NAME
event - Miscellaneous event facilities: define virtual
events and generate events
SYNOPSIS
event option ?arg arg ...?
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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 differ
ent forms, determined by the first argument. The follow
ing forms are currently supported:
event add <<virtual>> sequence ?sequence ...?
Associates the virtual event virtual with the phys
ical event sequence(s) given by the sequence argu
ments, so that the virtual event will trigger when
ever 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 vir
tual 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 applica |
tion. 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
Option-value pairs may be used to specify addi
tional 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 pro
cessed immediately: all of the handlers for the
event will complete before the event generate com
mand 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 cur
rently 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.
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 win
dow 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 Con
figure 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.
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. Typi
cally these values are multiples of 120. For exam
ple, 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 cor
responds 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 key
code field for the event. Valid for KeyPress and
KeyRelease events. Corresponds to the %k substitu
tion 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. Corre
sponds to the %K substitution for binding scripts.
Notify specifies the mode field for the event and
must be one of NotifyNormal, NotifyGrab, NotifyUn
grab, 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 sub
stitution 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, KeyRe
lease, ButtonPress, ButtonRelease, Enter, Leave,
and Motion events. Corresponds to the %R substitu
tion 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 th
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. Corre
sponds to the %# substitution for binding scripts.
-state state
State specifies the state field for the event. For
Enter, Leave, and Motion events it must be an inte
ger 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 substitu
tion 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
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, KeyRe
lease, ButtonPress, ButtonRelease, Motion, Enter,
Leave, Expose, Configure, Gravity, and Reparent
events. Corresponds to the the %x substitution for
binding scripts. If Window is empty the coordinate
is relative to the screen, and this option corre
sponds 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, KeyRe
lease, ButtonPress, ButtonRelease, Motion, Enter,
Leave, Expose, Configure, Gravity, and Reparent
events. Corresponds to the the %y substitution for
binding scripts. If Window is empty the coordinate
is relative to the screen, and this option corre
sponds 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
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 com
mand. 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 vir
tual event is being bound. If the user types Control-y or
presses button 2, or if a <<Paste>> virtual event is syn
thesized with event generate, then the <<Paste>> binding
will be invoked.
If a virtual binding has the exact same sequence as a sep
arate physical binding, then the physical binding will
take precedence. Consider the following example:
event add <<Paste>> <Control-y> <Meta-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 modi
fier 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 vir
tual event exists. Indeed, the virtual event never actu
ally needs to be defined, for instance, on platforms where
the specific virtual event would meaningless or ungenerat
able.
When a definition of a virtual event changes at run time,
all windows will respond immediately to the new defini
tion. Starting from the preceding example, if the follow
ing 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
KEYWORDS
event, binding, define, handle, virtual event
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