TrendNode calculates space requirement for the legend incorrectly in single axis mode
VertRuler.getWidth() estimates required extra_width as 15.0 * extra_labels.size() if the extra_width has not already been calculated in VertRuler.doRender(..).
VertRuler.doRender(..) in turn calculates the extra_width using real font size and gaps the maximum number of extra labels to spec.singleAxisShowLegendsMaxLegends.
Obviously VertRuler.getWidth() is used for calculating the trend size before performing VertRuler.doRender(..). This results variable amount of extra white space on the right side of legend. The problem is very evident if there are more than 10 trend lines (default value for spec.singleAxisShowLegendsMaxLegends).
This problem arises at least in non-interactive mode.