Angular Material 15: How to customize the styling of buttons and input fields?

I would like to override the font width in Angular Material 15 buttons and input fields.

Material docs say here that I should do this in my stylesheet:

@use '@angular/material' as mat;

$my-custom-level: mat.define-typography-level(
  $font-family: Roboto,
  $font-weight: 400,
  $font-size: 1rem,
  $line-height: 1,
  $letter-spacing: normal,
);

I don't think this code actually "applies" my font changes, I guess it needs to be applied to the current theme or something, I tried various things but couldn't figure out how to apply this. Any hints would be appreciated.

I tried to create my custom theme but couldn't figure out where to apply $my-custom-level:

$config: mat.define-typography-config();

$theme: mat.define-light-theme((                                                    
    typography: $config,
));

@include mat.input-typography($theme);

It took me quite some time to get to a solution of your problem: Styling the buttons less complicated since $button is a default property in typography-config. Yet for the input-fields I needed to create a custom-property in typography-config and then manually assign it via @mixin to the class-selector of the material-input-fields (.mat-mdc-form-field).

@use '@angular/material' as mat;
@use "sass:map";

/* Styles to be applied to buttons */
$my-custom-button: mat.define-typography-level(
  $font-family: 'Roboto',
  $font-weight: 500,
  $font-size: 2rem,
  $line-height: 1,
  $letter-spacing: 'normal'
);

/* Styles to be applied to input-fields */
$my-custom-input: mat.define-typography-level(
  $font-family: 'Roboto',
  $font-weight: 400,
  $font-size: 1rem,
  $line-height: 1,
  $letter-spacing: 'normal'
);

/* Merge custom configs into existing config */
$my-typography-config: map.merge(
    mat.define-typography-config(
        /* 'button'-property will work out of the box */
        $button: $my-custom-button
    ),
    (
        /* 'input'-property will have to be assigned under '@mixin typography' further below */
        'input': $my-custom-input
    )
);

/* Apply custom config */
@include mat.all-component-typographies($my-typography-config);

/* Let's assign the custom property 'input' that we defined above */
@mixin typography($theme) {
    $custom-typography-config: mat.get-typography-config($theme);
    
    .mat-mdc-form-field {
        @include mat.typography-level($custom-typography-config, 'input')
    }
}

/* Define custom app-theme based on custom-configs */
$app-theme: mat.define-light-theme(
    (
        typography: $my-typography-config,
    )
);

/* Apply custom app-theme */
@include typography($app-theme);