fix(dataZoom): avoid NaN in single-point shadow. close #21649

[rahul37wallst-sudo]

Brief Information

This pull request is in the type of:

• bug fixing
• new feature
• others

What does this PR do?

Fixes slider dataZoom data shadow rendering for single-point time-axis series by avoiding NaN shadow coordinates.

Fixed issues

• [Bug] Regression in 6.x: dataZoom slider showDataShadow renders nothing when the shadow-source series has a single data point on a time axis (NaN from zero-width extent) #21649: dataZoom slider showDataShadow renders nothing when the shadow-source series has a single data point on a time axis.

Details

Before: What was the problem?

For slider dataZoom with showDataShadow: true on a time axis, a single-point shadow-source series produced a zero-width data extent.

That made the time-axis shadow coordinate normalization divide by zero:

size[0] / (thisDataExtent[1] - thisDataExtent[0])

The resulting Infinity could then produce NaN shadow coordinates, causing the slider data shadow to disappear.

After: How does it behave after the fixing?

The time-axis proportional coordinate path is now used only when the data extent span is positive and finite.

For single-point time-axis data, the slider data shadow falls back to the existing step-based coordinate path, keeping polygon/polyline points finite and allowing the shadow to render.

A regression test was added for a single-point time-axis slider dataZoom case.

Document Info

One of the following should be checked.

• This PR doesn't relate to document changes
• The document should be updated later
• The document changes have been made in apache/echarts-doc#xxx

Misc

Security Checking

• This PR uses security-sensitive Web APIs.

ZRender Changes

• This PR depends on ZRender changes (ecomfe/zrender#xxx).

Related test cases or examples to use the new APIs

Added unit regression test:

• test/ut/spec/component/dataZoom/SliderZoomView.test.ts

Validation run:

• npx jest --config test/ut/jest.config.cjs --coverage=false test/ut/spec/component/dataZoom/SliderZoomView.test.ts --runInBand
• npx eslint src/component/dataZoom/SliderZoomView.ts test/ut/spec/component/dataZoom/SliderZoomView.test.ts
• git --no-pager diff --check
• npm run checktype

Merging options

• Please squash the commits into a single one when merging.

Other information

[echarts-bot]

Thanks for your contribution!
The community will review it ASAP. In the meanwhile, please checkout the coding standard and Wiki about How to make a pull request.

Please DO NOT commit the files in dist, i18n, and ssr/client/dist folders in a non-release pull request. These folders are for release use only.