Globals:
extern int        mse_xin      /* x-input coordinate */
extern int        mse_yin      /* y-input coordinate */
extern int        prscnt[2]    /* array for count of button presses */
extern int        x_lstprs[2]  /* array of x-coords at last press */
extern int        y_lstprs[2]  /* array of y-coords at last press */
extern int        rlscnt[2]    /* array for count of button releases */
extern int        x_lstrls[2]  /* array of x-coords at last release */
extern int        y_lstrls[2]  /* array of y-coords at last release */
extern int        h_micks      /* horizontal motion counter */
extern int        v_micks      /* vertical motion counters */