There are other kinds of X selections besides the Primary selection; one common one is the Clipboard selection. Some applications prefer to transfer data using this selection in preference to the Primary. One can transfer text from the Primary selection to the Clipboard selection with the Copy command under the Edit menu in the menubar.
Usually, the clipboard selection is not visible. However, if you run the
xclipboard application, the text most recently copied to the clipboard
(with the Copy command) is displayed in a window. Any time new text is
thus copied, the xclipboard application makes a copy of it and displays
it in its window. The value of the clipboard can survive the lifetime of the
running Emacs process. The
xclipboard man page provides more details.
Warning: If you use the xclipboard application, remember that it
maintains a list of all things that have been pasted to the clipboard (that
is, copied with the Copy command). If you don’t manually delete elements
from this list by clicking on the Delete button in the
window, the clipboard will eventually consume a lot of memory.
In summary, some X applications (such as xterm) allow one to paste text in them from SXEmacs in the following way:
With some other applications (notably, the OpenWindows and Motif tools) you must use this method instead: