DragonFly On-Line Manual Pages
EVENT(3) DragonFly Library Functions Manual EVENT(3)
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
#include <sys/time.h>
#include <event.h>
struct event_base *
event_init(void);
int
event_dispatch(void);
int
event_loop(int flags);
int
event_loopexit(struct timeval *tv);
int
event_loopbreak(void);
void
event_set(struct event *ev, int fd, short event,
void (*fn)(int, short, void *), void *arg);
int
event_base_dispatch(struct event_base *base);
int
event_base_loop(struct event_base *base, int flags);
int
event_base_loopexit(struct event_base *base, struct timeval *tv);
int
event_base_loopbreak(struct event_base *base);
int
event_base_set(struct event_base *base, struct event *);
void
event_base_free(struct event_base *base);
int
event_add(struct event *ev, struct timeval *tv);
int
event_del(struct event *ev);
int
event_once(int fd, short event, void (*fn)(int, short, void *),
void *arg, struct timeval *tv);
int
event_base_once(struct event_base *base, int fd, short event,
void (*fn)(int, short, void *), void *arg, struct timeval *tv);
int
event_pending(struct event *ev, short event, struct timeval *tv);
int
event_initialized(struct event *ev);
int
event_priority_init(int npriorities);
int
event_priority_set(struct event *ev, int priority);
void
evtimer_set(struct event *ev, void (*fn)(int, short, void *), void *arg);
void
evtimer_add(struct event *ev, struct timeval *);
void
evtimer_del(struct event *ev);
int
evtimer_pending(struct event *ev, struct timeval *tv);
int
evtimer_initialized(struct event *ev);
void
signal_set(struct event *ev, int signal, void (*fn)(int, short, void *),
void *arg);
void
signal_add(struct event *ev, struct timeval *);
void
signal_del(struct event *ev);
int
signal_pending(struct event *ev, struct timeval *tv);
int
signal_initialized(struct event *ev);
struct bufferevent *
bufferevent_new(int fd, evbuffercb readcb, evbuffercb writecb, everrorcb,
void *cbarg);
void
bufferevent_free(struct bufferevent *bufev);
int
bufferevent_write(struct bufferevent *bufev, void *data, size_t size);
int
bufferevent_write_buffer(struct bufferevent *bufev,
struct evbuffer *buf);
size_t
bufferevent_read(struct bufferevent *bufev, void *data, size_t size);
int
bufferevent_enable(struct bufferevent *bufev, short event);
int
bufferevent_disable(struct bufferevent *bufev, short event);
void
bufferevent_settimeout(struct bufferevent *bufev, int timeout_read,
int timeout_write);
int
bufferevent_base_set(struct event_base *base, struct bufferevent *bufev);
struct evbuffer *
evbuffer_new(void);
void
evbuffer_free(struct evbuffer *buf);
int
evbuffer_add(struct evbuffer *buf, const void *data, size_t size);
int
evbuffer_add_buffer(struct evbuffer *dst, struct evbuffer *src);
int
evbuffer_add_printf(struct evbuffer *buf, const char *fmt, ...);
int
evbuffer_add_vprintf(struct evbuffer *buf, const char *fmt, va_list ap);
void
evbuffer_drain(struct evbuffer *buf, size_t size);
int
evbuffer_write(struct evbuffer *buf, int fd);
int
evbuffer_read(struct evbuffer *buf, int fd, int size);
u_char *
evbuffer_find(struct evbuffer *buf, const u_char *data, size_t size);
char *
evbuffer_readline(struct evbuffer *buf);
struct evhttp *
evhttp_new(struct event_base *base);
int
evhttp_bind_socket(struct evhttp *http, const char *address,
u_short port);
void
evhttp_free(struct evhttp *http);
int (*event_sigcb)(void);
volatile sig_atomic_t 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 event_init() before it can be
used.
In order to process events, an application needs to call
event_dispatch(). This function only returns on error, and should
replace the event core of the application program.
The function event_set() prepares the event structure ev to be used in
future calls to event_add() and event_del(). The event will be prepared
to call the function specified by the fn argument with an int argument
indicating the file descriptor, a short argument indicating the type of
event, and a void * argument given in the arg argument. The 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 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 regis-
tered interest in more than one of the preceeding events, via bitwise-OR
to event_set(), can provide its callback function with a bitwise-OR of
more than one triggered event. The additional flag EV_PERSIST makes an
event_add() persistent until event_del() has been called.
Once initialized, the ev structure can be used repeatedly with
event_add() and event_del() and does not need to be reinitialized unless
the function called and/or the argument to it are to be changed. How-
ever, when an ev structure has been added to libevent using event_add()
the structure must persist until the event occurs (assuming EV_PERSIST is
not set) or is removed using event_del(). You may not reuse the same ev
structure for multiple monitored descriptors; each descriptor needs its
own ev.
The function event_add() schedules the execution of the ev event when the
event specified in event_set() occurs or in at least the time specified
in the tv. If 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 ev argument must be already initialized by event_set() and may not
be used in calls to event_set() until it has timed out or been removed
with event_del(). If the event in the ev argument already has a sched-
uled timeout, the old timeout will be replaced by the new one.
The function event_del() will cancel the event in the argument ev. If
the event has already executed or has never been added the call will have
no effect.
The functions evtimer_set(), evtimer_add(), evtimer_del(),
evtimer_initialized(), and 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 signal_set(), signal_add(), signal_del(),
signal_initialized(), and signal_pending() are abbreviations. The event
type will be a persistent EV_SIGNAL. That means 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 applica-
tion 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 reg-
istered any more. It can return -1 to indicate an error to the event
library, causing event_dispatch() to terminate with errno set to EINTR.
The function event_once() is similar to event_set(). However, it sched-
ules a callback to be called exactly once and does not require the caller
to prepare an event structure. This function supports EV_TIMEOUT,
EV_READ, and EV_WRITE.
The event_pending() function can be used to check if the event specified
by event is pending to run. If EV_TIMEOUT was specified and tv is not
NULL, the expiration time of the event will be returned in tv.
The 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 recog-
nized. The event_loopexit function exits from the event loop. The next
event_loop() iteration after the given timer expires will complete nor-
mally (handling all queued events) then exit without blocking for events
again. Subsequent invocations of event_loop() will proceed normally. The
event_loopbreak function exits from the event loop immediately.
event_loop() will abort after the next event is completed;
event_loopbreak() is typically invoked from this event's callback. This
behavior is analogous to the "break;" statement. Subsequent invocations
of 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
event_priority_init() function. This function should be called before
the first call to event_dispatch(). The 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 initial-
izing the library via event_init(), an event base is returned. This
event base can be used in conjunction with calls to event_base_set(),
event_base_dispatch(), event_base_loop(), event_base_loopexit(),
bufferevent_base_set() and event_base_free(). event_base_set() should be
called after preparing an event with event_set(), as event_set() assigns
the provided event to the most recently created event base.
bufferevent_base_set() should be called after preparing a bufferevent
with bufferevent_new(). 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 bufferevent_new(). The parameter 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: void (*cb)(struct bufferevent *bufev, void *arg). The error call-
back has the following form: void (*cb)(struct bufferevent *bufev, short
what, void *arg). The argument is specified by the fourth parameter
cbarg. A 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 buffer-
event will try to read from the file descriptor and call the read call-
back. The write callback is executed whenever the output buffer is
drained below the write low watermark, which is 0 by default.
The 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.
bufferevent_write() returns 0 on success or -1 on failure. The
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 cre-
ated by calling evhttp_new(). It can be bound to any port and address
with the evhttp_bind_socket() function. When the HTTP server is no
longer used, it can be freed via evhttp_free().
To be notified of HTTP requests, a user needs to register callbacks with
the HTTP server. This can be done by calling evhttp_set_cb(). The sec-
ond 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 set-
ting the environment variable EVENT_SHOW_METHOD, libevent displays the
kernel notification method that it uses.
RETURN VALUES
Upon successful completion event_add() and event_del() return 0. Other-
wise, -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.
DragonFly 4.1 August 8, 2000 DragonFly 4.1
event(n) Tk Built-In Commands event(n)
______________________________________________________________________________
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 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:
NotifyAncestor NotifyNonlinearVirtual
NotifyDetailNone NotifyPointer
NotifyInferior NotifyPointerRoot
NotifyNonlinear NotifyVirtual
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. Additonally the special value current is allowed,
this value will be substituted by the current event time. 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.
<<Invoke>>
This can be sent to some widgets (e.g. button, listbox, menu) as
an alternative to <space>.
<<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.
<<ThemeChanged>>
This is sent to all widgets when the ttk theme changed. The ttk
widgets listen to this event and redisplay themselves when it
fires. The legacy widgets ignore this event.
<<TkWorldChanged>>
This event is sent to all widgets when a font is changed, for
example, by the use of [font configure]. The user_data field
(%d) will have the value "FontChanged". For other system wide
changes, this event will be sent to all widgets, and the
user_data field will indicate the cause of the change. NOTE:
all tk and ttk widgets already handle this event internally.
<<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.
<<UndoStack>>
This is sent to a text widget when its undo stack or redo stack
becomes empty or unempty.
<<WidgetViewSync>>
This is sent to a text widget when its internal data become
obsolete, and again when these internal data are back in sync
with the widget view. The detail field (%d substitution) is
either true (when the widget is in sync) or false (when it is
not).
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.
<<LineEnd>>
Move to the end of the line in the current widget while
deselecting any selected contents.
<<LineStart>>
Move to the start of the line in the current widget while
deselecting any selected contents.
<<NextChar>>
Move to the next item (i.e., visible character) in the current
widget while deselecting any selected contents.
<<NextLine>>
Move to the next line in the current widget while deselecting
any selected contents.
<<NextPara>>
Move to the next paragraph in the current widget while
deselecting any selected contents.
<<NextWord>>
Move to the next group of items (i.e., visible word) in the
current widget while deselecting any selected contents.
<<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).
<<PrevChar>>
Move to the previous item (i.e., visible character) in the
current widget while deselecting any selected contents.
<<PrevLine>>
Move to the previous line in the current widget while
deselecting any selected contents.
<<PrevPara>>
Move to the previous paragraph in the current widget while
deselecting any selected contents.
<<PrevWindow>>
Traverse to the previous window.
<<PrevWord>>
Move to the previous group of items (i.e., visible word) in the
current widget while deselecting any selected contents.
<<Redo>>
Redo one undone action.
<<SelectAll>>
Set the range of selected contents to the complete widget.
<<SelectLineEnd>>
Move to the end of the line in the current widget while
extending the range of selected contents.
<<SelectLineStart>>
Move to the start of the line in the current widget while
extending the range of selected contents.
<<SelectNextChar>>
Move to the next item (i.e., visible character) in the current
widget while extending the range of selected contents.
<<SelectNextLine>>
Move to the next line in the current widget while extending the
range of selected contents.
<<SelectNextPara>>
Move to the next paragraph in the current widget while extending
the range of selected contents.
<<SelectNextWord>>
Move to the next group of items (i.e., visible word) in the
current widget while extending the range of selected contents.
<<SelectNone>>
Reset the range of selected contents to be empty.
<<SelectPrevChar>>
Move to the previous item (i.e., visible character) in the
current widget while extending the range of selected contents.
<<SelectPrevLine>>
Move to the previous line in the current widget while extending
the range of selected contents.
<<SelectPrevPara>>
Move to the previous paragraph in the current widget while
extending the range of selected contents.
<<SelectPrevWord>>
Move to the previous group of items (i.e., visible word) in the
current widget while extending the range of selected contents.
<<ToggleSelection>>
Toggle the selection.
<<Undo>>
Undo the last action.
EXAMPLES
MAPPING KEYS TO VIRTUAL EVENTS
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>
if {[tk windowingsystem] eq "aqua"} {
event add <<Save>> <Command-s>
}
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 be
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.
MOVING THE MOUSE POINTER
Sometimes it is useful to be able to really move the mouse pointer. For
example, if you have some software that is capable of demonstrating
directly to the user how to use the program. To do this, you need to
"warp" the mouse around by using event generate, like this:
for {set xy 0} {$xy < 200} {incr xy} {
event generate . <Motion> -x $xy -y $xy -warp 1
update
after 50
}
Note that it is usually considered bad style to move the mouse pointer
for the user because it removes control from them. Therefore this
technique should be used with caution. Also note that it is not
guaranteed to function on all platforms.
SEE ALSO
bind(n)
KEYWORDS
event, binding, define, handle, virtual event
Tk 8.3 event(n)