feat(ui5-toolbar-item): add shrink-content property

[NakataCode]

Problem

When a ui5-toolbar-item with overflow-priority="NeverOverflow" contains wide content (e.g. a ui5-title with long text), it pushes other items — including the overflow button — completely out of view. This is because all toolbar item wrappers have flex-shrink: 0, so nothing yields space.

The spec clarifies that the toolbar has no built-in mechanism for long content in small viewports, and NeverOverflow only guarantees the item won't go to the popover — it makes no promise about layout when the item exceeds the container width. Titles are also intended to be short control-group labels per the Fiori spec, so automatic shrinking behavior would be surprising and could break existing layouts.

Solution

Add an opt-in shrink-content boolean property to ui5-toolbar-item. When set, the item's wrapper receives the existing .ui5-tb-self-overflow CSS class (flex-shrink: 1; flex-grow: 1; min-width: 2.5rem), allowing it to yield space to other items instead of pushing them out.

Implementation details

• shrinkContent property on ToolbarItem — opt-in, default false
• hasOverflow getter returns true when shrinkContent is set, hooking into the existing self-overflow CSS path with no new CSS required
• clampMaxWidth getter added to ToolbarItemBase (returns true by default, following the existing behavioral flag pattern of hasOverflow, isSeparator, ignoreSpace etc.). Overridden in ToolbarItem to return !this.shrinkContent, preventing the max-width capping logic in addItemsAdditionalProperties from permanently freezing the item at its first-render width
• shrinkContent items excluded from minWidth accumulation in storeItemsWidth — their rendered width is flex-distributed, not a stable natural width

Usage

<ui5-toolbar align-content="Start">
    <ui5-toolbar-item overflow-priority="NeverOverflow" shrink-content>
        <ui5-title wrapping-type="None">Long title that should yield space...</ui5-title>
    </ui5-toolbar-item>
    <ui5-toolbar-button text="Edit"></ui5-toolbar-button>
</ui5-toolbar>

Fixes: #13768

[sap-ui5-webcomponents-release]

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[github-actions]

👋 Heads-up: dev close is in effect

Thanks for the contribution! This repository is currently in dev close ahead of release 2.26 (scheduled 2026-08-26, UTC). See the release schedule for the full timeline.

This PR appears to introduce public-API changes (detected by diffing the Custom Elements Manifest against the latest published version on npm):

@ui5/webcomponents

• ➕ added interface: IToolbarItemContent
• ➕ added property: shrinkContent
• ➕ added attribute: shrink-content

Could you please hold off on merging into main until the release ships? Public-API changes are best landed in the next dev cycle so they don't slip into the release at the last minute. Once the release is out, this PR is good to go.

If this change must ship in the current release, please request a review from one or two members of @UI5/ui5-team-webc so the team can sign off explicitly.

💬 False positive? If you believe this PR doesn't actually change the public API (e.g. only internal refactoring, or an entry the detector mis-attributed), please reply on this thread — your feedback helps us improve the detection during this trial run.

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