Fix tooltip ordering with data_order and add tooltip_order

[panthony]

This is an attempt to fix various issues around tooltip ordering ( #1050 #1764 ).

This PR adds:

• handling of data_order with array (follow the order given by the array)
• new tooltip_order option that takes the same arguments as data_order (except for functions where parameters are values instead of data)
• tests that hopefully cover the majority of cases

This PR fixes:

• sort of tooltip if data_order is null or a function

[codecov-io]

Current coverage is 64.13% (diff: 100%)

Merging #1813 into dev will increase coverage by 0.39%

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[pchaganti]

+1

[bchartoff]

Would be great functionality, if a merge makes sense to y'all!

[phandel]

+1

[tcunha85]

+1

[jorgemmsilva]

+1

[aendra-rininsland]

Apologies for the delay in getting to this — merging!

[alexgerv]

@Aendrew this was merged onto dev. Should we open a new PR for master ?

[aendra-rininsland]

@alexgerv Yeah, if you wouldn't mind that would be terrific — apologies for the hassle!

[alexgerv]

No worries @Aendrew , see PR #2070

[chaitanmk]

Hi,

can you please provide sample code for tooltip_order.

[CaffeineFusion]

@chaitanmk - had a flick through the source and derived the following:

// Order by value
tooltip: {
	order: 'asc'
}

//Order by label
tooltip: {
    order: function (t1, t2) {
        return t1.id > t2.id;
    }
}

Note: The sorting for tooltips appears to work in reverse of the order functions for data labels.

data: {
    order: function (t1, t2) {
        return t1.id < t2.id;
    }
}

Corresponds to the opposite function for the tooltip sort:

tooltip: {
    order: function (t1, t2) {
        return t1.id > t2.id;
    }
}

[easz]

using [email protected]

so basically if I want the data shown in grouped tooltip having the same order as that in data columns, I have to extra declare this:

tooltip: {
    order: function(t1, t2) {
      return t1.index > t2.index;
    }

why we cannot just make it as default?