cubicweb-jqplot #2527796 png export: pb with legend containing explicit line breaks [done]

eg. <br>.

This is because it attempts to do line wrapping automatically. We should stop doing that and consider explicit line breaks.

prioritynormal
typebug
done in0.3.0
load0.200
load left0.000
closed by#d58cc0d66822 stop auto-wrapping of text, consider explicit line breaks (<br>) instead. Closes #2527796