Font color is no longer auto adjusted with Angular 20

[dgerhardt]

👻 Brief Description

The text color is no longer auto adjusted, so components are no longer accessible when a dark background color is used.

🥞 Affected version

9.0.0 (Angular 20)

Reproduction

StackBlitz / reproduction repository link:

https://github.com/dgerhardt/angular-material-css-vars-ng-20-a11y

Steps to reproduce the behavior:

1. Create a new project using Angular 20
2. Set the primary color to #333333
3. Add a MatButton with primary color to a component
4. The text color of the button is black instead of white.

🚓 Expected behavior

The text color should auto adjust to ensure that there is always a high contrast. This was the case before Angular 20.

[json-derulo]

Thanks for reporting the issue. This is a side effect of #187 and affects multiple components, namely button, slide toggle, datepicker and progress bar.

It only happens if there is neither the dark theme selector nor the light theme selector set. This is also why in the demo everything appears normal. When opening the demo, switching to light theme and manually removing the isLightTheme class from the body element, the issue is also visible. Working on a fix right now.

[json-derulo]

Fixed with v9.0.1

[dgerhardt]

Thanks for the explanation and fixing this so quickly. 👍