1after(3) User Contributed Perl Documentation after(3)
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6 Tk::after - Execute a command after a time delay
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9 $widget->after(ms)
10 $id = $widget->after(ms?,callback?)
12 $id = $widget->repeat(ms?,callback?)
14 $widget->afterCancel($id)
16 $id = $widget->afterIdle(callback)
18 $widget->afterInfo?($id)?
20 $id->time(?delay?)
22
24 This method is used to delay execution of the program or to execute a
25 callback in background sometime in the future.
26 In perl/Tk $widget->after is implemented via the class "Tk::After", and
28 callbacks are associated with $widget, and are automatically cancelled
29 when the widget is destroyed. An almost identical interface, but with‐
30 out automatic cancel, and without repeat is provided via Tk::after
31 method.
32 Internal Details
34 The internal Tk::After class has the following synopsis:
36 $id = Tk::After->new($widget, tid, $time, 'once', callback);
38 $id = Tk::After->new($widget, tid, $time, 'repeat', callback);
39 $id->cancel;
40 $id->time(?delay?);
41 $id is a Tk::After object, an array of 5 elements:
43 $widget is the parent widget reference.
45 tid is the internal timer id, a unique string.
47 $time is the string 'idle', representing an idle queue timer, or a
49 integer millisecond value.
50 once or repeat specifies whether the timer is a one-time after event,
52 or a repeating repeat event.
53 callback specifies a Perl/Tk Tk::Callback object.
55
57 It's posible to change a repeat timer's delay value, or even cancel any
58 timer, using the time method. If delay is specified and non-zero, a new
59 timer delay is established. If delay is zero the timer event is can‐
60 celed just as if $id->cancel were invoked. In all cases the current
61 millisecond timer delay is returned.
62 Note: the new timer delay will take effect on the subsequent timer
64 event - this command will not cancel the pending timer event and re-
65 issue it with the new delay time.
66
68 $widget->after(ms)
69 The value ms must be an integer giving a time in milliseconds. The
70 command sleeps for ms milliseconds and then returns. While the
71 command is sleeping the application does not respond to events.
72 $widget->after(ms,callback)
74 In this form the command returns immediately, but it arranges for
75 callback be executed ms milliseconds later as an event handler.
76 The callback will be executed exactly once, at the given time. The
77 command will be executed in context of $widget. If an error occurs
78 while executing the delayed command then the Tk::Error mechanism is
79 used to report the error. The after command returns an identifier
80 (an object in the perl/Tk case) that can be used to cancel the
81 delayed command using afterCancel.
82 $widget->repeat(ms,callback)
84 In this form the command returns immediately, but it arranges for
85 callback be executed ms milliseconds later as an event handler.
86 After callback has executed it is re-scheduled, to be executed in a
87 futher ms, and so on until it is cancelled.
88 $widget->afterCancel($id)
90 $id->cancel
91 Cancels the execution of a delayed command that was previously
92 scheduled. $id indicates which command should be canceled; it
93 must have been the return value from a previous after command. If
94 the command given by $id has already been executed (and is not
95 scheduled to be executed again) then afterCancel has no effect.
96 $widget->afterCancel(callback)
98 This form is not robust in perl/Tk - its use is deprecated. This
99 command should also cancel the execution of a delayed command. The
100 callback argument is compared with pending callbacks, if a match is
101 found, that callback is cancelled and will never be executed; if
102 no such callback is currently pending then the afterCancel has no
103 effect.
104 $widget->afterIdle(callback)
106 Arranges for callback to be evaluated later as an idle callback.
107 The script will be run exactly once, the next time the event loop
108 is entered and there are no events to process. The command returns
109 an identifier that can be used to cancel the delayed command using
110 afterCancel. If an error occurs while executing the script then
111 the Tk::Error mechanism is used to report the error.
112 $widget->afterInfo?($id)?
114 This command returns information about existing event handlers. If
115 no $id argument is supplied, the command returns a list of the
116 identifiers for all existing event handlers created by the after
117 and repeat commands for $widget. If $id is supplied, it specifies
118 an existing handler; $id must have been the return value from some
119 previous call to after or repeat and it must not have triggered yet
120 or been cancelled. In this case the command returns a list with
121 three elements. The first element of the list is the callback
122 associated with $id, the second element is either idle or the inte‐
123 ger timer millisecond value to indicate what kind of event handler
124 it is, and the third is a string once or repeat to differentiate an
125 after from a repeat event.
126 The after(ms) and afterIdle forms of the command assume that the appli‐
128 cation is event driven: the delayed commands will not be executed
129 unless the application enters the event loop. In applications that are
130 not normally event-driven, the event loop can be entered with the vwait
131 and update commands.
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134 Tk::Error Tk::callbacks
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137 cancel, delay, idle callback, sleep, time
138perl v5.8.8 2008-02-05 after(3)