Group bars, but don't stack them

[ilgiz-badamshin]

It's possible to group bars, but don't stack them?
This work with xAxes.stacked = true and yAxes.stacked = false in version 2.4.0: https://jsfiddle.net/tcc6bLdn/
But in master another behavior : https://jsfiddle.net/5xo8rp9f/1/

[etimberg]

This is likely caused by #3563

[potatopeelings]

@etimberg - you're right.

Specifically, the removal of this line

Chart.js/src/controllers/controller.bar.js

Line 156 in 5387c48

return xScale.options.stacked ? ruler.categoryWidth * xScale.options.barPercentage : ruler.barWidth;

and this block

Chart.js/src/controllers/controller.bar.js

Lines 182 to 184 in 5387c48

	if (xScale.options.stacked) {
	return leftTick + (ruler.categoryWidth / 2) + ruler.categorySpacing;
	}

(and their horizontal equivalents) is what caused this.

I had removed it assuming it was a bug because this use case was not immediately obvious and also since the reverse (vertical stacking without stacking x) didn't seem valid. That said, is this a common use case? In the absence of a 3rd dimension, it causes a few problems (the smaller bar being hidden if it's behind the larger one, bar level tooltips not working, being mistaken for a stacked chart). On a related note, the last chart at http://peltiertech.com/overlapped-bar-chart-longer-bars-in-back/ does something similar but without the associate problems by controlling the individual bar widths.

ilgiz-badamshin's chart works around the 1st and 3rd problems by using transparency (the 3rd color that is not in the legend, indicates the areas of overlap)

[etimberg]

Hmmm, I think that both of those cases (stacking X but not Y and vice versa) have been used. I do know that the stacked Y only does make something that sort of looks like a waterfall chart.

I agree that it causes problems. The overlapped bar chart is almost a new chart type because it would need to sort the draw order to put largest bar at the back.

[potatopeelings]

Ah ok! I'll add that back then. I recall there was some thread where the waterfall was going to be implemented as a plug in, but now that you mention it, doing it here is better. I'll add back the lines I removed so that we have this functionality (waterfall) back.

I don't see any code in the original to put the largest bar in the back - if it's easy enough I'll add it, otherwise (and I'm guessing its otherwise - because I don't see a nice place to sort elements in the bar controller) we'll probably need a separate issue for these layered bars (to push the taller ones to the back).

[etimberg]

Awesome 😄 Thanks so much for looking at this. I know you've done a couple of great features now (horizontal bars, group stacked bars) would you be interested in helping maintain?

I don't think it's easy to sort the bars because that would involve changing how datasets draw (right now the datasets draw in order) so it's definitely a separate issue.

[potatopeelings]

PR submitted (just added the lines back and add a new test).

@ilgiz-badamshin - sorry about that!

@etimberg - there's a couple of plugins I'm working on right now - I'll probably have a bit more time after I'm done with those. I just pick up Issues and sort them out / fix them, yes?

[etimberg]

Yup, that's the idea :)

[etimberg]

Pr in #3899

[samy2k01]

Great, grouping bars without stacking is an excellent feature. Looking forward to the fix. Cheers guys.

[etimberg]

Fixed in #3899