Fix/axis pointer multi

[100pah]

fix:
(1) Fix that tooltip shows multiple values around both sides of the pointer. Fix #9829.
(2) Fix a probably typo (diff < maxDistance) introduced by 4ef66e1
(3) Remove the previous logic that resolved #2869. Because currently if there are multiple values on the same axis tick, both of them will be found and displayed in tooltip by default. The related historical commits:
60d341f (fix #2869)
3426bd0 (support find multiple values on the same axis tick).

[pissang]

Does this mean we SHOULD NOT get more than one item in this method?

[100pah]

No. If there are more than one items on a axis ticks, we get more than one items.
If itemN --- pointer ---- itemN+1 we got only itemN, but not both itemN and itemN+1.
But the comment need to be updated to make it more understandable.

[pissang]

Perhaps it's more clear to use push instead of a self-increase index here.

[100pah]

Just a little optimize to avoid always do arr.length = 0; arr.push(i).
I think it's OK since many self managed length is used in ArrayBuffer in this file ?

[pissang]

Understand, didn't see the nearestIndicesLen will be reset to 0 in line https://github.com/apache/incubator-echarts/blob/2eac3913216f4f9a462897a0da839a878d438dea/src/data/List.js#L1178

[pissang]

Is this same to (dist === minDist && diff !== minDiff) because diff is dist with sign

[100pah]

Only when the current minDiff < 0 and diff >= 0 we clear the previous records.
That means that we choose diff >= 0 with higher priority than diff <= 0.

[pissang]

I'm confused about this condition. diff should be always same with minDiff if https://github.com/apache/incubator-echarts/blob/2eac3913216f4f9a462897a0da839a878d438dea/src/data/List.js#L1177 is executed.

[100pah]

The previous condition

 if (dist < minDist
                || (dist === minDist && diff >= 0 && minDiff < 0) { ... }

is not always entered, as the previous comment described.

[pissang]

Can we get the following rule from these codes:

If the condition

dist < minDist || (dist === minDist && diff >= 0 && minDiff < 0)

is failed.

Then

1. dist < minDist
   => Math.abs(diff) !== Math.abs(minDiff)
   => diff !== minDiff
2. Or diff >= 0 && minDiff < 0
   => diff !== minDiff

Which means the diff === minDiff condition will always be failed.

[100pah]

minDiff and minDist will be modified if dist < minDist || (dist === minDist && diff >= 0 && minDiff < 0) is true.

Take this test case for example:

function core({diff, minDiff}) {
    console.log('---- minDiff:', minDiff, 'diff:', diff);
    var dist = Math.abs(diff);
    var minDist = Math.abs(minDiff);

    if (dist < minDist
        || (dist === minDist && diff >= 0 && minDiff < 0)
    ) {
        minDist = dist;
        minDiff = diff;
        nearestIndicesLen = 0;
        console.log('Clear previous');
    }
    if (diff === minDiff) {
        console.log('Add index');
    }
    else {
        console.log('Not add index');
    }
}


core({minDiff: 5, diff: -5})
core({minDiff: 5, diff: 5})
core({minDiff: -5, diff: 5})
core({minDiff: -5, diff: -5})
core({minDiff: 5, diff: 4})
core({minDiff: -5, diff: -4})
core({minDiff: 5, diff: 6})
core({minDiff: -5, diff: -6})

The result is:

---- minDiff: 5 diff: -5
 Not add index
---- minDiff: 5 diff: 5
 Add index
---- minDiff: -5 diff: 5
 Clear previous
 Add index
---- minDiff: -5 diff: -5
 Add index
---- minDiff: 5 diff: 4
 Clear previous
 Add index
---- minDiff: -5 diff: -4
 Clear previous
 Add index
---- minDiff: 5 diff: 6
 Not add index
---- minDiff: -5 diff: -6
 Not add index