In addition to the primary selection, the X Window System provides a second similar facility known as the secondary selection. Nowadays, few X applications make use of the secondary selection, but you can access it using the following Emacs commands:
Set the secondary selection, with one end at the place where you press
down the button, and the other end at the place where you release it
mouse-set-secondary). The selected text is highlighted, using
secondary-selection face, as you drag. The window scrolls
automatically if you drag the mouse off the top or bottom of the
window, just like
mouse-set-region (see Mouse Commands for Editing).
This command does not alter the kill ring.
Set one endpoint for the secondary selection
mouse-start-secondary); use M-mouse-3 to set the other
end and complete the selection. This command cancels any existing
secondary selection, when it starts a new one.
Set the secondary selection (
with one end at the position you click M-mouse-3, and the other
at the position specified previously with M-mouse-1. This also
puts the selected text in the kill ring. A second M-mouse-3 at
the same place kills the text selected by the secondary selection just
Insert the secondary selection where you click, placing point at the
end of the yanked text (
Double or triple clicking of M-mouse-1 operates on words and lines, much like mouse-1.
mouse-yank-at-point is non-
nil, M-mouse-2 yanks
at point. Then it does not matter precisely where you click, or even
which of the frame’s windows you click on. See Mouse Commands for Editing.