29.18 Window System Selections

The X server records a set of selections which permit transfer of data between application programs. The various selections are distinguished by selection types, represented in Emacs by symbols. X clients including Emacs can read or set the selection for any given type.

Function: x-set-selection type data

This function sets a "selection" in the X server. It takes two arguments: a selection type type, and the value to assign to it, data. If data is nil, it means to clear out the selection. Otherwise, data may be a string, a symbol, an integer (or a cons of two integers or list of two integers), an overlay, or a cons of two markers pointing to the same buffer. An overlay or a pair of markers stands for text in the overlay or between the markers.

The argument data may also be a vector of valid non-vector selection values.

Each possible type has its own selection value, which changes independently. The usual values of type are PRIMARY and SECONDARY; these are symbols with upper-case names, in accord with X Window System conventions. The default is PRIMARY.

Function: x-get-selection &optional type data-type

This function accesses selections set up by Emacs or by other X clients. It takes two optional arguments, type and data-type. The default for type, the selection type, is PRIMARY.

The data-type argument specifies the form of data conversion to use, to convert the raw data obtained from another X client into Lisp data. Meaningful values include TEXT, STRING, TARGETS, LENGTH, DELETE, FILE_NAME, CHARACTER_POSITION, LINE_NUMBER, COLUMN_NUMBER, OWNER_OS, HOST_NAME, USER, CLASS, NAME, ATOM, and INTEGER. (These are symbols with upper-case names in accord with X conventions.) The default for data-type is STRING.

The X server also has a set of numbered cut buffers which can store text or other data being moved between applications. Cut buffers are considered obsolete, but Emacs supports them for the sake of X clients that still use them.

Function: x-get-cut-buffer n

This function returns the contents of cut buffer number n.

Function: x-set-cut-buffer string &optional push

This function stores string into the first cut buffer (cut buffer 0). If push is nil, only the first cut buffer is changed. If push is non-nil, that says to move the values down through the series of cut buffers, much like the way successive kills in Emacs move down the kill ring. In other words, the previous value of the first cut buffer moves into the second cut buffer, and the second to the third, and so on through all eight cut buffers.

Variable: selection-coding-system

This variable specifies the coding system to use when reading and writing selections, the clipboard, or a cut buffer. See section 33.10 Coding Systems. The default is compound-text, which converts to the text representation that X11 normally uses.

When Emacs runs on MS-Windows, it does not implement X selections in general, but it does support the clipboard. x-get-selection and x-set-selection on MS-Windows support the text data type only; if the clipboard holds other types of data, Emacs treats the clipboard as empty.

User Option: x-select-enable-clipboard

If this is non-nil, the Emacs yank functions consult the clipboard before the primary selection, and the kill functions store in the clipboard as well as the primary selection. Otherwise they do not access the clipboard at all. The default is nil on most systems, but t on MS-Windows.