Add support for reversing a grouped category title on tooltips

[lambk]

• Setting the new reverseTitle option on the chart.tooltip object will result in the tooltip title being displayed as <high_level_category>, <middle_level_category>, <low_level_category> rather than the default low to high order

• If the option is omitted, it defaults to false

Let me know if there are other preferences on the option name or how it is obtained

[KacperMadej]

Changes like that could be done through tooltip formatter, so I believe the option is redundant and will be merged only if more requests for this features will be made. This PR could be used to track how popular is the feature, so I'm not closing it either.

[dmitrygorbenko]

Hi everyone,

I was working on this issue today and I almost was ready to submit the same MR.

@KacperMadej I'd like to know how it's possible to achieve this reverse after the string was joined with commas.
I mean, if I try to split the string back by commas, I can have issues if one of the parts contained comma.
Like, if I have ['A', 'B', 'C, D'] (3 items) and I join them by commas I'll get string 'A, B, C, D'.
And if I try to split it back I'll get ['A', 'B', 'C', 'D'] (4 items).
So the reverse should be done before joining.
But maybe I'm missing something and you can help us ?

I'd love to see this code being merged and used by everyone.

Thanks,
Dima

[dmitrygorbenko]

But at the same time I'd like to pass 'options' variable instead of 'reverseTooltipTitle' to Category class, so in the future more options can be passed there. I think I'm going to create my own MR from this idea.

[dmitrygorbenko]

So, I've created another MR #187
which does the same but passes object instead of one variable, and here is the sample of usage:

Highcharts({
	...
	tooltip: {
		...
		reverseTitle: true
	}
})

and this tooltip object is available inside the Category class as this.tooltipOptions variable.

I hope you find this useful and consider adding such ability to your code.

Thanks