A key sample for pm3d surfaces?

[Daniel J S. <dan...@ie...>]

I'm trying to add a key sample for a pm3d surface.  I know there is the 
color box and all, but it seems odd that there can be a title entry in 
the key but no sample.  I can sort of kludge a solution by leaving the 
surface title empty and then create a bogus line with NaN's that will 
contain the sample and title, linewidth 8.  For the Qt terminal, the 
default is rounded line ends so the key sample at linewidth 8 is round.

Basically, it would be nice to have a sample entry for surface similar 
in appearance to the filledcurve or candlestick of 2D plots.  I wonder 
if it would make sense to have a "sample" descriptor in plot/splot lines 
similar to the "title" descriptor.

Dan