selection

Manipulate the X selection

SYNOPSIS

(selection option ?arg arg ...?)

DESCRIPTION

This procedure provides a STk interface to the X selection mechanism and implements the full selection functionality described in the X Inter-Client Communication Conventions Manual (ICCCM).

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

(selection 'clear ?:displayof window? ?:selection selection?): If selection exists anywhere on window'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 and window defaults to ``.''. Returns an empty list.
(selection 'get ?:displayof window? ?:selection selection? ?:type type?): Retrieves the value of selection from window's display and returns it as a result. Selection defaults to PRIMARY and window defaults to ``*root*''. 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 the selection is returned in a non-string format, such as INTEGER or ATOM, the selection procedure converts it to string format as a collection of fields separated by spaces: atoms are converted to their textual names, and anything else is converted to hexadecimal integers.

(selection 'handle ?:selection selection? ?:type type? ?:format format? window procedure)

Creates a handler for selection requests, such that procedure will be executed whenever selection is owned by window and someone attempts to retrieve it in the form given by type (e.g. type is specified in the selection get procedure). Selection defaults to PRIMARY, type defaults to STRING, and format defaults to STRING. If procedure is an empty string then any existing handler for window, type, and selection is removed.

When selection is requested, window is the selection owner, and type is the requested type, procedure will be applied as a STk procedure with a list of two numbers. The two additional numbers are offset and maxBytes: offset specifies a starting character position in the selection and maxBytes gives the maximum number of bytes to retrieve. The procedure 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 procedure with increasing offset values. If procedure 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 procedure's result is equal to maxBytes then procedure 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 procedure returns an error 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 procedure). If format is ATOM, then the return value from procedure 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 procedure 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 selection requesters that don't use Tk. If 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.

(selection 'own ?:displayof window? ?:selection selection?)

(selection 'own ?:procedure procedure? ?:selection selection? window)

The first form of selection own returns the path name of the window in this application that owns selection on the display containing window, or #f if no window in this application owns the selection. Selection defaults to "PRIMARY" and window defaults to ``*root*''.

The second form of selection own causes window to become the new owner of selection on window's display, returning an empty list as result. The existing owner, if any, is notified that it has lost the selection. If procedure is specified, it is a STk script to execute when some other window claims ownership of the selection away from window. Selection defaults to "PRIMARY".

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