= [wiki:Development/cabb-upgrade/]PGFLAG =

== Specification ==

We want a simple PGPLOT-based utility to
 * display UV data from a single baseline, in the format
   * channel number on X axis
   * time on Y axis
   * amplitude or phase shown as "greyscale"
 * display a cursor with 'live' readback of the amplitude/phase, channel number, frequency and timestamp

We want to use this to select subsets of the displayed data and apply flagging commands to the subset.

Display characteristics:
 * display one baseline at a time
 * we want to be able to jump to a different baseline number (forward and back thro' the sequence)
 * don't average time steps by default (make the averaging a command parameter)
 * do sum the channels such that the entire bandpass fits in the PGPLOT display window (allow turning this off via command line params)
 * if the uvdata array extends beyond the edges of the display window, allow scrolling (vertically or horizontally)
 * when it is possible to scroll, show an arrow (outside the display grid) (with the shortcut key letter shown as well ?)
 * arrow keys are the most obvious shortcut key!
 * the cursor would ideally be an 'open plus' shape - lines extending to the edge of the display grid but with a small open area at the intersection so you can see what is directly under the cursor.
 * zooming - allow zooming up to 1:1 display. May be useful to have higher zooms than this?
 * must support SELECT and LINE keywords

Flagging:
 * when user selects a piece of data, and says 'flag it'
   * update the display to show the data flagged away
   * allow 'undo' of the last flagging command.
 * selection:
   * by area (PGPLOT boxing)
   * this will do single rows and columns as well.
 * should be able to abort a flagging session, ie throw all flags for the current baseline.
 * probably want to use temporary flagging files that only replace the flag file for the dataset at the end of the task
 * probably want to allow logging of the flagging commands so they can be played back/edited with UVFLAG



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[wiki:Development]