Event annotations, API and chart UI for time series markup B)

[goodboy]

This has been a todo for quite some time and recently we've had a lot of lurkerz and even some of our devs ask about it.

It's a feature that is like it sounds, a subsys for arbitrary annotation of our charts from time-based events (normally stuff from the nooz).

there are plenty of existing charting platforms that have this for reference:

• tinaview
• webull
• ib's tws

---

where to start in the code base:

• we already have a time-slicing api in: https://github.com/pikers/piker/blob/master/piker/data/_pathops.py#L294 (which was implemented as part of getting multi-timeseries overlays working.
• we already have a chart annotation API as part of our order mode system:
  • order mode usage: https://github.com/pikers/piker/blob/master/piker/ui/order_mode.py#L537
  • actual graphics apis: ArrowEditor: https://github.com/pikers/piker/blob/master/piker/ui/_editors.py#L57

We mostly just need a public API for unifying these systems and obviously some helper routines for parsing some input to its timestamp and content and then displaying it with some set of options for graphical shapes to draw.

Probably much more to come in this writeup B)