stack-mixin: setting custom stack layout algorithm not working

[jetsnguns]

The chart.stackLayout method is not working correctly when you try to change the layout algorithm. Unlike its default initialization on line 28 of stack-mixin.js:

    var _stackLayout = d3.layout.stack()
        .values(prepareValues);

the method code on line 263 lacks binding values:

    _stackLayout = stack;

Changing it to

     _stackLayout = stack.values(prepareValues);

fixes the issue (tested with d3.layout.stack().offset("expand")).

[gordonwoodhull]

Documentation link for d3.layout.stack.values:
https://github.com/mbostock/d3/wiki/Stack-Layout#values

[gordonwoodhull]

Cool! Does this mean that we have normalized stacked bar charts?

I agree - although this feature goes back to the very early days of dc.js, it doesn't look like it could ever have worked without specifying .values().

I'm not sure if it's a good idea, but in case anyone is intentionally setting .values() differently, we could check if it is already set and only set it if not:

     _stackLayout = stack;
     if(_stackLayout.values() === d3.layout.stack().values()) {
          _stackLayout.values(prepareValues);

Kinda ugly though. The default is d3_identity but that's not exposed.

[gordonwoodhull]

I'm fixing this in 2.0 beta 28 - unfortunately I don't have time to implement tests for a different stack layout and stackLayout remains untested. 😦