Opt-out from subchart DOM if not enabled

[panthony]

This PR does several things:

• do not append DOM's nodes for subchart if not enabled (Closes Rotated chart with hidden subchart still able to interact with #2503 and first step for Performance issues with c3js #2303)
• correct the 'undefined' height (Closes Valid svg subchart error (+fix) #2112)
• Add show/hide API methods (Closes hide/show subchart ? #358)

[codecov-io]

Codecov Report

Merging #2674 into master will increase coverage by 0.01%.
The diff coverage is 96.87%.

@@            Coverage Diff            @@
##           master   #2674      +/-   ##
=========================================
+ Coverage   80.29%   80.3%   +0.01%     
=========================================
  Files          59      60       +1     
  Lines        4537    4565      +28     
=========================================
+ Hits         3643    3666      +23     
- Misses        894     899       +5

Impacted Files	Coverage Δ
src/core.js	89.95% <100%> (-0.16%)	⬇️
src/data.js	84.7% <100%> (+0.18%)	⬆️
src/subchart.js	87.5% <100%> (-1.39%)	⬇️
src/api.subchart.js	91.66% <91.66%> (ø)

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[panthony]

@kt3k I just don't get it, I installed from scratch RVM, bundler, etc.. from the 0.7.3 tag and the documentation site served by watch:docs does not work.

I have a wonderful NameError: uninitialized constant #<Class:0x00007fdfd8214c78>::EXPR_BEGEXPR_BEGEXPR_BEGEXPR_BEGEXPR_CMDARGEXPR_DOTEXPR_ARGEXPR_BEG error located here:

%a( href="##{ id.gsub(/\./, '-') }")< #{ id.gsub(/(api|class)\./, '') }

I played around and the issue is with %a() .. maybe it misses id ? Result of a breaking change due to an unwanted update ?

I really have no clue I have 0 knowledge of the stack used to generate the doc.

[kt3k]

@panthony Which ruby version do you use? You need ruby 2.4.4 for building the current document site (I think it can't be built with ruby 2.5 or above).

[panthony]

@kt3k I'll check that on monday, I do not have my laptop with me this week-end but I'll likely have the most recent version of ruby.

Good to know I should not have a version too recent, thanks :)

edit:

Annnnnd it was clearly stated in CONTRIBUTING.md:

Note: Currently the site doesn't build with ruby 2.5.x, so you need ruby 2.4.4 or below. ([rbenv][] is useful for switching between ruby versions.)

Maybe one day I'll learn to fully read something 🥇