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fix(axis-log): Enable ticks under 1e-10, fixes #21099 #21107

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Ovilia merged 2 commits into from
Jul 17, 2025
+67 −2
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fix(axis-log): Enable ticks under 1e-10, fixes #21099 #21107

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fix(axis-log): enable ticks under 1e-10, fixes #21099
SihongShen Jul 16, 2025
d521d53
fix(axis-log): replace function, add examples to logScale.html
SihongShen Jul 17, 2025
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8 changes: 6 additions & 2 deletions src/scale/Log.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -64,9 +64,13 @@ class LogScale extends IntervalScale {

return zrUtil.map(ticks, function (tick) {
const val = tick.value;
let powVal = fixRound(mathPow(base, val));
const rawVal = mathPow(base, val);
let roundingCriterion = null;

// Fix #21099
const precision = numberUtil.getPrecisionSafe(rawVal) || 0;
let powVal = parseFloat(fixRound(rawVal, precision as number, true));
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@100pah 100pah Jul 19, 2025 •
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@SihongShen @Ovilia I don't fully understand the purpose of this handling.

If rawVal has the fractional part digits <= 20, rawVal will be equal to powVal, nothing changes.
Otherwise, if the fractional part digits > 20, the number.round method internally clamp it to 20, but that doesn't make sense in this scenario and may lead incorrect results, e.g, (1e-40).toFixed(20) we get 0.

image

From my understanding, the "fix round" applied in src/scale is meant to correct rounding errors introduced by floating-point computation, (such as the well-known case where 0.1 + 0.2 === 0.30000000000000004, when representing and calculating decimal fractional number in binary).

But Math.pow(base, tick.value) shouldn't suffer from such kind of rounding error, because the Log.ts guarantees interval and tick.value to be integers, and the base is typically an integer as well. They can be exactly represented in ieee754 64-bit floating-point number (assume no overflow - this is an separate topic).

Therefore, there is no opportunity for rounding errors to be accumulated beyond Number.EPSILON * Math.pow(2, ieee754_double_exponent(tick.value)) and result in a different result when converted back to a decimal string.
(Correct me if I'me wrong.)

Therefore, I think we should just remove this precision and rounding handling here. Just be:

let powVal = mathPow(base, val);

I tried to fix it in #21120


// Fix #4158
if (val === extent[0] && this._fixMin) {
roundingCriterion = originalExtent[0];
Expand Down Expand Up @@ -202,7 +206,7 @@ class LogScale extends IntervalScale {
if (!scaleBreakHelper) {
return;
}
const {parsedOriginal, parsedLogged} = scaleBreakHelper.logarithmicParseBreaksFromOption(
const { parsedOriginal, parsedLogged } = scaleBreakHelper.logarithmicParseBreaksFromOption(
breakOptionList,
this.base,
zrUtil.bind(this.parse, this)
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61 changes: 61 additions & 0 deletions test/logScale.html
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