Provided by: tk8.6-doc_8.6.10-1_all bug


       selection - Manipulate the X selection


       selection option ?arg arg ...?


       This command provides a Tcl interface to the X selection mechanism and implements the full
       selection functionality described in the X Inter-Client Communication  Conventions  Manual

       Note that for management of the CLIPBOARD selection (see below), the clipboard command may
       also be used.

       The first argument to selection determines the format of the rest of the arguments and the
       behavior of the command.  The following forms are currently supported:

       selection clear ?-displayof window? ?-selection selection?
              If  selection  exists anywhere on window's display, clear it so that no window owns
              the selection anymore.  Selection specifies the X selection that should be cleared,
              and  should  be  an  atom  name  such as PRIMARY or CLIPBOARD; see the Inter-Client
              Communication Conventions Manual  for  complete  details.   Selection  defaults  to
              PRIMARY and window defaults to “.”.  Returns an empty string.

       selection get ?-displayof window? ?-selection selection? ?-type type?
              Retrieves  the value of selection from window's display and returns it as a result.
              Selection defaults to PRIMARY and window defaults to “.”.  Type specifies the  form
              in  which  the selection is to be returned (the desired “target” for conversion, in
              ICCCM terminology), and should be an atom name such as STRING or FILE_NAME; see the
              Inter-Client  Communication Conventions Manual for complete details.  Type defaults
              to STRING.  The selection owner may choose  to  return  the  selection  in  any  of
              several  different  representation  formats,  such  as  STRING,  UTF8_STRING, ATOM,
              INTEGER, etc. (this format is different than the selection type; see the ICCCM  for
              all  the  confusing details).  If the selection is returned in a non-string format,
              such as INTEGER or ATOM, the selection command converts it to string  format  as  a
              collection  of  fields  separated  by  spaces: atoms are converted to their textual
              names, and anything else is converted to hexadecimal integers.  Note that selection
              get does not retrieve the selection in the UTF8_STRING format unless told to.

       selection handle ?-selection s? ?-type t? ?-format f? window command
              Creates  a  handler  for  selection  requests,  such  that command will be executed
              whenever selection s is owned by window and someone attempts to retrieve it in  the
              form  given  by  type  t  (e.g.  t  is  specified in the selection get command).  S
              defaults to PRIMARY, t defaults to STRING, and f defaults to STRING.  If command is
              an  empty  string  then any existing handler for window, t, and s is removed.  Note
              that when the selection is handled as type STRING it is also automatically  handled
              as type UTF8_STRING as well.

              When  selection  is  requested,  window  is  the  selection  owner, and type is the
              requested type, command will be executed as  a  Tcl  command  with  two  additional
              numbers  appended  to  it  (with space separators).  The two additional numbers are
              offset and maxChars:   offset  specifies  a  starting  character  position  in  the
              selection  and  maxChars  gives  the maximum number of characters to retrieve.  The
              command should return a value consisting of at  most  maxChars  of  the  selection,
              starting  at position offset.  For very large selections (larger than maxChars) the
              selection will be retrieved using several invocations of  command  with  increasing
              offset values.  If command returns a string whose length is less than maxChars, the
              return value is assumed to include all of the remainder of the selection;   if  the
              length of command's result is equal to maxChars then command will be invoked again,
              until it eventually returns a result shorter than maxChars.  The value of  maxChars
              will always be relatively large (thousands of characters).

              If command returns an error then the selection retrieval is rejected just as if the
              selection did not exist at all.

              The format argument specifies the representation that should be  used  to  transmit
              the  selection  to  the  requester (the second column of Table 2 of the ICCCM), and
              defaults to STRING.  If format is STRING, the selection  is  transmitted  as  8-bit
              ASCII  characters  (i.e.   just  in  the  form  returned  by command, in the system
              encoding; the UTF8_STRING format always uses UTF-8 as its encoding).  If format  is
              ATOM,  then the return value from command is divided into fields separated by white
              space;  each field is converted to its atom value, and the  32-bit  atom  value  is
              transmitted  instead of the atom name.  For any other format, the return value from
              command is divided into fields separated by white space and each field is converted
              to  a  32-bit  integer;   an  array  of  integers  is  transmitted to the selection

              The format argument is needed only for compatibility with selection requesters that
              do  not  use  Tk.   If Tk is being used to retrieve the selection then the value is
              converted back to a string at the requesting end, so format is irrelevant.

       selection own ?-displayof window? ?-selection selection?

       selection own ?-command command? ?-selection selection? window
              The first form of selection own returns  the  path  name  of  the  window  in  this
              application  that  owns  selection  on  the  display containing window, or an empty
              string if no window in this application owns the selection.  Selection defaults  to
              PRIMARY and window defaults to “.”.

              The second form of selection own causes window to become the new owner of selection
              on window's display, returning an empty string as result. The  existing  owner,  if
              any,  is notified that it has lost the selection.  If command is specified, it is a
              Tcl script to execute when some other window claims ownership of the selection away
              from window.  Selection defaults to PRIMARY.


       The  text,  entry,  ttk::entry,  listbox, spinbox and ttk::spinbox widgets have the option
       -exportselection.  If a widget has this option set to boolean true,  then  (in  an  unsafe
       interpreter)  a  selection  made  in  the  widget  is automatically written to the PRIMARY

       A GUI event, for example <<PasteSelection>>, can copy the  PRIMARY  selection  to  certain
       widgets.   This  copy is implemented by a widget binding to the event.  The binding script
       makes appropriate calls to the selection command.


       On X11, the PRIMARY  selection  is  a  system-wide  feature  of  the  X  server,  allowing
       communication between different processes that are X11 clients.

       On Windows, the PRIMARY selection is not provided by the system, but only by Tk, and so it
       is shared only between windows of a master interpreter and its unsafe slave  interpreters.
       It  is  not shared between interpreters in different processes or different threads.  Each
       master interpreter has a separate PRIMARY selection that is shared only  with  its  unsafe


       A safe interpreter cannot read from the PRIMARY selection because its selection command is
       hidden.  For this reason the PRIMARY selection cannot be written to the Tk  widgets  of  a
       safe interpreter.

       A  Tk  widget  can  have  its  option  -exportselection set to boolean true, but in a safe
       interpreter this option has no effect: writing from the widget to the PRIMARY selection is

       These  are  security  features.   A  safe  interpreter may run untrusted code, and it is a
       security risk if this untrusted code can read or write the PRIMARY selection used by other


       On  X11  platforms,  one  of the standard selections available is the SECONDARY selection.
       Hardly anything uses it, but here is how to read it using Tk:

              set selContents [selection get -selection SECONDARY]

       Many different types of data may be available for a selection; the  special  type  TARGETS
       allows you to get a list of available types:

              foreach type [selection get -type TARGETS] {
                 puts "Selection PRIMARY supports type $type"

       To  claim  the  selection,  you  must  first  set  up a handler to supply the data for the
       selection. Then you have to claim the selection...
              # Set up the data handler ready for incoming requests
              set foo "This is a string with some data in it... blah blah"
              selection handle -selection SECONDARY . getData
              proc getData {offset maxChars} {
                 puts "Retrieving selection starting at $offset"
                 return [string range $::foo $offset [expr {$offset+$maxChars-1}]]

              # Now we grab the selection itself
              puts "Claiming selection"
              selection own -command lost -selection SECONDARY .
              proc lost {} {
                 puts "Lost selection"




       clear, format, handler, ICCCM, own, selection, target, type