+(defcustom mouse-select-region-move-to-beginning nil
+ "Effect of selecting a region extending backward from double click.
+Nil means keep point at the position clicked (region end);
+non-nil means move point to beginning of region."
+ :type '(choice (const :tag "Don't move point" nil)
+ (const :tag "Move point to beginning of region" t))
+ :group 'mouse
+ :version "25.2")
+