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event(n) Tk Built-In Commands event(n)
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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 gener-ated; generated;
ated; it may also be an identifier (such as returned by winfo id) as long as it is for a win-dow window
dow 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 spec-ified specified
ified then the return value is a list whose elements are the physical event sequences cur-rently currently
rently 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 vir- |
tual 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 multi-ples multiples
ples 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 Con-figure Configure
figure 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 key-code keycode
code 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 Key-Press, KeyPress,
Press, 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 Key-Press, KeyPress,
Press, 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, Button-Release, ButtonRelease,
Release, Enter, Leave, and Motion events it must be an integer value. For Visibility events
it must be one of VisibilityUnobscured, VisibilityPartiallyObscured, or VisibilityFullyOb-scured. VisibilityFullyObscured.
scured. 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 Key-Press, KeyPress,
Press, 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 Con-figure Configure
figure 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 indi-cator) indicator)
cator) 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 plat-forms. platforms.
forms. 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. Typ-ing Typing
ing 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
Tk 8.3 event(n)
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