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selection(3) |
User Contributed Perl Documentation |
selection(3) |
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:
- $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.
clear, format, handler, ICCCM, own, selection, target, type
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