hs_plot::locate

Source: plotting/hs_plot__locate.pro

 HS_PLOT::LOCATE
        Mark one or more positions on a single plot.

 Usage:
        postions=hs_plot::locate([dataset, /one_value, /force])

 Argument:
        dataset objref  input   A dataset reference to use in place of
                                the current dataset.

 Keywords:
        one_value ?     input   If set, then just read a single value
                                and exit.
        force                   If set, then override all locks about
                                dataset status (DANGEROUS).
        nomain                  If set, then don't save (or even offer
                                to) the values to $MAIN$

 Restrictions:
        A single plot against time must be present, and the device
        must support cursor reading.

 History:
        Original: 24/5/94; SJT
        Extend to multi-panel and non-time plots: 1/6/94; SJT
        Return all marked positions: 25/4/95; SJT
        Add check & warning for PHA matrix plots: 23/11/95; SJT
        Convert to plot object method: 5,6/6/00; SJT
        Add dataset argument: 7/0/00; SJT
        Add force keyword: 14/11/00; SJT
        Replace !err with !mouse.button: 24/11/00; SJT
        Return a valid but null position if the first click is M3:
        28/11/00; SJT
        Fix colours so the cross-hairs show in 24-bpp: 6/2/01; SJT
        Add nomain keyword: 12/2/02
        Add stuff to convert xflare Y's to dates: 7/6/02; SJT