The ideal meaning of Rendering system should be a system which handles rendering of any character/characters in the various editors which provides input mechanism for the user in native languages. So in that sense, it should be The Rendering Engine itself only, like Harfbuzz, Pango, ICU etc and these are well established and well known to the community members. So, I think, he might be looking for a system which can test the Rendering or the Rendering test or reference system, as far as testing and QA is concern. So, it would be better to request the commenter what has exactly been referred to. I just demonstrated what the commenter might mean to say.

Satya
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Satyabrata Maitra
Quality Engineer
Red Hat, Inc
PNQ
+919860140303
smaitra@redhat.com
A well-directed imagination is the source of great deeds