1after(3) User Contributed Perl Documentation after(3)
2
6 Tk::after - Execute a command after a time delay
7
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
30 without 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:
35 $id = Tk::After->new($widget, tid, $time, 'once', callback);
37 $id = Tk::After->new($widget, tid, $time, 'repeat', callback);
38 $id->cancel;
39 $id->time(?delay?);
40 $id is a Tk::After object, an array of 5 elements:
42 $widget is the parent widget reference.
44 tid is the internal timer id, a unique string.
46 $time is the string 'idle', representing an idle queue timer, or a
48 integer millisecond value.
49 once or repeat specifies whether the timer is a one-time after event,
51 or a repeating repeat event.
52 callback specifies a Perl/Tk Tk::Callback object.
54
56 It's posible to change a repeat timer's delay value, or even cancel any
57 timer, using the time method. If delay is specified and non-zero, a new
58 timer delay is established. If delay is zero the timer event is
59 canceled just as if $id->cancel were invoked. In all cases the current
60 millisecond timer delay is returned.
61 Note: the new timer delay will take effect on the subsequent timer
63 event - this command will not cancel the pending timer event and re-
64 issue it with the new delay time.
65
67 $widget->after(ms)
68 The value ms must be an integer giving a time in milliseconds. The
69 command sleeps for ms milliseconds and then returns. While the
70 command is sleeping the application does not respond to events.
71 $widget->after(ms,callback)
73 In this form the command returns immediately, but it arranges for
74 callback be executed ms milliseconds later as an event handler.
75 The callback will be executed exactly once, at the given time. The
76 command will be executed in context of $widget. If an error occurs
77 while executing the delayed command then the Tk::Error mechanism is
78 used to report the error. The after command returns an identifier
79 (an object in the perl/Tk case) that can be used to cancel the
80 delayed command using afterCancel.
81 $widget->repeat(ms,callback)
83 In this form the command returns immediately, but it arranges for
84 callback be executed ms milliseconds later as an event handler.
85 After callback has executed it is re-scheduled, to be executed in a
86 futher ms, and so on until it is cancelled.
87 $widget->afterCancel($id)
89 $id->cancel
90 Cancels the execution of a delayed command that was previously
91 scheduled. $id indicates which command should be canceled; it
92 must have been the return value from a previous after command. If
93 the command given by $id has already been executed (and is not
94 scheduled to be executed again) then afterCancel has no effect.
95 $widget->afterCancel(callback)
97 This form is not robust in perl/Tk - its use is deprecated. This
98 command should also cancel the execution of a delayed command. The
99 callback argument is compared with pending callbacks, if a match is
100 found, that callback is cancelled and will never be executed; if
101 no such callback is currently pending then the afterCancel has no
102 effect.
103 $widget->afterIdle(callback)
105 Arranges for callback to be evaluated later as an idle callback.
106 The script will be run exactly once, the next time the event loop
107 is entered and there are no events to process. The command returns
108 an identifier that can be used to cancel the delayed command using
109 afterCancel. If an error occurs while executing the script then
110 the Tk::Error mechanism is used to report the error.
111 $widget->afterInfo?($id)?
113 This command returns information about existing event handlers. If
114 no $id argument is supplied, the command returns a list of the
115 identifiers for all existing event handlers created by the after
116 and repeat commands for $widget. If $id is supplied, it specifies
117 an existing handler; $id must have been the return value from some
118 previous call to after or repeat and it must not have triggered yet
119 or been cancelled. In this case the command returns a list with
120 three elements. The first element of the list is the callback
121 associated with $id, the second element is either idle or the
122 integer timer millisecond value to indicate what kind of event
123 handler it is, and the third is a string once or repeat to
124 differentiate an after from a repeat event.
125 The after(ms) and afterIdle forms of the command assume that the
127 application is event driven: the delayed commands will not be executed
128 unless the application enters the event loop. In applications that are
129 not normally event-driven, the event loop can be entered with the vwait
130 and update commands.
131
133 Tk::Error Tk::callbacks
134
136 cancel, delay, idle callback, sleep, time
137perl v5.32.1 2021-01-27 after(3)