Improve focus behaviour in search

[krassowski]

References

Fixes #14308

Depends on codemirror/view@f49f2ee included in @codemirror/view 6.9.5, therefore required #14413

Code changes

• only create DOM event (i.e. focus) CM extension once, and only add it during editor setup phase
• support arbitrary nesting of highlight markers fixing current highlight not shown in some cases
• preserve current match when switching cells if possible
• if there is no current match, try to assign one
• do not ever set selection when searching in selection, instead just scroll to the match
• introduces (non-public) SearchStartAnchor type to disambiguate the search start behaviour allowing to fix highlighting issues
• introduces IHighlightAdjacentMatchOptions interface to specify whether highlighting should scroll/select new match
• do not scroll/select new match when starting search
  • this can be improved in follow-up: we could scroll/select if this is a new query (but not restart of query after document change)

User-facing changes

Extending selection after changing to command mode now works smoothly (does not revert to edit mode, which was caused by CodeMirror bug, and is faster - which was previously slowed down by needless cleaning of highlights due to both activeCellChanged and selectionCellChanged handlers being used - now the shared job will only be performed once).

Initial match is set consistently across various scenarios, e.g.:

Before	After

Including, in file editor, and when populating search box from selection (regardless of selection direction):

Backwards-incompatible changes

N/A

[jupyterlab-probot]

Thanks for making a pull request to jupyterlab!
To try out this branch on binder, follow this link:

[krassowski]

Merged master to clean update-links job failure that was addressed earlier.

[fcollonval]

Thanks a lot @krassowski for working on this.

[krassowski]

@andrii-i can we merge this one or did you have any specific feedback here?

[fcollonval]

Merging now to get it in the RC

[andrii-i]

@krassowski Good to merge, no feedback on my end, it was mentioned as needing a review last week but I have not came around to reviewing. Thanks for reviewing @fcollonval.