fix(core): skip updating focusPath state if unchanged

[bjoerge]

Description

As seen in the chart below, the commit that merged #6370 had severe impact on editor FPS.

The reason for this is that #6370 reverted an earlier PR that, among other things, skipped updating focusPath state in DocumentPaneProvider if the emitted focusPath was (deeply) equal to the current focus path. This, in combination with the portable text input emitting onFocus on selection change, which is emitted from the portable text editor on every keystroke, triggered excessive re-renders even in cases where the focus path did not really change.

This fixes the issue by skipping the state update if focus-path hasn't changed. Instead of taking the handed focusPath as-is, it gets it from the pool of existing focus paths, which returns a stable instance for equal paths.

Relevant benchmarks.

Note: body is the Portable Text array here. Higher is better

Before

After (higher is better)

What to review

Does the change make sense?

Testing

Should be covered by existing tests.

Notes for release

• Improved Portable Text editor performance

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Name	Status	Preview	Comments	Updated (UTC)
page-building-studio	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Sep 19, 2024 9:13am
performance-studio	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Sep 19, 2024 9:13am
test-compiled-studio	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Sep 19, 2024 9:13am
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test-studio	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Sep 19, 2024 9:13am

1 Skipped Deployment

Name	Status	Preview	Comments	Updated (UTC)
studio-workshop	⬜️ Ignored (Inspect)			Sep 19, 2024 9:13am

[github-actions]

No changes to documentation

[github-actions]

Component Testing Report Updated Sep 19, 2024 9:14 AM (UTC)

✅ All Tests Passed -- expand for details

File	Status	Duration	Passed	Skipped	Failed
comments/CommentInput.spec.tsx	✅ Passed (Inspect)	45s	15	0	0
formBuilder/ArrayInput.spec.tsx	✅ Passed (Inspect)	8s	3	0	0
formBuilder/inputs/PortableText/Annotations.spec.tsx	✅ Passed (Inspect)	31s	6	0	0
formBuilder/inputs/PortableText/copyPaste/CopyPaste.spec.tsx	✅ Passed (Inspect)	36s	11	7	0
formBuilder/inputs/PortableText/copyPaste/CopyPasteFields.spec.tsx	✅ Passed (Inspect)	0s	0	12	0
formBuilder/inputs/PortableText/Decorators.spec.tsx	✅ Passed (Inspect)	17s	6	0	0
formBuilder/inputs/PortableText/DisableFocusAndUnset.spec.tsx	✅ Passed (Inspect)	10s	3	0	0
formBuilder/inputs/PortableText/DragAndDrop.spec.tsx	✅ Passed (Inspect)	3m 0s	0	0	0
formBuilder/inputs/PortableText/FocusTracking.spec.tsx	✅ Passed (Inspect)	45s	15	0	0
formBuilder/inputs/PortableText/Input.spec.tsx	✅ Passed (Inspect)	1m 45s	21	0	0
formBuilder/inputs/PortableText/ObjectBlock.spec.tsx	✅ Passed (Inspect)	1m 15s	18	0	0
formBuilder/inputs/PortableText/PresenceCursors.spec.tsx	✅ Passed (Inspect)	8s	3	9	0
formBuilder/inputs/PortableText/RangeDecoration.spec.tsx	✅ Passed (Inspect)	26s	9	0	0
formBuilder/inputs/PortableText/Styles.spec.tsx	✅ Passed (Inspect)	18s	6	0	0
formBuilder/inputs/PortableText/Toolbar.spec.tsx	✅ Passed (Inspect)	36s	12	0	0
formBuilder/tree-editing/TreeEditing.spec.tsx	✅ Passed (Inspect)	0s	0	3	0
formBuilder/tree-editing/TreeEditingNestedObjects.spec.tsx	✅ Passed (Inspect)	0s	0	3	0

[juice49]

Looks great!