guaranteed not to call any error
	handlers deleted before the \fBXSync\fR call.
	.PP
	For the Tk error handling mechanism to work properly, it is essential
	that application code never calls \fBXSetErrorHandler\fR directly;
	applications should use only \fBTk_CreateErrorHandler\fR.

	.SH KEYWORDS
	callback, error, event, handler