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



______________________________________________________________________________

NAME
       selection - Manipulate the X selection

SYNOPSIS
       selection option ?arg arg ...?
______________________________________________________________________________

DESCRIPTION
       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 (ICCCM).

       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 requester.

              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.

EXAMPLES
       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"
              }

SEE ALSO
       clipboard(n)

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



Tk                                    8.1                         selection(n)
