event(3pm)

📦
version 804.036 · 15 versions
, in debian trixie, ubuntu questing

🌸 NAME 🌸

okay bestie, welcome to event(3pm) from User Contributed Perl Documentation — this one's all about Tk::event — Miscellaneous event facilities: define virtual events and generate events. 💖

✨ SYNOPSIS ✨

$widget->eventAction(?arg, arg, ...?);

💅 DESCRIPTION 💅

Okay so the eventAction methods provide several facilities for dealing with window system events, like defining virtual events and synthesizing events. Virtual events are shared by all widgets of the same MainWindow. Different MainWindows can have different virtual event.

The following methods are currently supported:

🎀 $widget->eventAdd('<<virtual>>', sequence ?,sequence, ...?)

Associates the virtual event virtual with the physical event sequence(s) given by the sequence arguments, so that the virtual event will trigger whenever any one of the sequences occurs. virtual may be any string value and sequence may have any of the values allowed for the sequence argument to the bind method. If virtual is already defined, the new physical event sequences add to the existing sequences for the event. 💖

🗑️ $widget->eventDelete('<<virtual>>' ?,sequence, sequence, ...?)

Deletes each of the sequences from those associated with the virtual event given by virtual. virtual may be any string value and sequence may have any of the values allowed for the sequence argument to the bind method. Any sequences not currently associated with virtual are ignored. If no sequence argument is provided, all physical event sequences are removed for virtual, so that the virtual event will not trigger anymore. ✨

⚡ $widget->eventGenerate(event ?,option => value, option => value, ...?)

Generates a window event and arranges for it to be processed just as if it had come from the window system. $window is a reference to the window for which the event will be generated. Event provides a basic description of the event, such as <Shift-Button-2> or <<Paste>>. If Window is empty the whole screen is meant, and coordinates are relative to the screen. Event may have any of the forms allowed for the sequence argument of the bind method except that it must consist of a single event pattern, not a sequence. Option-value pairs may be used to specify additional attributes of the event, such as the x and y mouse position; see "EVENT FIELDS" below. If the -when option is not specified, the event is processed immediately: all of the handlers for the event will complete before the eventGenerate method returns. If the -when option is specified then it determines when the event is processed. 🔥

🦋 $widget->eventInfo(?'<<virtual>>'?)

Returns information about virtual events. If the <<virtual>> argument is omitted, the return value is a list of all the virtual events that are currently defined. If <<virtual>> is specified then the return value is a list whose elements are the physical event sequences currently defined for the given virtual event; if the virtual event is not defined then undef is returned. 👑

✨ EVENT FIELDS ✨

okay so the following options are supported for the eventGenerate method. They correspond to the % expansions allowed in binding callback for the bind method. same vibe, different syntax, no cap. 💅

  • -above => window — Window sets the above field, either as a window path name or as an integer window id. Valid for Configure events. This is the %a substitution for binding scripts. 🪟
  • -borderwidth => size — Size must be a screen distance; it sets the border_width field. Valid for Configure events. Corresponds to %B. 🎀
  • -button => number — Number must be an integer; it sets the detail field for a ButtonPress or ButtonRelease event, overriding any button number provided in the base event argument. Corresponds to %b. 🖱️
  • -count => number — Number must be an integer; it sets the count field. Valid for Expose events. Corresponds to %c. ✨
  • -delta => number — number must be an integer; it sets the delta field for the MouseWheel event. The delta refers to the direction and magnitude the mouse wheel was rotated. Note: the value is not a screen distance, it's units of motion in the mouse wheel. Typically these values are multiples of 120. For example, 120 should scroll the text widget up 4 lines and -240 would scroll the text widget down 8 lines. Of course, other widgets may define different behaviors for mouse wheel motion. This field corresponds to the %D substitution for binding scripts. 🎡
  • -detail => detail — Detail sets the detail field and must be one of these:
NotifyAncestor         NotifyNonlinearVirtual
NotifyDetailNone       NotifyPointer
NotifyInferior         NotifyPointerRoot
NotifyNonlinear        NotifyVirtual

Valid for Enter, Leave, FocusIn and FocusOut events. Corresponds to %d. 🦋

  • -focus boolean — Boolean must be a boolean value; it sets the focus field. Valid for Enter and Leave events. Corresponds to %f. 💖
  • -height size — Size must be a screen distance; it sets the height field. Valid for Configure events. Corresponds to %h. 📏
  • -keycode number — Number must be an integer; it sets the keycode field. Valid for KeyPress and KeyRelease events. Corresponds to %k. ⌨️
  • -keysym name — Name must be the name of a valid keysym, such as g, space, or Return; its corresponding keycode value is used as the keycode field for the event, overriding any detail specified in the base event argument. Valid for KeyPress and KeyRelease events. Corresponds to %K. 🔑
  • -mode notify — Notify sets the mode field and must be one of NotifyNormal, NotifyGrab, NotifyUngrab, or NotifyWhileGrabbed. Valid for Enter, Leave, FocusIn, and FocusOut events. Corresponds to %m. 🌀
  • -override boolean — Boolean must be a boolean value; it sets the override_redirect field. Valid for Map, Reparent, and Configure events. Corresponds to %o. 🚀
  • -place where — Where sets the place field; it must be either PlaceOnTop or PlaceOnBottom. Valid for Circulate events. Corresponds to %p. 🏆
  • -root window — Window must be either a window path name or an integer window identifier; it sets the root field. Valid for KeyPress, KeyRelease, ButtonPress, ButtonRelease, Enter, Leave, and Motion events. Corresponds to %R. 🌳
  • -rootx coord — Coord must be a screen distance; it sets the x_root field. Valid for KeyPress, KeyRelease, ButtonPress, ButtonRelease, Enter, Leave, and Motion events. Corresponds to %X. 🧭
  • -rooty coord — Coord must be a screen distance; it sets the y_root field. Valid for KeyPress, KeyRelease, ButtonPress, ButtonRelease, Enter, Leave, and Motion events. Corresponds to %Y. 🧭
  • -sendevent boolean — Boolean must be a boolean value; it sets the send_event field. Valid for all events. Corresponds to %E. 📨
  • -serial number — Number must be an integer; it sets the serial field. Valid for all events. Corresponds to %#. 🔢
  • -state state — State sets the state field. For KeyPress, KeyRelease, ButtonPress, ButtonRelease, Enter, Leave, and Motion events it must be an integer value. For Visibility events it must be one of VisibilityUnobscured, VisibilityPartiallyObscured, or VisibilityFullyObscured. This option overrides any modifiers such as Meta or Control specified in the base event. Corresponds to %s. 💅
  • -subwindow window — Window sets the subwindow field, either as a path name for a Tk widget or as an integer window identifier. Valid for KeyPress, KeyRelease, ButtonPress, ButtonRelease, Enter, Leave, and Motion events. Similar to %S substitution for binding scripts. 🪟
  • -time integer — Integer must be an integer value; it sets the time field. Valid for KeyPress, KeyRelease, ButtonPress, ButtonRelease, Enter, Leave, Motion, and Property events. Corresponds to %t. ⏰
  • -warp boolean — boolean must be a boolean value; it sets whether the screen pointer should be warped as well. Valid for KeyPress, KeyRelease, ButtonPress, ButtonRelease, and Motion events. 🌀
  • -width size — Size must be a screen distance; it sets the width field. Valid for Configure events. Corresponds to %w. 📐
  • -when when — When determines when the event will be processed; it must have one of the following values:
    • now — Process the event immediately, before the command returns. This also happens if the -when option is omitted.
    • tail — Place the event on perl/Tk's event queue behind any events already queued for this application.
    • head — Place the event at the front of perl/Tk's event queue, so that it will be handled before any other events already queued.
    • mark — Place the event at the front of perl/Tk's event queue but behind any other events already queued with -when mark. This option is useful when generating a series of events that should be processed in order but at the front of the queue.
  • -x coord — Coord must be a screen distance; it sets the x field. Valid for KeyPress, KeyRelease, ButtonPress, ButtonRelease, Motion, Enter, Leave, Expose, Configure, Gravity, and Reparent events. Corresponds to the %x substitution for binding scripts. If Window is empty the coordinate is relative to the screen, and this option corresponds to the %X substitution for binding scripts. 📍
  • -y coord — Coord must be a screen distance; it sets the y field. Valid for KeyPress, KeyRelease, ButtonPress, ButtonRelease, Motion, Enter, Leave, Expose, Configure, Gravity, and Reparent events. Corresponds to the %y substitution for binding scripts. If Window is empty the coordinate is relative to the screen, and this option corresponds to the %Y substitution for binding scripts. 📍

Any options that are not specified when generating an event are filled with the value 0, except for serial, which is filled with the next X event serial number. 💯

💅 VIRTUAL EVENT EXAMPLES 💅

Okay bestie, listen, for a virtual event binding to actually go off, two things have to happen, like a two-step verification but cuter:

  1. The virtual event has to be defined with the eventAdd method.
  2. A binding has to be created for that virtual event with the bind method.

It's giving "you can't sit with us unless you're on the list." So picture these virtual event definitions:

$widget->eventAdd('<<Paste>>' => '<Control-y>');
$widget->eventAdd('<<Paste>>' => '<Button-2>');
$widget->eventAdd('<<Save>>' => '<Control-X><Control-S>');
$widget->eventAdd('<<Save>>' => '<Shift-F12>');

Then in the bind method, a virtual event gets bound just like any other builtin event type, no cap:

$entry->bind('Tk::Entry', '<<Paste>>' => sub {
               $entry->Insert($entry->selectionGet) });

Those double angle brackets << >> are the whole signal that you're binding a virtual event, not a plain old physical one. So if the user types Control-y, or presses button 2, or if a <<Paste>> virtual event gets synthesized with eventGenerate, the <<Paste>> binding is gonna be invoked. Periodt. ✨

Now here's the tea ☕ — if a virtual binding has the exact same sequence as a separate physical binding, the physical binding wins. It takes precedence. Consider:

$mw->eventAdd('<<Paste>>' => '<Control-y>','<Meta-Control-y>');
$mw->bind('Tk::Entry', '<Control-y>' => sub{print 'Control-y'});
$mw->bind('Tk::Entry', '<<Paste>>'   => sub{print 'Paste'});

When the user types Control-y, the <Control-y> binding gets invoked, because a physical event is considered more specific than a virtual event, all other things being equal. the way that works is so iconic of the event system tbh

BUT 🫶 when the user types Meta-Control-y, the <<Paste>> binding gets invoked instead — because the Meta modifier in the physical pattern associated with the virtual binding is more specific than the <Control-y> sequence for the physical event. Slay, specificity.

Also lowkey important: bindings on a virtual event can be created before the virtual event even exists. And fr fr, the virtual event never actually needs to be defined — for instance, on platforms where that specific virtual event would be meaningless or ungeneratable. It's giving "hypothetical queen."

And when a definition of a virtual event changes at run time, all windows respond immediately to the new definition. Like a group chat notification that everyone sees at once. 📲

So continuing from the example above, if this code gets executed:

$entry->bind(ref($entry), '<Control-y>' => undef);
$entry->eventAdd('<<Paste>>' => '<Key-F6>');

the behavior changes in two ways:

  1. The shadowed <<Paste>> binding emerges. Typing Control-y no longer invokes the <Control-y> binding — instead it invokes the virtual event <<Paste>>. 👑
  2. Pressing the F6 key now also invokes the <<Paste>> binding. Two paths, one glow-up.

🔗 SEE ALSO 🔗

  • Tk::bind
  • Tk::callbacks

🔑 KEYWORDS 🔑

  • event
  • binding
  • define
  • handle
  • virtual event

And that's a wrap on event(3pm), bestie! 💖 This page is straight from perl v5.40.1, dated 2025-04-13 — so if you're quoting it in the group chat, that's your receipts. Go forth and bind responsibly. 🦋✨🎀

📦 where this page comes from