Tk::Selection - Manipulate the X selection
$widget->SelectionOption?(args)?
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:
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.
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.
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.
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.
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.
clear, format, handler, ICCCM, own, selection, target, type