Support setting region from secondary selection and vice versa

* lisp/mouse.el (secondary-selection-exist-p): New function to
allow callers to tell existence of the secondary selection
in current buffer.
(secondary-selection-to-region): New function to set
beginning and end of the region from those of the secondary
selection.
(secondary-selection-from-region): New function to set
beginning and end of the secondary selection from those of
the region.  (Bug#27530)

* etc/NEWS: Mention the new functions.

1 files changed, 7 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index a685a9fbe92..280ab64f37c 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1819,6 +1819,13 @@ can be replicated simply by setting 'comment-auto-fill-only-comments'.
 ** New pcase pattern 'rx' to match against a rx-style regular expression.
 For details, see the doc string of 'rx--pcase-macroexpander'.
 
+---
+** New functions to set region from secondary selection and vice versa.
+The new functions 'secondary-selection-to-region' and
+'secondary-selection-from-region' let you set the beginning and the
+end of the region from those of the secondary selection and vise
+versa.
+
 
 * Changes in Emacs 26.1 on Non-Free Operating Systems