Build 3.5.0.35 of xlsgen adds support for computing and rendering chart trendlines.
Before this build, xlsgen could pass trendline details to the old chart engine, relying on Microsoft OWC web components (includes a chart renderer), but the new chart engine introduced in 3.5 could not do anything about chart trendlines.
Beginning with this build, trendlines are computed and rendered in the new built-in chart engine. This includes linear, polynomial, logarithm, ... trendline types.
Chart trendlines computed and rendered by xlsgen