NAME¶
Tk::Selection - Manipulate the X selection
SYNOPSIS¶
$widget->
SelectionOption?(
args)?
DESCRIPTION¶
This command provides an interface to the X selection mechanism and implements
the full selection functionality described in the X Inter-Client Communication
Conventions Manual (ICCCM).
The widget object used to invoke the methods below determines which display is
used to access the selection. In order to avoid conflicts with
selection methods of widget classes (e.g.
Text) this set of
methods uses the prefix
Selection. The following methods are currently
supported:
- $widget->SelectionClear?(-selection=>selection)?
- If selection exists anywhere on
$widget '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. Returns an empty
string.
- $widget->SelectionGet?(?-selection=>selection?,?-type=>type?)?
- Retrieves the value of selection from
$widget 's display and returns it as a result.
Selection defaults to PRIMARY.
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, ATOM,
INTEGER, etc. (this format is different than the selection type; see the
ICCCM for all the confusing details).
If format is not STRING then things get messy, the following
description is from the Tcl/Tk man page as yet incompetely translated for
the perl version - it is misleading at best.
If the selection is returned in a non-string format, such as INTEGER or
ATOM, the SelectionGet converts it to a list of perl values: atoms
are converted to their textual names, and anything else is converted
integers.
A goal of the perl port is to provide better handling of different formats
than Tcl/Tk does, which should be possible given perl's wider range of
``types''. Although some thought went into this in very early days of
perl/Tk what exactly happens is still "not quite right" and
subject to change.
- $widget->SelectionHandle(?-selection=>selection?,?-type=>type?,?-format=>format?
callback)
- Creates a handler for selection requests, such that
callback will be executed whenever selection is owned by
$widget 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
callback is an empty string then any existing handler for
$widget, type, and selection is
removed.
When selection is requested, $widget is the
selection owner, and type is the requested type, callback
will be executed with two additional arguments. The two additional
arguments are offset and maxBytes: offset specifies a
starting character position in the selection and maxBytes gives the
maximum number of bytes to retrieve. The command should return a value
consisting of at most maxBytes of the selection, starting at
position offset. For very large selections (larger than
maxBytes) the selection will be retrieved using several invocations
of callback with increasing offset values. If
callback returns a string whose length is less than
maxBytes, the return value is assumed to include all of the
remainder of the selection; if the length of callback's result is
equal to maxBytes then callback will be invoked again, until
it eventually returns a result shorter than maxBytes. The value of
maxBytes will always be relatively large (thousands of bytes).
If callback returns an error (e.g. via die) 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 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).
If format is not STRING then things get messy, the following
description is from the Tcl/Tk man page as yet untranslated for the perl
version - it is misleading at best.
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 many
selection requesters, except Tcl/Tk. If Tcl/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.
A goal of the perl port is to provide better handling of different formats
than Tcl/Tk does, which should be possible given perl's wider range of
``types''. Although some thought went into this in very early days of
perl/Tk what exactly happens is still "not quite right" and
subject to change.
- $widget->SelectionOwner?(-selection=>selection)?
- SelectionOwner returns the window in this
application that owns selection on the display containing
$widget, or an empty string if no window in this
application owns the selection. Selection defaults to PRIMARY.
- $widget->SelectionOwn?(?-command=>callback?,?-selection=>selection?)?
- SelectionOwn causes $widget to
become the new owner of selection on $widget's
display, returning an empty string as result. The existing owner, if any,
is notified that it has lost the selection. If callback is
specified, it will be executed when some other window claims ownership of
the selection away from $widget. Selection
defaults to PRIMARY.
KEYWORDS¶
clear, format, handler, ICCCM, own, selection, target, type