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1. event.3.man

Manpage of EVENT

EVENT

Section: C Library Functions (3)
Index Return to Main Contents

BSD mandoc
 

NAME

event_init event_dispatch event_loop event_loopexit event_loopbreak event_set event_base_dispatch event_base_loop event_base_loopexit event_base_loopbreak event_base_set event_base_free event_add event_del event_once event_base_once event_pending event_initialized event_priority_init event_priority_set evtimer_set evtimer_add evtimer_del evtimer_pending evtimer_initialized signal_set signal_add signal_del signal_pending signal_initialized bufferevent_new bufferevent_free bufferevent_write bufferevent_write_buffer bufferevent_read bufferevent_enable bufferevent_disable bufferevent_settimeout bufferevent_base_set evbuffer_new evbuffer_free evbuffer_add evbuffer_add_buffer evbuffer_add_printf evbuffer_add_vprintf evbuffer_drain evbuffer_write evbuffer_read evbuffer_find evbuffer_readline evhttp_new evhttp_bind_socket evhttp_free - execute a function when a specific event occurs  

SYNOPSIS

Fd #include <sys/time.h> Fd #include <event.h> Ft struct event_base * Fn event_init void Ft int Fn event_dispatch void Ft int Fn event_loop int flags Ft int Fn event_loopexit struct timeval *tv Ft int Fn event_loopbreak void Ft void Fn event_set struct event *ev int fd short event void (*fn)(int, short, void *) void *arg Ft int Fn event_base_dispatch struct event_base *base Ft int Fn event_base_loop struct event_base *base int flags Ft int Fn event_base_loopexit struct event_base *base struct timeval *tv Ft int Fn event_base_loopbreak struct event_base *base Ft int Fn event_base_set struct event_base *base struct event * Ft void Fn event_base_free struct event_base *base Ft int Fn event_add struct event *ev struct timeval *tv Ft int Fn event_del struct event *ev Ft int Fn event_once int fd short event void (*fn)(int, short, void *) void *arg struct timeval *tv Ft int Fn event_base_once struct event_base *base int fd short event void (*fn)(int, short, void *) void *arg struct timeval *tv Ft int Fn event_pending struct event *ev short event struct timeval *tv Ft int Fn event_initialized struct event *ev Ft int Fn event_priority_init int npriorities Ft int Fn event_priority_set struct event *ev int priority Ft void Fn evtimer_set struct event *ev void (*fn)(int, short, void *) void *arg Ft void Fn evtimer_add struct event *ev struct timeval * Ft void Fn evtimer_del struct event *ev Ft int Fn evtimer_pending struct event *ev struct timeval *tv Ft int Fn evtimer_initialized struct event *ev Ft void Fn signal_set struct event *ev int signal void (*fn)(int, short, void *) void *arg Ft void Fn signal_add struct event *ev struct timeval * Ft void Fn signal_del struct event *ev Ft int Fn signal_pending struct event *ev struct timeval *tv Ft int Fn signal_initialized struct event *ev Ft struct bufferevent * Fn bufferevent_new int fd evbuffercb readcb evbuffercb writecb everrorcb void *cbarg Ft void Fn bufferevent_free struct bufferevent *bufev Ft int Fn bufferevent_write struct bufferevent *bufev void *data size_t size Ft int Fn bufferevent_write_buffer struct bufferevent *bufev struct evbuffer *buf Ft size_t Fn bufferevent_read struct bufferevent *bufev void *data size_t size Ft int Fn bufferevent_enable struct bufferevent *bufev short event Ft int Fn bufferevent_disable struct bufferevent *bufev short event Ft void Fn bufferevent_settimeout struct bufferevent *bufev int timeout_read int timeout_write Ft int Fn bufferevent_base_set struct event_base *base struct bufferevent *bufev Ft struct evbuffer * Fn evbuffer_new void Ft void Fn evbuffer_free struct evbuffer *buf Ft int Fn evbuffer_add struct evbuffer *buf const void *data size_t size Ft int Fn evbuffer_add_buffer struct evbuffer *dst struct evbuffer *src Ft int Fn evbuffer_add_printf struct evbuffer *buf const char *fmt ... Ft int Fn evbuffer_add_vprintf struct evbuffer *buf const char *fmt va_list ap Ft void Fn evbuffer_drain struct evbuffer *buf size_t size Ft int Fn evbuffer_write struct evbuffer *buf int fd Ft int Fn evbuffer_read struct evbuffer *buf int fd int size Ft u_char * Fn evbuffer_find struct evbuffer *buf const u_char *data size_t size Ft char * Fn evbuffer_readline struct evbuffer *buf Ft struct evhttp * Fn evhttp_new struct event_base *base Ft int Fn evhttp_bind_socket struct evhttp *http const char *address u_short port Ft void Fn evhttp_free struct evhttp *http Ft int Fa (*event_sigcb)(void) ; Ft volatile sig_atomic_t Fa event_gotsig ;  

DESCRIPTION

The event API provides a mechanism to execute a function when a specific event on a file descriptor occurs or after a given time has passed.

The event API needs to be initialized with Fn event_init before it can be used.

In order to process events, an application needs to call Fn event_dispatch . This function only returns on error, and should replace the event core of the application program.

The function Fn event_set prepares the event structure Fa ev to be used in future calls to Fn event_add and Fn event_del . The event will be prepared to call the function specified by the Fa fn argument with an Fa int argument indicating the file descriptor, a Fa short argument indicating the type of event, and a Fa void * argument given in the Fa arg argument. The Fa fd indicates the file descriptor that should be monitored for events. The events can be either EV_READ EV_WRITE or both, indicating that an application can read or write from the file descriptor respectively without blocking.

The function Fa fn will be called with the file descriptor that triggered the event and the type of event which will be either EV_TIMEOUT EV_SIGNAL EV_READ or EV_WRITE Additionally, an event which has registered interest in more than one of the preceeding events, via bitwise-OR to Fn event_set , can provide its callback function with a bitwise-OR of more than one triggered event. The additional flag EV_PERSIST makes an Fn event_add persistent until Fn event_del has been called.

Once initialized, the Fa ev structure can be used repeatedly with Fn event_add and Fn event_del and does not need to be reinitialized unless the function called and/or the argument to it are to be changed. However, when an Fa ev structure has been added to libevent using Fn event_add the structure must persist until the event occurs (assuming Fa EV_PERSIST is not set) or is removed using Fn event_del . You may not reuse the same Fa ev structure for multiple monitored descriptors; each descriptor needs its own Fa ev .

The function Fn event_add schedules the execution of the Fa ev event when the event specified in Fn event_set occurs or in at least the time specified in the Fa tv . If Fa tv is NULL no timeout occurs and the function will only be called if a matching event occurs on the file descriptor. The event in the Fa ev argument must be already initialized by Fn event_set and may not be used in calls to Fn event_set until it has timed out or been removed with Fn event_del . If the event in the Fa ev argument already has a scheduled timeout, the old timeout will be replaced by the new one.

The function Fn event_del will cancel the event in the argument Fa ev . If the event has already executed or has never been added the call will have no effect.

The functions Fn evtimer_set , Fn evtimer_add , Fn evtimer_del , Fn evtimer_initialized , and Fn evtimer_pending are abbreviations for common situations where only a timeout is required. The file descriptor passed will be -1, and the event type will be EV_TIMEOUT

The functions Fn signal_set , Fn signal_add , Fn signal_del , Fn signal_initialized , and Fn signal_pending are abbreviations. The event type will be a persistent EV_SIGNAL That means Fn signal_set adds EV_PERSIST

In order to avoid races in signal handlers, the event API provides two variables: event_sigcb and event_gotsig A signal handler sets event_gotsig to indicate that a signal has been received. The application sets event_sigcb to a callback function. After the signal handler sets event_gotsig event_dispatch will execute the callback function to process received signals. The callback returns 1 when no events are registered any more. It can return -1 to indicate an error to the event library, causing Fn event_dispatch to terminate with errno set to Er EINTR .

The function Fn event_once is similar to Fn event_set . However, it schedules a callback to be called exactly once and does not require the caller to prepare an Fa event structure. This function supports Fa EV_TIMEOUT , Fa EV_READ , and Fa EV_WRITE .

The Fn event_pending function can be used to check if the event specified by Fa event is pending to run. If EV_TIMEOUT was specified and Fa tv is not NULL the expiration time of the event will be returned in Fa tv .

The Fn event_initialized macro can be used to check if an event has been initialized.

The event_loop function provides an interface for single pass execution of pending events. The flags EVLOOP_ONCE and EVLOOP_NONBLOCK are recognized. The event_loopexit function exits from the event loop. The next Fn event_loop iteration after the given timer expires will complete normally (handling all queued events) then exit without blocking for events again. Subsequent invocations of Fn event_loop will proceed normally. The event_loopbreak function exits from the event loop immediately. Fn event_loop will abort after the next event is completed; Fn event_loopbreak is typically invoked from this event's callback. This behavior is analogous to the "break;" statement. Subsequent invocations of Fn event_loop will proceed normally.

It is the responsibility of the caller to provide these functions with pre-allocated event structures.

 

EVENT PRIORITIES

By default libevent schedules all active events with the same priority. However, sometimes it is desirable to process some events with a higher priority than others. For that reason, libevent supports strict priority queues. Active events with a lower priority are always processed before events with a higher priority.

The number of different priorities can be set initially with the Fn event_priority_init function. This function should be called before the first call to Fn event_dispatch . The Fn event_priority_set function can be used to assign a priority to an event. By default, libevent assigns the middle priority to all events unless their priority is explicitly set.  

THREAD SAFE EVENTS

Libevent has experimental support for thread-safe events. When initializing the library via Fn event_init , an event base is returned. This event base can be used in conjunction with calls to Fn event_base_set , Fn event_base_dispatch , Fn event_base_loop , Fn event_base_loopexit , Fn bufferevent_base_set and Fn event_base_free . Fn event_base_set should be called after preparing an event with Fn event_set , as Fn event_set assigns the provided event to the most recently created event base. Fn bufferevent_base_set should be called after preparing a bufferevent with Fn bufferevent_new . Fn event_base_free should be used to free memory associated with the event base when it is no longer needed.  

BUFFERED EVENTS

libevent provides an abstraction on top of the regular event callbacks. This abstraction is called a buffered event A buffered event provides input and output buffers that get filled and drained automatically. The user of a buffered event no longer deals directly with the IO, but instead is reading from input and writing to output buffers.

A new bufferevent is created by Fn bufferevent_new . The parameter Fa fd specifies the file descriptor from which data is read and written to. This file descriptor is not allowed to be a pipe(2). The next three parameters are callbacks. The read and write callback have the following form: Ft void Fn (*cb) struct bufferevent *bufev void *arg . The error callback has the following form: Ft void Fn (*cb) struct bufferevent *bufev short what void *arg . The argument is specified by the fourth parameter Fa cbarg . A Fa bufferevent struct pointer is returned on success, NULL on error. Both the read and the write callback may be NULL. The error callback has to be always provided.

Once initialized, the bufferevent structure can be used repeatedly with bufferevent_enable() and bufferevent_disable(). The flags parameter can be a combination of EV_READ and EV_WRITE When read enabled the bufferevent will try to read from the file descriptor and call the read callback. The write callback is executed whenever the output buffer is drained below the write low watermark, which is 0 by default.

The Fn bufferevent_write function can be used to write data to the file descriptor. The data is appended to the output buffer and written to the descriptor automatically as it becomes available for writing. Fn bufferevent_write returns 0 on success or -1 on failure. The Fn bufferevent_read function is used to read data from the input buffer, returning the amount of data read.

If multiple bases are in use, bufferevent_base_set() must be called before enabling the bufferevent for the first time.  

NON-BLOCKING HTTP SUPPORT

libevent provides a very thin HTTP layer that can be used both to host an HTTP server and also to make HTTP requests. An HTTP server can be created by calling Fn evhttp_new . It can be bound to any port and address with the Fn evhttp_bind_socket function. When the HTTP server is no longer used, it can be freed via Fn evhttp_free .

To be notified of HTTP requests, a user needs to register callbacks with the HTTP server. This can be done by calling Fn evhttp_set_cb . The second argument is the URI for which a callback is being registered. The corresponding callback will receive an struct evhttp_request object that contains all information about the request.

This section does not document all the possible function calls; please check event.h for the public interfaces.  

ADDITIONAL NOTES

It is possible to disable support for epoll , kqueue , devpoll , poll or select by setting the environment variable EVENT_NOEPOLL , EVENT_NOKQUEUE , EVENT_NODEVPOLL , EVENT_NOPOLL or EVENT_NOSELECT respectively. By setting the environment variable EVENT_SHOW_METHOD libevent displays the kernel notification method that it uses.  

RETURN VALUES

Upon successful completion Fn event_add and Fn event_del return 0. Otherwise, -1 is returned and the global variable errno is set to indicate the error.  

SEE ALSO

kqueue(2), poll(2), select(2), evdns(3), timeout(9)  

HISTORY

The event API manpage is based on the timeout(9) manpage by Artur Grabowski. The port of libevent to Windows is due to Michael A. Davis. Support for real-time signals is due to Taral.  

AUTHORS

The event library was written by Niels Provos.  

BUGS

This documentation is neither complete nor authoritative. If you are in doubt about the usage of this API then check the source code to find out how it works, write up the missing piece of documentation and send it to me for inclusion in this man page.


 

Index

NAME
SYNOPSIS
DESCRIPTION
EVENT PRIORITIES
THREAD SAFE EVENTS
BUFFERED EVENTS
NON-BLOCKING HTTP SUPPORT
ADDITIONAL NOTES
RETURN VALUES
SEE ALSO
HISTORY
AUTHORS
BUGS

This document was created by man2html using the manual pages.
Time: 17:30:51 GMT, October 23, 2013

2. event.9.man

Manpage of event

event

Section: Tk Built-In Commands (n)
Updated: 8.3
Index Return to Main Contents



 

NAME

event - Miscellaneous event facilities: define virtual events and generate events  

SYNOPSIS

event option ?arg arg ...?



 

DESCRIPTION

The event command provides several facilities for dealing with window system events, such as defining virtual events and synthesizing events. The command has several different forms, determined by the first argument. The following forms are currently supported:

event add <<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 command. If virtual is already defined, the new physical event sequences add to the existing sequences for the event.
event delete <<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 command. 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.
event generate window 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 gives the path name of the window for which the event will be generated; it may also be an identifier (such as returned by winfo id) as long as it is for a window in the current application. 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 command 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 event generate command returns. If the -when option is specified then it determines when the event is processed. Certain events, such as key events, require that the window has focus to receive the event properly.
event info ?<<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 an empty string is returned.

Note that virtual events that that are not bound to physical event sequences are not returned by event info.

 

EVENT FIELDS

The following options are supported for the event generate command. These correspond to the ``%'' expansions allowed in binding scripts for the bind command.

-above window
Window specifies the above field for the event, either as a window path name or as an integer window id. Valid for Configure events. Corresponds to the %a substitution for binding scripts.
-borderwidth size
Size must be a screen distance; it specifies the border_width field for the event. Valid for Configure events. Corresponds to the %B substitution for binding scripts.
-button number
Number must be an integer; it specifies the detail field for a ButtonPress or ButtonRelease event, overriding any button number provided in the base event argument. Corresponds to the %b substitution for binding scripts.
-count number
Number must be an integer; it specifies the count field for the event. Valid for Expose events. Corresponds to the %c substitution for binding scripts.
-data string
String may be any value; it specifies the user_data field for the event. Only valid for virtual events. Corresponds to the %d substitution for virtual events in binding scripts.
-delta number
Number must be an integer; it specifies 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 but are 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 specifies the detail field for the event and must be one of the following:


NotifyAncestorNotifyNonlinearVirtual
NotifyDetailNoneNotifyPointer
NotifyInferiorNotifyPointerRoot
NotifyNonlinearNotifyVirtual

Valid for Enter, Leave, FocusIn and FocusOut events. Corresponds to the %d substitution for binding scripts.

-focus boolean
Boolean must be a boolean value; it specifies the focus field for the event. Valid for Enter and Leave events. Corresponds to the %f substitution for binding scripts.
-height size
Size must be a screen distance; it specifies the height field for the event. Valid for Configure events. Corresponds to the %h substitution for binding scripts.
-keycode number
Number must be an integer; it specifies the keycode field for the event. Valid for KeyPress and KeyRelease events. Corresponds to the %k substitution for binding scripts.
-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 event, overriding any detail specified in the base event argument. Valid for KeyPress and KeyRelease events. Corresponds to the %K substitution for binding scripts.
-mode notify
Notify specifies the mode field for the event and must be one of NotifyNormal, NotifyGrab, NotifyUngrab, or NotifyWhileGrabbed. Valid for Enter, Leave, FocusIn, and FocusOut events. Corresponds to the %m substitution for binding scripts.
-override boolean
Boolean must be a boolean value; it specifies the override_redirect field for the event. Valid for Map, Reparent, and Configure events. Corresponds to the %o substitution for binding scripts.
-place where
Where specifies the place field for the event; it must be either PlaceOnTop or PlaceOnBottom. Valid for Circulate events. Corresponds to the %p substitution for binding scripts.
-root window
Window must be either a window path name or an integer window identifier; it specifies the root field for the event. Valid for KeyPress, KeyRelease, ButtonPress, ButtonRelease, Enter, Leave, and Motion events. Corresponds to the %R substitution for binding scripts.
-rootx coord
Coord must be a screen distance; it specifies the x_root field for the event. Valid for KeyPress, KeyRelease, ButtonPress, ButtonRelease, Enter, Leave, and Motion events. Corresponds to the %X substitution for binding scripts.
-rooty coord
Coord must be a screen distance; it specifies the y_root field for the event. Valid for KeyPress, KeyRelease, ButtonPress, ButtonRelease, Enter, Leave, and Motion events. Corresponds to the %Y substitution for binding scripts.
-sendevent boolean
Boolean must be a boolean value; it specifies the send_event field for the event. Valid for all events. Corresponds to the %E substitution for binding scripts.
-serial number
Number must be an integer; it specifies the serial field for the event. Valid for all events. Corresponds to the %# substitution for binding scripts.
-state state
State specifies the state field for the event. 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 the %s substitution for binding scripts.
-subwindow window
Window specifies the subwindow field for the event, 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 specifies the time field for the event. Valid for KeyPress, KeyRelease, ButtonPress, ButtonRelease, Enter, Leave, Motion, and Property events. Corresponds to the %t substitution for binding scripts.
-warp boolean
boolean must be a boolean value; it specifies whether the screen pointer should be warped as well. Valid for KeyPress, KeyRelease, ButtonPress, ButtonRelease, and Motion events. The pointer will only warp to a window if it is mapped.
-width size
Size must be a screen distance; it specifies the width field for the event. Valid for Configure events. Corresponds to the %w substitution for binding scripts.
-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 Tcl's event queue behind any events already queued for this application.
head
Place the event at the front of Tcl's event queue, so that it will be handled before any other events already queued.
mark
Place the event at the front of Tcl'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 specifies the x field for the event. 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 specifies the y field for the event. 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.  

PREDEFINED VIRTUAL EVENTS

Tk defines the following virtual events for the purposes of notification:
<<AltUnderlined>>
This is sent to widget to notify it that the letter it has underlined (as an accelerator indicator) with the -underline option has been pressed in combination with the Alt key. The usual response to this is to either focus into the widget (or some related widget) or to invoke the widget.
<<ListboxSelect>>
This is sent to a listbox when the set of selected item(s) in the listbox is updated.
<<MenuSelect>>
This is sent to a menu when the currently selected item in the menu changes. It is intended for use with context-sensitive help systems.
<<Modified>>
This is sent to a text widget when the contents of the widget are changed.
<<Selection>>
This is sent to a text widget when the selection in the widget is changed.
<<TraverseIn>>
This is sent to a widget when the focus enters the widget because of a user-driven ``tab to widget'' action.
<<TraverseOut>>
This is sent to a widget when the focus leaves the widget because of a user-driven ``tab to widget'' action.

Tk defines the following virtual events for the purposes of unifying bindings across multiple platforms. Users expect them to behave in the following way:

<<Clear>>
Delete the currently selected widget contents.
<<Copy>>
Copy the currently selected widget contents to the clipboard.
<<Cut>>
Move the currently selected widget contents to the clipboard.
<<Paste>>
Replace the currently selected widget contents with the contents of the clipboard.
<<PasteSelection>>
Insert the contents of the selection at the mouse location. (This event has meaningful %x and %y substitutions).
<<PrevWindow>>
Traverse to the previous window.
<<Redo>>
Redo one undone action.
<<Undo>>
Undo the last action.
 

VIRTUAL EVENT EXAMPLES

In order for a virtual event binding to trigger, two things must happen. First, the virtual event must be defined with the event add command. Second, a binding must be created for the virtual event with the bind command. Consider the following virtual event definitions:


event add <<Paste>> <Control-y>
event add <<Paste>> <Button-2>
event add <<Save>> <Control-X><Control-S>
event add <<Save>> <Shift-F12>

In the bind command, a virtual event can be bound like any other builtin event type as follows:

bind Entry <<Paste>> {%W insert [selection get]}

The double angle brackets are used to specify that a virtual event is being bound. If the user types Control-y or presses button 2, or if a <<Paste>> virtual event is synthesized with event generate, then the <<Paste>> binding will be invoked.

If a virtual binding has the exact same sequence as a separate physical binding, then the physical binding will take precedence. Consider the following example:


event add <<Paste>> <Control-y> <Meta-Control-y>
bind Entry <Control-y> {puts Control-y}
bind Entry <<Paste>> {puts Paste}

When the user types Control-y the <Control-y> binding will be invoked, because a physical event is considered more specific than a virtual event, all other things being equal. However, when the user types Meta-Control-y the <<Paste>> binding will be invoked, 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.

Bindings on a virtual event may be created before the virtual event exists. Indeed, the virtual event never actually needs to be defined, for instance, on platforms where the specific virtual event would meaningless or ungeneratable.

When a definition of a virtual event changes at run time, all windows will respond immediately to the new definition. Starting from the preceding example, if the following code is executed:


bind <Entry> <Control-y> {}
event add <<Paste>> <Key-F6>

the behavior will change such in two ways. First, the shadowed <<Paste>> binding will emerge. Typing Control-y will no longer invoke the <Control-y> binding, but instead invoke the virtual event <<Paste>>. Second, pressing the F6 key will now also invoke the <<Paste>> binding.

 

SEE ALSO

bind(n)

 

KEYWORDS

event, binding, define, handle, virtual event


 

Index

NAME
SYNOPSIS
DESCRIPTION
EVENT FIELDS
PREDEFINED VIRTUAL EVENTS
VIRTUAL EVENT EXAMPLES
SEE ALSO
KEYWORDS

This document was created by man2html using the manual pages.
Time: 17:30:51 GMT, October 23, 2013

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