[BioC] GViz Annotation Track Stacking

[Lance Parsons]

I've recently started using the option to put group labels below the 
features in Gviz 1.8.1 AnnotationTracks (just.group="below").  However, 
I have noticed that when the label is larger than the feature, the  
stacking algorithm does not move the features onto a separate line as it 
does when justification is to the left.  See the example photos:

just.group="left": http://imgur.com/VfUN3G0

just.group="below": http://imgur.com/zmRGtxD

I have been putting the labels below since that often makes it clearer 
which feature is being labeled (at least in my cases with small 
features). I'd be willing to help work on a patch for this, but could 
use a little help finding the relevant code.  It'd be great to update 
the stacking code to account for label widths below the feature as well 
as to have an option to control the spacing when a label is to the left 
(or right) of a feature.

-- 
Lance Parsons - Scientific Programmer
134 Carl C. Icahn Laboratory
Lewis-Sigler Institute for Integrative Genomics
Princeton University