Provided by: tk8.5-doc_8.5.15-2ubuntu3_all 
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 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:
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.
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 a text widget when the ttk (Tile) theme 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(3tk)
KEYWORDS
event, binding, define, handle, virtual event