getPixelForTick is confusing and possibly inconsistent

[benmccann]

It looks to me like sometimes it's doing getPixelForTick and sometimes it's doing something more akin to getPixelForIndex. This gets especially confusing in certain cases like when autoSkip is enabled or you have auto tick generation on the time scale where ticks and indexes don't map 1:1.

[kurkle]

I can't seem to find where its used akin to getPixelForIndex?

I'd keep the data separated from scale interface - so scale does not need to know how data is input, parsed or stored internally by the controllers.

If getPixelForIndex is required, it should be placed in controller. But I'd rather not have such a method, it does not make sense if data is object:

data: { Jan: {o: 10, h: 11, c: 9, l: 8}, Feb: ...}

[etimberg]

I think getPixelForTick acts like getPixelForIndex in the category scale where that's by design

[benmccann]

The main reason I'm confused is that when we autoSkip we pass in tick._index, which is the original index before the autoSkip happened (getPixelForGridLine is a wrapper around getPixelForTick):

Chart.js/src/core/core.scale.js

Line 1014 in a3392e0

lineValue = getPixelForGridLine(me, tick._index || i, offsetGridLines);

[etimberg]

That may be because for the longest time, the auto skip was just not drawing the ticks. Now that we reduce the tick array into the smaller to draw array, I think we should pass the index in that array