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event(n)		     Tk Built-In Commands		      event(n)

______________________________________________________________________________

NAME
       event  - Miscellaneous event facilities: define virtual events and gen‐
       erate 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	 argu‐
       ment.  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 asso‐
	      ciated  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-But‐
	      ton-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  pat‐
	      tern, 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  han‐
	      dlers for the event will complete before the event generate com‐
	      mand returns.  If the -when option is specified then  it	deter‐
	      mines  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  vir‐
	      tual events that are currently defined.  If <<virtual>> is spec‐
	      ified 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 win‐
	      dow  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  num‐
	      ber 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  substi‐
	      tution 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	magni‐
	      tude  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	 NotifyDetail‐
	      None	  NotifyPointer NotifyInferior		NotifyPointer‐
	      Root  NotifyNonlinear	    NotifyVirtual  Valid  for	Enter,
	      Leave,  FocusIn and FocusOut events.  Corresponds to the %d sub‐
	      stitution 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.	Corre‐
	      sponds 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.  Cor‐
	      responds 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.	Corre‐
	      sponds to the %m substitution for binding scripts.

       -override boolean
	      Boolean  must be a boolean value;	 it specifies the override_re‐
	      direct field for the event.  Valid for Map, Reparent,  and  Con‐
	      figure  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 %# substi‐
	      tution 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,	VisibilityPartiallyOb‐
	      scured, 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.	  Cor‐
	      responds 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, Button‐
	      Release, 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, Button‐
	      Release, 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  notifica‐
       tion:

       <<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  hap‐
       pen.   First, the virtual event must be defined with the event add com‐
       mand.  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 mean‐
       ingless 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 pre‐
       ceding 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

Tk				      8.3			      event(n)
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