A structural directive that marks the ng-template to be used as the popup for a combobox. This content is conditionally rendered.

The content of the popup can be a ngListbox, ngTree, or role="dialog", allowing for flexible and complex combobox implementations. The consumer is responsible for implementing the filtering logic based on the ngComboboxInput's value.

<ng-template ngComboboxPopupContainer>
  <div ngListbox [(value)]="selectedValue">
    <!-- ... options ... -->
  </div>
</ng-template>

When using CdkOverlay, this directive can be replaced by cdkConnectedOverlay.

<ng-template
    [cdkConnectedOverlay]="{origin: inputElement, usePopover: 'inline' matchWidth: true}"
    [cdkConnectedOverlayOpen]="combobox.expanded()">
  <div ngListbox [(value)]="selectedValue">
    <!-- ... options ... -->
  </div>
</ng-template>