android compose VisualTransformation

Android Compose provides a way to customize the appearance and behavior of UI components using the `VisualTransformation` API. `VisualTransformation` is a transformation that can be applied to a `TextField` or `EditText` component to modify the appearance of the text as it is being entered.

For example, you can use the `PasswordVisualTransformation` to mask the text entered in a password field with asterisks. You can also create your own custom `VisualTransformation` to achieve a specific behavior or appearance.

To apply a `VisualTransformation` to a `TextField` or `EditText` component, you can simply call the `visualTransformation` function and pass in the desired transformation.

Here's an example of using the `PasswordVisualTransformation`:

TextField(
    value = password,
    onValueChange = { password = it },
    label = { Text("Password") },
    visualTransformation = PasswordVisualTransformation()
)

And here's an example of creating a custom `VisualTransformation` to capitalize the text entered:

class CapitalizeTransformation : VisualTransformation {
    override fun filter(text: AnnotatedString): TransformedText {
        val uppercaseText = text.text.toUpperCase()
        return TransformedText(AnnotatedString(uppercaseText), OffsetMapping.Identity)
    }
}

TextField(
    value = name,
    onValueChange = { name = it },
    label = { Text("Name") },
    visualTransformation = CapitalizeTransformation()
)

In this example, the `CapitalizeTransformation` class implements the `VisualTransformation` interface and overrides the `filter` function to return a new `TransformedText` object with the text transformed to uppercase. The `OffsetMapping.Identity` parameter is used to maintain the original text position.

Overall, `VisualTransformation` provides a powerful way to customize the appearance and behavior of text fields in Android Compose.