Chart

Chart is one of Pablo's display functional units.  It accepts as input a
single scalar value and draws consecutive incoming values forward in time
along a line (similar to the Athena stripchart used by xload).  The current
data value and also the largest value seen so far are shown above the plot
area.

Functional Unit Attributes:  scalar

Chart attributes:

	XtNheight	height (in pixels) of the widget
	XtNwidth        width (in pixels) of the widget
	XtNautoscale	set to TRUE if autoscaling is to be done 
	XtNbackground	color of the drawing area background
	XtNdata		color of the shading used below the plot line
	XtNinfoline	set to TRUE if a separate line is to be drawn 
			     which tracks the incoming data values
	XtNmarker	color of the info line
	XtNpassive	(not used)
	XtNscale	the maximum value represented by the widget at
			     the current autoscale setting
	XtNupdate	update interval (not implemented)
