Temporary enable transient-mark-mode for rectangle selection

* lisp/mouse.el (mouse-drag-region-rectangle):
Enable transient-mark-mode during selection (bug#38431).

1 files changed, 4 insertions, 0 deletions

diff --git a/lisp/mouse.el b/lisp/mouse.el
index bc05a35009e..32996b2eded 100644
--- a/lisp/mouse.el
+++ b/lisp/mouse.el
@@ -2007,6 +2007,10 @@ This must be bound to a button-down mouse event."
           (setq dragged t)
           (mouse-minibuffer-check start-event)
           (deactivate-mark)
+          (setq-local transient-mark-mode
+                      (if (eq transient-mark-mode 'lambda)
+                          '(only)
+                        (cons 'only transient-mark-mode)))
           (posn-set-point start-pos)
           (rectangle-mark-mode)
           ;; Only tell rectangle about the exact column if we are possibly