bug(MatFormField): Outline form field with prefix labels misalign when the document direction is changed.

[AldoJV]

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

When the direction property on the document is changed (LTR to RTL and viceversa), outline form fields with a prefix suffer from label misalignment. This presents a problem for apps that have forms and need to support a location switcher that has a RTL language like Arabic.

Reproduction

StackBlitz link: https://stackblitz.com/edit/3rswucyt?file=src%2Fexample%2Fform-field-appearance-example.html
Steps to reproduce:

1. Observe button in default LTR mode.

3. Click the "Toggle dir" button to change the direction in the wrapper to RTL
4. Observe the label is now misaligned, trailing off to the right.

5. Click the "Rerender" button to remove the form from the dom for one second
6. Observe that when the component re-renders, the label alignment is correct.

7. Click the "Toggle dir" button again to set the direction back to LTR
8. Observe the label is misaligned again, only fixes when re-rendering the button.

Expected Behavior

When changing the direction, the label alignment should react and adjust.

Actual Behavior

The label is not aligning, it seems that it has the calculation obtained from before the direction changed. Since re-rendering the component fixes the problem, it appears that the logic is inside the component, but there is no way to notify the component a re-calculation is needed.

Environment

• Angular: 22.1.0
• CDK/Material: 22.1.0
• Browser(s): Google Chrome, Microsoft Edge, Safari
• Operating System (e.g. Windows, macOS, Ubuntu): MacOS