path: root/doc/clipboard.n

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'\" RCS: @(#) $Id: clipboard.n,v 1.20 2010/03/04 13:32:20 dkf Exp $
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.so man.macros
.TH clipboard n 8.4 Tk "Tk Built-In Commands"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
clipboard \- Manipulate Tk clipboard
.SH SYNOPSIS
\fBclipboard \fIoption\fR ?\fIarg arg ...\fR?
.BE
.SH DESCRIPTION
.PP
This command provides a Tcl interface to the Tk clipboard,
which stores data for later retrieval using the selection mechanism 
(via the \fB\-selection CLIPBOARD\fR option).
In order to copy data into the clipboard, \fBclipboard clear\fR must
be called, followed by a sequence of one or more calls to \fBclipboard
append\fR.  To ensure that the clipboard is updated atomically, all
appends should be completed before returning to the event loop.
.PP
The first argument to \fBclipboard\fR determines the format of the
rest of the arguments and the behavior of the command.  The following
forms are currently supported:
.TP
\fBclipboard append\fR ?\fB\-displayof\fR \fIwindow\fR? ?\fB\-format\fR \fIformat\fR? ?\fB\-type\fR \fItype\fR? ?\fB\-\|\-\fR? \fIdata\fR
.
Appends \fIdata\fR to the clipboard on \fIwindow\fR's
display in the form given by \fItype\fR with the representation given
by \fIformat\fR and claims ownership of the clipboard on \fIwindow\fR's
display.
.RS
.PP
\fIType\fR specifies the form in which the selection is to be returned
(the desired
.QW target
for conversion, in ICCCM terminology), and
should be an atom name such as \fBSTRING\fR or \fBFILE_NAME\fR; see the
Inter-Client Communication Conventions Manual for complete details.
\fIType\fR defaults to \fBSTRING\fR.
.PP
The \fIformat\fR 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 \fBSTRING\fR.  If \fIformat\fR is
\fBSTRING\fR, the selection is transmitted as 8-bit ASCII characters.  If
\fIformat\fR is \fBATOM\fR, then the \fIdata\fR 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 \fIformat\fR,  \fIdata\fR 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.  Note that strings passed to
\fBclipboard append\fR are concatenated before conversion, so the
caller must take care to ensure appropriate spacing across string
boundaries.  All items appended to the clipboard with the same
\fItype\fR must have the same \fIformat\fR.
.PP
The \fIformat\fR argument is needed only for compatibility with
clipboard requesters that do not use Tk.  If the Tk toolkit is being
used to retrieve the \fBCLIPBOARD\fR selection then the value is
converted back to a string at the requesting end, so \fIformat\fR is
irrelevant.
.PP
A \fB\-\|\-\fR argument may be specified to mark the end of options:  the
next argument will always be used as \fIdata\fR.
This feature may be convenient if, for example, \fIdata\fR starts
with a \fB\-\fR.
.RE
.TP
\fBclipboard clear\fR ?\fB\-displayof\fR \fIwindow\fR?
.
Claims ownership of the clipboard on \fIwindow\fR's display and removes
any previous contents.  \fIWindow\fR defaults to
.QW . .
Returns an empty string.
.TP
\fBclipboard get\fR ?\fB\-displayof\fR \fIwindow\fR? ?\fB\-type\fR \fItype\fR?
.
Retrieve data from the clipboard on \fIwindow\fR's display.
\fIWindow\fR defaults to
.QW . .
\fIType\fR specifies the form in which
the data is to be returned and should be an atom name such as \fBSTRING\fR
or \fBFILE_NAME\fR.  \fIType\fR defaults to \fBSTRING\fR.  This command is
equivalent to
.QW "\fBselection\fR \fBget \-selection CLIPBOARD\fR" .
.RS
.PP
Note that on modern X11 systems, the most useful type to retrieve for
transferred strings is not \fBSTRING\fR, but rather \fBUTF8_STRING\fR.
.RE
.SH EXAMPLES
.PP
Get the current contents of the clipboard.
.CS
if {[catch {\fBclipboard get\fR} contents]} {
    # There were no clipboard contents at all
}
.CE
.PP
Set the clipboard to contain a fixed string.
.CS
\fBclipboard clear\fR
\fBclipboard append\fR "some fixed string"
.CE
.PP
You can put custom data into the clipboard by using a custom \fB\-type\fR
option. This is not necessarily portable, but can be very useful. The
method of passing Tcl scripts this way is effective, but should be mixed
with safe interpreters in production code.
.CS
# This is a very simple canvas serializer;
# it produces a script that recreates the item(s) when executed
proc getItemConfig {canvas tag} {
   set script {}
   foreach item [$canvas find withtag $tag] {
      append script {$canvas create } [$canvas type $item]
      append script { } [$canvas coords $item] { }
      foreach config [$canvas itemconf $item] {
         lassign $config name \- \- \- value
         append script [list $name $value] { }
      }
      append script \en
   }
   return [string trim $script]
}

# Set up a binding on a canvas to cut and paste an item
set c [canvas .c]
pack $c
$c create text 150 30 \-text "cut and paste me"
bind $c <<Cut>> {
   \fBclipboard clear\fR
   \fBclipboard append \-type\fR TkCanvasItem \e
         [getItemConfig %W current]
   # Delete because this is cut, not copy.
   %W delete current
}
bind $c <<Paste>> {
   catch {
      set canvas %W
      eval [\fBclipboard get \-type\fR TkCanvasItem]
   }
}
.CE
.SH "SEE ALSO"
interp(n), selection(n)
.SH KEYWORDS
clear, format, clipboard, append, selection, type
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