Add normalized stack support

[panthony]

Can be configured using:

{
  data: {
    stack: {
      normalize: true
    }
  }
}

Defaults to false.

Closes #142

[panthony]

@kt3k Hello there, I was looking to cache some function returns and I noticed the cache.js file.

Look how it is used I found that this is mostly used by load() through cacheIds but:

1. There are no documentation whatsoever nor issues about this
2. Weird to have a public API passing "cache ids"

Do you know how/if this is used ? Would it be possible to drop the support for it ?

My intent would be to modify the cache interface to be used in more contexts internally.

[codecov-io]

Codecov Report

Merging #2670 into master will decrease coverage by 0.04%. The diff coverage is 80.37%.

@@            Coverage Diff             @@
##           master    #2670      +/-   ##
==========================================
- Coverage   80.13%   80.08%   -0.05%     
==========================================
  Files          57       57              
  Lines        4520     4605      +85     
==========================================
+ Hits         3622     3688      +66     
- Misses        898      917      +19

Impacted Files	Coverage Δ
src/config.js	95.83% <ø> (ø)	:arrow_up:
src/data.load.js	58% <100%> (+1.75%)	:arrow_up:
src/domain.js	93.75% <100%> (+0.07%)	:arrow_up:
src/shape.bar.js	98.66% <100%> (+0.01%)	:arrow_up:
src/cache.js	63.15% <100%> (+26.79%)	:arrow_up:
src/tooltip.js	77.23% <100%> (+0.37%)	:arrow_up:
src/api.data.js	100% <100%> (ø)	:arrow_up:
src/axis.js	97.56% <100%> (ø)	:arrow_up:
src/arc.js	73.33% <50%> (-0.63%)	:arrow_down:
src/shape.js	76.92% <69.23%> (-1.77%)	:arrow_down:
... and 2 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update a4c971c...c54d5cf. Read the comment docs.

[codecov-io]

Codecov Report

Merging #2670 into master will increase coverage by 0.29%. The diff coverage is 94.4%.

@@            Coverage Diff             @@
##           master    #2670      +/-   ##
==========================================
+ Coverage   80.29%   80.58%   +0.29%     
==========================================
  Files          59       59              
  Lines        4537     4631      +94     
==========================================
+ Hits         3643     3732      +89     
- Misses        894      899       +5

Impacted Files	Coverage Δ
src/config.js	95.83% <ø> (ø)	:arrow_up:
src/scale.js	100% <100%> (ø)	:arrow_up:
src/shape.bar.js	98.66% <100%> (+0.01%)	:arrow_up:
src/data.load.js	58% <100%> (+1.75%)	:arrow_up:
src/cache.js	63.15% <100%> (+26.79%)	:arrow_up:
src/domain.js	93.75% <100%> (+0.07%)	:arrow_up:
src/util.js	100% <100%> (ø)	:arrow_up:
src/axis.js	97.58% <100%> (+0.02%)	:arrow_up:
src/tooltip.js	77.23% <100%> (+0.37%)	:arrow_up:
src/arc.js	74.57% <50%> (-0.6%)	:arrow_down:
... and 3 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update bdf12d1...9b94955. Read the comment docs.

[panthony]

Big part of untested added code is to be used when padAngle option will be available (see #2669).

Can't add a test for it right now :/

[kt3k]

@panthony Personally I think these cache APIs don't belong to "public API" and we can change (or replace) them as long as the existing charts work.

[panthony]

@kt3k One of the usage of this cache was "recently" added for gauge, but I think the value could be retrieved another way:

return $$.levelColor($$.cache[id].values[0].value);

Otherwise, the only usage is load({ cacheIds: [] }). But I don't really know how it was (is?) used.

[kt3k]

The example looks great! 👍

[panthony]

@kt3k I added a new exemple of a combinaison chart using stack normalisation per axis basis:

[shaswa]

Hi! Thank you so much for this feature! I'm trying to use normalized stacked bar chart in a project. It works as expected except for the tooltip. The tooltip still shows the original values, instead of normalized or percentage values. Do I need to set anything else to display the tooltip values in percentages?

Edit: Figured out a solution almost as soon as I posted this 😅

tooltip: {
  format: {
    value(value, ratio) {
      return `${ratio * 100}%`;
    },
  },
}