Are you thinking about global shared (optionally mutable) state or more about having config per chart context?

Yes, I am thinking about this for a long time. Currently some of the default values are hardcoded, even tough now we have some robust font configuration. But it seems better if we can globally change the default layout of the any newly created chart.
Any thoughts or concerns ?

I think embedding configuration in context object and implementing default for it should do the trick.

Yes, that's nice suggestion. But I really think something may beyond that.

The first time I thought about this is because somebody reports on OSX it doesn't work because FontNotFound error, I want to have a global default fallback font config. But I don't see any motivation for now, especially we have generic font family support and switched to font-kit, a better maintained font loading crate.

But I am stilling thinking another thing: currently we need to call DrawingArea::fill before drawing especially for backend. I think this is a little bit annoying.
Also I feel annoying for each time I need to disable the mesh line, but at the same time I feel a little bit hesitated to turn it off by default.

All this things make me think we should have a global table for configurations - But haven't come up with a concrete idea.