Do not steal primary selection on mark deactivation.

* lisp/simple.el (deactivate-mark): Do not set the primary selection
if another program has acquired it.

Fixes: debbugs:11772

2 files changed, 10 insertions, 1 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 70894c5fc7b..8a608ea7b10 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,8 @@
+2012-07-08  Chong Yidong  <cyd@gnu.org>
+
+        * simple.el (deactivate-mark): Do not set the primary selection
+        if another program has acquired it (Bug#11772).
+
 2012-07-07  Kevin Ryde  <user42@zip.com.au>
 
         * woman.el (woman-strings): Fix double-quote handling (Bug#1151).
diff --git a/lisp/simple.el b/lisp/simple.el
index 4527a9da0dc..e6b4a79b9b2 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -3863,7 +3863,11 @@ run `deactivate-mark-hook'."
       (cond (saved-region-selection
              (x-set-selection 'PRIMARY saved-region-selection)
              (setq saved-region-selection nil))
-            ((/= (region-beginning) (region-end))
+            ;; If another program has acquired the selection, region
+            ;; deactivation should not clobber it (Bug#11772).
+            ((and (/= (region-beginning) (region-end))
+                  (or (x-selection-owner-p 'PRIMARY)
+                      (null (x-selection-exists-p 'PRIMARY))))
              (x-set-selection 'PRIMARY
                               (buffer-substring-no-properties
                                (region-beginning)