This documents the built-in PAPCO slice function

;* The "mouse views slice" function uses the time returned by PAPCO and the
;* get_data_call specified for the plot_type to read the data and to draw a 
;* slice at the clicked position. This is commonly used in spectra color plots 
;* to draw a spectrum at that time, or a pitch angle distribution etc, or to
;* call up any other plot at that time as specified by the user. 
;* -> user defined interface routine needed, template included in 
;* $PAPCO_modules/plot_type/papco_interface/plot_type_slice.pro

PAPCO provides a standard window when the mouse is clicked in a panel using
this slice function. This window consist of a draw area and two lines for
comments. The user-defined slice function is then called and handed the time
and y-value of the mouse position and the panel number, it is up to the user
to then use this information to draw another plot.

Typically the user routine provides a two-dimensional "slice" through a three
dimensional data plot such as a color spectrogram. The user routine SHOULD
adopt the axis scaling information from the calling panel to scale its own
plot. 

PAPCO constructs a call to the routine "DrawSlice_plot_type", where plot_type
is the name of your module for which this slice type is activated. This
routine normally resides in the file plot_type_slice.pro in
$PAPCO_modules/plot_type/papco_interface/plot_type_slice.pro.
