29.20 Window System Selections
In window systems, such as X, data can be transferred between different applications by means of selections. X defines an arbitrary number of selection types, each of which can store its own data; however, only three are commonly used: the clipboard, primary selection, and secondary selection. Other window systems support only the clipboard. See Cut and Paste in The GNU Emacs Manual, for Emacs commands that make use of these selections. This section documents the low-level functions for reading and setting window-system selections.
command gui-set-selection type data​
This function sets a window-system selection. It takes two arguments: a selection type type, and the value to assign to it, data.
type should be a symbol; it is usually one of PRIMARY, SECONDARY or CLIPBOARD. These are symbols with upper-case names, in accord with X Window System conventions. If type is nil, that stands for PRIMARY.
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.
This function returns data.
function gui-get-selection \&optional type data-type​
This function accesses selections set up by Emacs or by other programs. 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 program into Lisp data. Meaningful values include TEXT, STRING, UTF8_STRING, TARGETS, LENGTH, DELETE, FILE_NAME, CHARACTER_POSITION, NAME, LINE_NUMBER, COLUMN_NUMBER, OWNER_OS, HOST_NAME, USER, CLASS, ATOM, and INTEGER. (These are symbols with upper-case names in accord with X conventions.) The default for data-type is STRING. Window systems other than X usually support only a small subset of these types, in addition to STRING.
user option selection-coding-system​
This variable specifies the coding system to use when reading and writing selections or the clipboard. See Coding Systems. The default is compound-text-with-extensions, 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. gui-get-selection and gui-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. The supported data type is STRING.
For backward compatibility, there are obsolete aliases x-get-selection and x-set-selection, which were the names of gui-get-selection and gui-set-selection before Emacs 25.1.