Custom tooltip doesn't receive all data when dataset is hidden

[life-of-e]

I've got a custom HTML tooltip working just fine when all my datasets are enabled/shown. However, if I hide a dataset by clicking on the legend, the tooltip code isn't given all of the possible datasets.

AssumeI have six datasets on a chart with these labels/names:
Line1, Line2, Line3, Line4, Line5, Line6

Also assume that I've instrumented the tooltip label callback with a console.log() to print out the dataset label.

When hovering over the chart and all datasets are enabled, the console shows me the six dataset labels:
Line1
Line2
Line3
Line4
Line5
Line6

Now hide dataset Line3 by clicking on its name in the legend. The legend shows the name with a strikethrough font and the line on the chart disappears. Hover over the chart again and this appears in the console:
Line1
Line2
Line3
Line4
Line5

It skips Line6. Now hide another dataset, for example Line2, and you get this:
Line1
Line2
Line3
Line4

So instead of iterating over all the lines it's apparently counting how many are visible and iterating over only that many.

There are some other oddities, too, like hiding only Line4 will result in four entries. There's nothing special in my tooltip code, it processes everything that is handed to it and I don't have any other customizations so I'm not sure where the data is stopping.

Where do I go in the code to fix this problem?

[life-of-e]

I was wrong sort of. It does fix how the data is sent to the tooltip but it doesn't hide the line graph itself. So I'm still in search of where this problem should be fixed so that the tooltip receives the right set of data.

Original reply:
So I found out where it's happening. In the main Chart class there is the function _getSortedDatasetMetas(filterVisible)

the if (!filterVisible || meta.visible) trips up as soon as you hide datasets and doesn't push all the sets. I took out the if statement and just let the push execute for all items. Then I just filter for the hidden property within the code generating the tooltip.

Is there a place in the configuration where I can set filterVisible to true instead of editing the code?

_getSortedDatasetMetas(filterVisible) {
const me = this;
const metasets = me._sortedMetasets;
const result = [];
let i, ilen;
for (i = 0, ilen = metasets.length; i < ilen; ++i) {
const meta = metasets[i];
if (!filterVisible || meta.visible) {
result.push(meta);
}
}
return result;
}

[kurkle]

I'd suspect your tooltip generating code to use wrong index to determine which datasets are visible. But without a reproduce thst is all I'm going to do.

[life-of-e]

So in the simplest case I have a label callback to format the label and then the tooltip itself. The label callback is getting a context for each item in the chart but I don't get them all.

I tested by making a very simple label callback that just prints the context to the console and assigned this to Chart.defaults.plugins.tooltip.callbacks.label

function label_callback(context)
{
console.log(context.datasetIndex + ' ' + context.dataset.label);
}

I get this when everything is visible (I have six total line plots):
22:47:51.784 0 Line Voltage
22:47:51.784 1 Line Voltage Peak
22:47:51.784 2 Line Voltage Valley
22:47:51.784 3 Line Frequency
22:47:51.784 4 Line Frequency Peak
22:47:51.785 5 Line Frequency Valley

Now if I hide Line Frequency (index 3) I get this:
22:49:19.544 0 Line Voltage
22:49:19.545 1 Line Voltage Peak
22:49:19.545 2 Line Voltage Valley
22:49:19.545 3 Line Frequency
22:49:19.545 4 Line Frequency Peak

If I hide Line Frequency Valley (index 5) in addition to the above (two plots hidden), I get this:
22:50:37.711 0 Line Voltage
22:50:37.712 1 Line Voltage Peak
22:50:37.712 2 Line Voltage Valley
22:50:37.712 3 Line Frequency

So is it sending me the wrong contexts for the labels?

[life-of-e]

I also just disabled my custom tooltips and the default ones still have the same problem

[life-of-e]

Ok, to reproduce the problem, create a chart of multiple lines (N) and then add a very simple tooltip label callback:
function label_callback (context)
{
console.log(context.datasetIndex);
return '';
}

And assign to the tooltip (I did it as a default):
Chart.defaults.plugins.tooltip.callbacks.label = label_callback

This will generate a blank tooltip when hovering but the console will show the numbers 0 through N-1 for the total number of lines. Now hide one line by clicking the legend and try again. The output will be the numbers 0 through N-2 with values unrelated to the datasets themselves.

[kurkle]

Ok, I don't see any obvious errors there either, though.

[life-of-e]

Which version of cjart.js is the code pen using?

[kurkle]

Chart.version
21:03:32.357 "3.5.1"

[life-of-e]

I wonder if that's the difference since I'm using 3.3.2

[life-of-e]

Found it, it was a typo I made when transcribing your interpolation code.