The cairo drawing API that is needed to replace the older API for drawing (gdk) has sprung a lot of code webs. The whole back-end implementation is required to be changed, partially at some places and a complete re-write at rest.
Either Gtk2 must be retained to use older API to support the current logic/schema in the code of drawing.
Or to shift to cairo and use Gtk3, which is lot of work(re-write) and will take up most of my GSoC time.
This is the discussion that I need to have with my mentor. I’ve asked on the mail and now waiting for the response.
The decision will lie with the mentor as well as the maintainer.