UIApexCard TODO

[Habbie]

See #68 for some of the original notes.

• subscribe to entities
• respect various config items (timespan to plot, chart type [line, bar, ...], also data processing like averages)
• expose the full series config to JS so we can handle data processing (like averages) in there instead of C++ in case that's more convenient
• figure out how to handle unknown points (like when you have to plot 48h but only have the next 15h - apexcard just leaves that room empty)
• per-point colours (can apex even do this? I do want it because I have it on Toon for electricity prices. I do recall we'll need LVGL 9 for this)
• better plotting/positioning of the Now pointer (which should also be optional)
• handle multiple series
• handle mixed chart types (line, bar, ...) - I don't think lv_chart currently can, so this might be a bunch of work
• move time handling into JS
• if necessary, figure out how to have voorkant-specific metadata in an apex config. The yaml tree is checked pretty strictly by apexcard, so that's a bad fit. I wonder what happens if we return a third data column?

[cyclops1982]

• Per point colour is not something apexchart in HA does, but i think the actual apexchart can do gradients - https://apexcharts.com/javascript-chart-demos/line-charts/gradient/. I looked at this for the same reason as you have :-)
• I don't think we need it, but better handling of decimals might be useful at some stage (a temperature chart...)

[cyclops1982]

I do not think we want to add handling of multiple HAEntities to this PR, but need to mention that.

[Habbie]

I don't think we need it, but better handling of decimals might be useful at some stage (a temperature chart...)

Oh we absolutely need that. #68 currently just multiplies everything by 1000 to make the graph work at all. The solution appears to be to divide again and (s)printf a bit in a callback.

I do not think we want to add handling of multiple HAEntities to this PR, but need to mention that.

I did leave a FIXME in there, but it's worth a separate issue.