'\"
'\" Copyright (c) 1990-1994 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: after.n,v 1.1.1.1 2007/07/10 15:04:23 duncan 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 1.1.1.1 2007/07/10 15:04:23 duncan 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
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\&\\$1	\\fI\\$2\\fP	(\\$3)
.\".b
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.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
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'\"	# ^y = starting y location
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.mk ^y
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.if n \l'\\n(.lu\(ul'
.if n .fi
..
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.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
..
'\"	# VS - start vertical sidebar
'\"	# ^Y = starting y location
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.de VS
.if !"\\$2"" .br
.mk ^Y
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..
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.ev
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.nr ^v 0
..
'\"	# Special macro to handle page bottom:  finish off current
'\"	# box/sidebar if in box/sidebar mode, then invoked standard
'\"	# page bottom macro.
.de ^B
.ev 2
'ti 0
'nf
.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
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..
'\"	# 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
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..
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..
.de UL
\\$1\l'|0\(ul'\\$2
..
.TH after n 7.5 Tcl "Tcl Built-In Commands"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
after \- Execute a command after a time delay
.SH SYNOPSIS
\fBafter \fIms\fR
.sp
\fBafter \fIms \fR?\fIscript script script ...\fR?
.sp
\fBafter cancel \fIid\fR
.sp
\fBafter cancel \fIscript script script ...\fR
.sp
\fBafter idle \fR?\fIscript script script ...\fR?
.sp
\fBafter info \fR?\fIid\fR?
.BE

.SH DESCRIPTION
.PP
This command is used to delay execution of the program or to execute
a command in background sometime in the future.  It has several forms,
depending on the first argument to the command:
.TP
\fBafter \fIms\fR
\fIMs\fR must be an integer giving a time in milliseconds.
The command sleeps for \fIms\fR milliseconds and then returns.
While the command is sleeping the application does not respond to
events.
.TP
\fBafter \fIms \fR?\fIscript script script ...\fR?
In this form the command returns immediately, but it arranges
for a Tcl command to be executed \fIms\fR milliseconds later as an
event handler.
The command will be executed exactly once, at the given time.
The delayed command is formed by concatenating all the \fIscript\fR
arguments in the same fashion as the \fBconcat\fR command.
The command will be executed at global level (outside the context
of any Tcl procedure).
If an error occurs while executing the delayed command then the
\fBbgerror\fR mechanism is used to report the error.
The \fBafter\fR command returns an identifier that can be used
to cancel the delayed command using \fBafter cancel\fR.
.TP
\fBafter cancel \fIid\fR
Cancels the execution of a delayed command that
was previously scheduled.
\fIId\fR indicates which command should be canceled;  it must have
been the return value from a previous \fBafter\fR command.
If the command given by \fIid\fR has already been executed then
the \fBafter cancel\fR command has no effect.
.TP
\fBafter cancel \fIscript script ...\fR
This command also cancels the execution of a delayed command.
The \fIscript\fR arguments are concatenated together with space
separators (just as in the \fBconcat\fR command).
If there is a pending command that matches the string, it is
cancelled and will never be executed;  if no such command is
currently pending then the \fBafter cancel\fR command has no effect.
.TP
\fBafter idle \fIscript \fR?\fIscript script ...\fR?
Concatenates the \fIscript\fR arguments together with space
separators (just as in the \fBconcat\fR command), and arranges
for the resulting script to be evaluated later as an idle callback.
The script will be run exactly once, the next time the event
loop is entered and there are no events to process.
The command returns an identifier that can be used
to cancel the delayed command using \fBafter cancel\fR.
If an error occurs while executing the script then the
\fBbgerror\fR mechanism is used to report the error.
.TP
\fBafter info \fR?\fIid\fR?
This command returns information about existing event handlers.
If no \fIid\fR argument is supplied, the command returns
a list of the identifiers for all existing
event handlers created by the \fBafter\fR command for this
interpreter.
If \fIid\fR is supplied, it specifies an existing handler;
\fIid\fR must have been the return value from some previous call
to \fBafter\fR and it must not have triggered yet or been cancelled.
In this case the command returns a list with two elements.
The first element of the list is the script associated
with \fIid\fR, and the second element is either
\fBidle\fR or \fBtimer\fR to indicate what kind of event
handler it is.
.LP
The \fBafter \fIms\fR and \fBafter idle\fR forms of the command
assume that the application is event driven:  the delayed commands
will not be executed unless the application enters the event loop.
In applications that are not normally event-driven, such as
\fBtclsh\fR, the event loop can be entered with the \fBvwait\fR
and \fBupdate\fR commands.
.SH "EXAMPLES"
This defines a command to make Tcl do nothing at all for \fIN\fR
seconds:
.CS
proc sleep {N} {
   \fBafter\fR [expr {int($N * 1000)}]
}
.CE
.PP
This arranges for the command \fIwake_up\fR to be run in eight hours
(providing the event loop is active at that time):
.CS
\fBafter\fR [expr {1000 * 60 * 60 * 8}] wake_up
.CE
.PP
The following command can be used to do long-running calculations (as
represented here by \fI::my_calc::one_step\fR, which is assumed to
return a boolean indicating whether another step should be performed)
in a step-by-step fashion, though the calculation itself needs to be
arranged so it can work step-wise.  This technique is extra careful to
ensure that the event loop is not starved by the rescheduling of
processing steps (arranging for the next step to be done using an
already-triggered timer event only when the event queue has been
drained) and is useful when you want to ensure that a Tk GUI remains
responsive during a slow task.
.CS
proc doOneStep {} {
   if {[::my_calc::one_step]} {
      \fBafter idle\fR [list \fBafter\fR 0 doOneStep]
   }
}
doOneStep
.CE

.SH "SEE ALSO"
bgerror(n), concat(n), update(n), vwait(n)

.SH KEYWORDS
cancel, delay, idle callback, sleep, time