Improve force layout with fixed positions

[flo-dup]

Please check if the PR fulfills these requirements

• [x] The commit message follows our guidelines
• [ ] Tests for the changes have been added (for bug fixes / features)
• [x] Docs have been added / updated (for bug fixes / features)

Does this PR already have an issue describing the problem? No

What kind of change does this PR introduce? Feature

What is the current behavior? When only a few positions are not fixed, force layout is

• too slow
• putting all non-fixed nodes in the middle of the diagram, leading to a messy spiderweb there

What is the new behavior (if this is a feature change)? Force layout is now fast when only a few positions are not fixed, and the non-fixed nodes are better placed.

Does this PR introduce a breaking change or deprecate an API?

• [ ] Yes
• [x] No

Other information: the non-fixed position suffered

• repulsion forces from all the nodes, leading to a n^2 complexity
• attraction force to the center, which was packing all the non-fixed nodes in the middle of the diagram

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
96.8% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud