+(defcustom mime-preview-move-scroll nil
+ "*Decides whether to scroll when moving to next entity.
+When t, scroll the buffer. Non-nil but not t means scroll when
+the next entity is within next-screen-context-lines from top or
+buttom. Nil means don't scroll at all."
+ :group 'mime-view
+ :type '(choice (const :tag "Off" nil)
+ (const :tag "On" t)
+ (sexp :tag "Situation" 1)))