How to access Plot's internal functions for Custom marks (#1836)?

[JelmerBot]

I have been looking through the PR (#1836) and notebook that describe Plot's extensibility. Both documents are super useful to learn what is possible with Plot. I particularly like the possibilities provided by creating custom marks that extend the Mark class. This approach gives freedom to build basically anything, while keeping access to all the cool features Plot provides.

To facilitate writing custom Mark classes, is there a way to access Plot's internal functions from outside code? For example, to use functions from options.js or style.js that are not included in index.js. If not, would it be possible (and acceptable) to create an additional export/package with the relevant internal functions?

I realise this is more of a developer than an end-user question. I also realise Plot's internal functions are subject to change (without notice), but that seems reasonable for plugin / extension development.

[Fil]

Thanks for the feedback! We're limiting the exposure to what we can document and maintain (say, the "white zone"), while ensuring the possibility of making extensions with a well-defined API. We won't open a "gray zone" with functions that would be half-documented and half-maintained. I understand the pain because I often want to reach for these functions myself when writing plugins or demos, but there's a saying that every undocumented API becomes someone's baseline. If something feels absolutely worth exposing, we'll have to think about moving it to the white zone.

[JelmerBot]

Thanks for your answer! This sounds like a well considered, realistic decision. If extension-development becomes a larger priority in the future, then indeed, I would welcome increasing that exposed zone, even if parts are given fewer guarantees than the public API.