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selection(3tk) | Tk Built-In Commands | selection(3tk) |
NAME¶
selection - Manipulate the X selectionSYNOPSIS¶
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 “.”.
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]
foreach type [ selection get -type TARGETS] { puts "Selection PRIMARY supports type $type" }
# 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 ALSO¶
clipboard(3tk)KEYWORDS¶
clear, format, handler, ICCCM, own, selection, target, type8.1 | Tk |