feat(graph): straight multiple edge. close #18424

[DendoD96]

Brief Information

This pull request is in the type of:

• bug fixing
• new feature
• others

What does this PR do?

Extend the possibility to support multiple edges betwen two node in graph using offset parameters.

Fixed issues

• [Feature] Multiple parallel edges #18424

Details

Before: What was the problem?

After: How does it behave after the fixing?

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

graph-offset.html
graph-multiple-edges-offset.html

Others

Merging options

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

Other information

[echarts-bot]

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Document changes are required in this PR. Please also make a PR to apache/echarts-doc for document changes and update the issue id in the PR description. When the doc PR is merged, the maintainers will remove the PR: awaiting doc label.

[Ovilia]

I tried with graph-multiple-edges-offset.html and it seems the multiple lines are not always visible when zooming. Is offset in pixels or what unit? If it's in pixel, then what if the width of all lines are larger than the size of the graph node size?

[DendoD96]

Hello @Ovilia, offset is a fixed value in pixel and when the width of all lines are larger than the size of the node graph edges are collapsed. This procedure take in consideration also the zoom level, so zomming in or out can cause the shrinking or the expansion of edges.

[Ovilia]

when the width of all lines are larger than the size of the node graph edges are collapsed

I think this behavior is quite unexpected to me when zooming. Can you explain why it should be like this?

[DendoD96]

Hello @Ovilia,
you are right, I had made some wrong considerations about rendering. Now I should have fixed the logic taking into account the zoom when applying the offset.