refactor: use shadow root SlotObserver to update breadcrumbs items#11784
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Replace `ItemsSlotController` and its per-item `MutationObserver` with a single `SlotObserver` targeting the shadow root plus a subtree `MutationObserver` for `path` attribute changes. The shadow-root-level observer prepares for the upcoming overflow feature: its union diff naturally suppresses callbacks for cross-slot reassignment between `root`, default, and `overlay` slots, so the overflow logic won't loop back through the observer. `flush()` runs the first pass synchronously so the `current` state on the last item is applied during `firstUpdated()`. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
web-padawan
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vursen
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May 20, 2026
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This ticket/PR has been released with Vaadin 25.2.0-beta1. |
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Replace
ItemsSlotControllerand its per-itemMutationObserverwitha single
SlotObservertargeting the shadow root plus a subtreeMutationObserverforpathattribute changes.The shadow-root-level observer is what the upcoming overflow PR needs:
its union diff naturally suppresses callbacks for cross-slot
reassignment between
root, default, andoverlayslots, so theoverflow logic won't loop back through the observer. Landing the
refactor on its own keeps the overflow PR focused on the new feature.
flush()runs the first pass synchronously so thecurrentstate onthe last item is applied during
firstUpdated().Part of #11770
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