Can we use this PR to talk about the proposed API and the need for it? There are so many other issues and PRs that I am having trouble following what has been said where.

I'd really appreciate a few examples as to what this new feature is supposed to look like to the end user, and a bit more discussion as to whether this is worth the complexity. It seems there is one use case where its "lets let the user normalize the unit size of markers given a limited set of options" all the way to "lets let the user arbitrarily transform markers using the full transform stack". Perhaps these are not incompatible, but it would be nice to see what this will look like by the end of all these PRs.

Right now the only example I've seen in any of the PRs is the quite esoteric desire to lay out pies charts usingscatter, which is pretty gee-whiz, but doesn't strike me as a good argument for any of this functionality. Are there examples that show the power of this approach for actual scatter plots?

@jklymak absolutely! Opened this PR to centralize discussion since, as you say, it was pretty fractured before.

I'll let@ImportanceOfBeingErnest speak for the use cases for custom paths for a marker, but we already allow custom paths for markers, that is existing API.

This PR is not about allowing custom markers, but allowing us to normalize markers so that they look perceptually uniform (#15703).

Since we already allow custom markers, any marker normalization code has to be able to perform its duties when passed an arbitrary path. Thankfully, the formulas for the area/extents/etc of an arbitrary path are actually quite simple (thanks to the fact that ourPath objects are just a list of bezier curves), so this PR solves the normalization problem by just implementing the code to compute the area/bbox area/etc of an arbitrary path.

Is the issue that you don't see a use-case for custom markers? We'd have to remove existing 3.2.x API to get rid of them. (Although the changes in this PR would go in more or less as-is regardless).

There is a section "Why is this useful?" in my PR#16773.

Just found this issue and wanted to offer my encouragement. It looks like it's going to take substantial effort, but I think it would be a really big improvement.

Since this Pull Request has not been updated in 60 days, it has been marked "inactive." This does not mean that it will be closed, though it may be moved to a "Draft" state. This helps maintainers prioritize their reviewing efforts. You can pick the PR back up anytime - please ping us if you need a review or guidance to move the PR forward! If you do not plan on continuing the work, please let us know so that we can either find someone to take the PR over, or close it.