bug(MatSelect): MatSelect in a CdkOverlay panel is not accessible to screen readers

[wildcardalice]

Is this a regression?

• Yes, this behavior used to work in the previous version

The previous version in which this bug was not present was

No response

Description

Using a screenreader to interact with a MatSelect dropdown inside an overlay panel prevents it from reading out the options

Reproduction

StackBlitz link: https://stackblitz.com/edit/bqqfav-gaxbdf
Steps to reproduce:

1. Active VoiceOver or other screen reader
2. Using a keyboard, click on the 'Launch dialog' button
3. Using a keyboard, navigate to the select and attempt to read the options

Expected Behavior

VoiceOver should read out the options, much like it does when interacting with the examples at https://material.angular.io/components/select/examples

Actual Behavior

VoiceOver does not read out the options. It only reads "expanded, completion selected". Pressing ctrl+option+space causes it to read "confirm Favorite pet, list box pop-up, Menu popup combobox".

Environment

• Angular: 17.2.0
• Browser(s): Google Chrome
• Operating System: macOS
• Screen reader: VoiceOver

[zarend]

Hello,

Thank you for reporting accessibility issues. I can reproduce.

• macos Sonoma 14.3.1 (23D60)
• chrome Version 122.0.6261.112 (Official Build) (arm64)
• test site: https://stackblitz.com/edit/bqqfav-gaxbdf

This appears to be a VoiceOver compatibility problem with aria-modal, but there is a work-around. By default, MatDialog with be an aria-modal with aria-modal="true". We set aria-modal to false using MatDialogConfig.

    this.dialog.open(DialogElementsExampleDialog, {
      ariaModal: false, // work-around VoiceOver compatibility issue with modal dialog (#28709)
    });

Stackblitz reproduction of work-around: https://stackblitz.com/edit/bqqfav-lnchne

Here's a bit more technical background of the problem.

What seems to happen is that VoiceOver isolates the content inside an aria-modal – that's all the DOM inside element with aria-modal="true". VoiceOver only has access to the modal and cannot see anything outside the modal. Overlay renders inside a <cdk-overlay-container/>, which is at the bottom of the DOM. it is not a child of MatDialog element. This causes compatibility issues with VoiceOver appeared to isolate Overlays from the content of the AriaModal. It caused the same behavior reported in this bug report and affected anything that uses Overlay, which is Angular component's popup system.

We worked around using aria-owns to creating a relationship in the DOM. That seemed to work for a little bit. Unfortunately, that work-around does not seem to work anymore. VoiceOver has known compatibility issues with aria-owns.

Assigning to myself with P2 priority.

Best Regards,

Zach