framepos_t _start; ///< start frame of the overview
framepos_t _end; ///< end frame of the overview
+ framepos_t _leftmost; ///< the earliest frame we ever viewed
+ framepos_t _rightmost; ///< the latest frame we ever viewed
+
/** fraction of the session length by which the overview size should extend past the start and end markers */
double _overhang_fraction;