event -
Miscellaneous event facilities: define virtual events and generate events
event option ?arg arg ...?
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.
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:
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.
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.
- <<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.
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 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.
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.
bind(n)
event, binding, define, handle, virtual event