fix(bar): fix wrong label position when bar width/height is 0

[Justin-ZS]

Brief Information

This pull request is in the type of:

• bug fixing
• new feature
• others

What does this PR do?

Fix incorrect data label position when bar width/height is 0.

Fixed issues

• [Bug] if the value is 0, data label is rendered under the axis line when postion is "outside" #21144

Details

Before: What was the problem?

When a bar has zero width or height (data value is 0), the label position calculation for label.position: 'outside' was incorrect, especially when the axis is inverted.
The original logic only checked layout.height >= 0 or layout.width >= 0 without considering axis inversion, causing labels to appear in wrong positions.

After: How does it behave after the fixing?

Added two helper functions getLabelPositionForHorizontal and getLabelPositionForVertical to properly handle label positioning when bar dimensions are zero.
The functions check the value axis's inverse property to determine the correct label position, ensuring labels appear correctly regardless of axis configuration.

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

ZRender Changes

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

Related test cases or examples to use the new APIs

N.A.

Others

Merging options

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

Other information

Modified src/chart/bar/BarView.ts to replace simple ternary operators with smarter function calls that consider axis inversion when determining label positions for zero-dimension bars.

[echarts-bot]

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[Ovilia]

Does this also depends on label.position?

[Justin-ZS]

Does this also depends on label.position?

Yes. the calculated value is assigned to labelPositionOutside and is only used for position: 'outside'

[github-actions]

The changes brought by this PR can be previewed at: https://echarts.apache.org/examples/editor?version=PR-21218@cbf5c62

[echarts-bot]

Congratulations! Your PR has been merged. Thanks for your contribution! 👍

[Ovilia]

Thanks for your contribution!