selection(n) Tk Built-In Commands selection(n)______________________________________________________________________________NAMEselection - Manipulate the X selectionSYNOPSISselection 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 Communi‐
cation 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 win‐
dow defaults to ``.''. Type specifies the form in which the
selection is to be returned (the desired ``target'' for conver‐
sion, in ICCCM terminology), and should be an atom name such as
STRING or FILE_NAME; see the Inter-Client Communication Conven‐
tions 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, 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 tex‐
tual names, and anything else is converted to hexadecimal inte‐
gers.
selection handle ?-selection selection? ?-type type? ?-format format?
window command
Creates a handler for selection requests, such that command will
be executed whenever selection is owned by window and someone
attempts to retrieve it in the form given by type (e.g. type is
specified in the selection get command). Selection defaults to
PRIMARY, type defaults to STRING, and format defaults to STRING.
If command is an empty string then any existing handler for win‐
dow, type, and selection is removed.
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 max‐ │
Chars: 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 didn't exist at all.
The format argument specifies the representation that should be
used to transmit the selection to the requester (the second col‐
umn of Table 2 of the ICCCM), and defaults to STRING. If format
is STRING, the selection is transmitted as 8-bit ASCII charac‐
ters (i.e. just in the form returned by command). 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 selec‐
tion requesters that don't 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 SEC‐
ONDARY 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 spe‐
cial 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}]]
}
# Now we grab the selection itself
puts "Claiming selection"
selection own -command lost -selection SECONDARY .
proc lost {} {
puts "Lost selection"
}
SEE ALSOclipboard(n)KEYWORDS
clear, format, handler, ICCCM, own, selection, target, type
Tk 8.1 selection(n)
