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   Zoom-window - Basic PAPCO functionality
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   Use this window to select an area within the panel by clicking the mouse
   and then dragging it. The x-range (time) and y-range chosen is displayed
   in the Zoom Window.

   Once you have chosen your area to be zoomed you have a choice to update
   the time-range, the y-range or both. 

   Updating the time range sets new times in the start time and end time
   sliders in the PAPCO main window. You can also zoom in time only by
   using these sliders in the PAPCO main window. Your plot routine
   can then use the new start and end times to display a subset of the
   data. Times are passed in the COMMOM BLOCK TIME.

   Updating Y sets the relevant entry in the COMMON BLOCK Y-SCALE which can
   be used by your plot routine to set new y-scaling. 
   NOTE: This needs to be supported by your plot routine to work.
