clipboard

Name

clipboard — Manipulate Tk clipboard

Synopsis

clipboard option ?arg arg ...?

Description

This command provides a Tcl interface to the Tk clipboard, which stores data for later retrieval using the selection mechanism (via the -selection CLIPBOARD option). In order to copy data into the clipboard, clipboard clear must be called, followed by a sequence of one or more calls to clipboard append. To ensure that the clipboard is updated atomically, all appends should be completed before returning to the event loop.

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

clipboard append ?-displayof window? ?-format format? ?-type type? ?--? data

Appends data to the clipboard on window's display in the form given by type with the representation given by format and claims ownership of the clipboard on window's display.

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 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. If format is ATOM, then the data 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, data 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 clipboard append 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 type must have the same format.

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

A -- argument may be specified to mark the end of options: the next argument will always be used as data. This feature may be convenient if, for example, data starts with a -.

clipboard clear ?-displayof window?

Claims ownership of the clipboard on window's display and removes any previous contents. Window defaults to “.”. Returns an empty string.

clipboard get ?-displayof window? ?-type type?

Retrieve data from the clipboard on window's display. Window defaults to “.”. Type specifies the form in which the data is to be returned and should be an atom name such as STRING or FILE_NAME. Type defaults to STRING. This command is equivalent to “selection get -selection CLIPBOARD”.

Note that on modern X11 systems, the most useful type to retrieve for transferred strings is not STRING, but rather UTF8_STRING.

Examples

Get the current contents of the clipboard.

if {[catch {clipboard get} contents]} {
    # There were no clipboard contents at all
}

Set the clipboard to contain a fixed string.

clipboard clear
clipboard append "some fixed string"

You can put custom data into the clipboard by using a custom -type 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.

# 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 \n
   }
   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>> {
   clipboard clear
   clipboard append -type TkCanvasItem \
         [getItemConfig %W current]
   # Delete because this is cut, not copy.
   %W delete current
}
bind $c <<Paste>> {
   catch {
      set canvas %W
      eval [clipboard get -type TkCanvasItem]
   }
}

See also

interp, selection