refactor: [POC] investigate replacement of mxGraph by [email protected] (2nd attempt)

[tbouffard]

This is a POC and it is not intended to be merged into master, so don't expect to find a high quality code here! 😺
This is a continuation of #2366

Please don't rebase on master. If necessary, merge the master branch but instead we will create a new POC with the latest changes from the master branch.

Start from master e8fa907 (0.37.0 with dev dependencies update only)

Purpose

• evaluate the migration effort
• detect problems early
• apply improvements to the master branch to ease the future migration and improve tests
• provide feedback to the maxGraph community and if possible fixes that we integrated in this PR as workaround
• be ready to easily reuse this effort in a new Pull Request to test new maxGraph releases

Status

This POC is completed.

• rebase previous POC on master branch e8fa907 (post 0.37.0 version)
• source compile
• dev server starts, the demo is usable
  • label position OK (wasn't working in the previous POC), navigation and theme switch OK (see video below)
  • elements-identification demo works. It uses overlays, CSS and Style update (see video below)
• ✔️ unit tests pass 💪🏿
• ✔️ integration tests 🎉
• ❌ e2e tests: they detect real issues.
  • Some BPMN rendering tests fails as in the previous POC due to issues in maxGraph 0.1.0 which are fixed in later versions.
    • message flow icon not correctly positioned
    • edge marker are not filled
  • To investigate
    • edge: the arcSize seems larger than with mxGraph
    • association and message flow dashed: the dashed positions are not exactly in the same order as with mxGraph
  • apparently work (currently failed because of existing issues described above)
    • overlays
    • fit/zoom
    • pan
    • theme
• ❌ SVG export KO as in the previous POC. No work done on this topic
• Remaining tasks associated to the migration are marked in the code as // TODO [email protected]. Most tasks are related to changes to do with newer versions of maxGraph

Demo: navigation, theme and label position

See #2756 (comment)

PR_2756_2nd_poc_maxgraph-0.1.0_fc95b24_navigation_theme_ok.mp4

Demo: Overlays, CSS and Style Update API

PR_2756_2nd_poc_maxgraph-0.1.0_c17cb046_elements-identification_OK.mp4

Improvements ported to the master branch

• refactor: remove mx prefix in variables related to mxGraph objects #2834
• test: add more tests for StyleComputer #2835
• fix!: generate correct CSS class name for adhoc subprocess #3058

Detected maxGraph issues

• model.setCellStyle: require to pass a clone of the current style. Otherwise, the Style is not updated. See Graph.setCellStyles may not propagate style changes maxGraph/maxGraph#326
• styleUtils.setStyleFlag set the value to 0 when the original value for the key is undefined. See fix: correctly set the flag value in setStyleFlag maxGraph/maxGraph#377
• fix: correctly compute the style when setting undefined/none maxGraph/maxGraph#383

Remaining tasks

Handle TODO in the code

Preview Give feedback

1. manage the "TODO rebase" in the code. Created while rebasing the previous code on the master branch
2. review all "TODO [email protected]": some can be handled thanks to the fix done on the master branch and that weren't available in the previous POC
3. the extraCssClasses should be a property in the CellStyle and not defined with a deep nested object

CSS classes not applied with the API

Preview Give feedback

1. in the elements-identifications.html demo, the CSS are sometimes applied but seems to disappear during navigation
2. integration tests fail: the CSS classes are in the maxGraph model, but they are not generated in the DOM

Update Style API: make it work

Preview Give feedback

1. font style value is incorrect. Is is lower by one. Use workaround to fix the problem (seems to be an issue in maxGraph)
2. passing default value work
3. update and reset work

Rework the tests

Preview Give feedback

1. Make the tests pass
2. Provide a status of the e2e tests.

[tbouffard]

POC completed, I am going to create a new poc based on the same commit on the master branch and maxGraph v0.10.0 to validate that this new version of maxGraph provides most improvements we need.