Collection rendering performance improvements Part 1: Improve Entity actions render performance

[madsrasmussen]

Note

Requires the latest version of the UI Library with this PR merged: umbraco/Umbraco.UI#1129.
If testing without the latest UI Library version, the Entity Action popover will, in some cases, be positioned off-screen.

This PR makes sure that the Entity Actions list is only rendered when the popover is open.

Optimizations

• Begin observing the available Antity Action Manifests (used to display the first action) when the element enters the viewport.
• Create and render the Entity Action APIs only when the popover opens.

Poor man's performance stats from my computer:

Before the optimization, I started having trouble rendering a collection and selecting items when there were 100+ items. This also made the rest of the backoffice nearly unusable—I couldn’t navigate around properly.

After the entity action optimizations, I now only start seeing issues around 500–1000 items. I’ve been able to render a list with 2000 items (with a very long table render time), but I was still able to select items (with some delay) but afterwards navigating the rest of the backoffice fine.

Once we reach 500+ items, we’ll need to do a separate investigation into what’s causing the slow rendering of table items.

[Copilot]

Pull Request Overview

This PR improves the rendering performance of Entity Actions in collections by deferring the creation and rendering of associated action APIs until needed. Key changes include:

• Adding early-return guards in the document table column element to avoid rendering without required properties.
• Replacing the legacy popover implementation with a new umb-entity-actions-dropdown component in the workspace entity action menu.
• Introducing an IntersectionObserver in the entity actions bundle to delay observing entity actions until the element is in the viewport, along with new event types and refactored dropdown behaviors.

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
document-table-column-name.element.ts	Added guard checks for value.editPath and _name before rendering.
workspace-entity-action-menu.element.ts	Refactored component to use the new umb-entity-actions-dropdown element.
opened.event.ts & closed.event.ts	Introduced new events to mimic native toggle behavior.
index.ts (event)	Exported the new opened and closed events.
entity-actions-dropdown.element.ts	Added a new dropdown component that programmatically creates and caches its content on open.
entity-actions-bundle.element.ts	Integrated an IntersectionObserver for lazy initialization and replaced legacy dropdown usage.
dropdown.element.ts	Refactored open/close logic with a private open state and event dispatching.

Comments suppressed due to low confidence (2)

src/Umbraco.Web.UI.Client/src/packages/core/components/entity-actions-bundle/entity-actions-bundle.element.ts:41

• Consider disconnecting the IntersectionObserver in the element's disconnectedCallback to avoid potential memory leaks when the element is removed from the DOM.

		const observer = new IntersectionObserver(

src/Umbraco.Web.UI.Client/src/packages/core/components/dropdown/dropdown.element.ts:21

• [nitpick] Review the open property setter logic to ensure it does not conflict with the toggle event handler, preventing redundant calls to openDropdown or closeDropdown.

	public set open(value) {