Show DialogFragment in full screen with status bar, change status bar background color and update status bar components color depending on background color to make them more readable

DialogFragment+FullscreenWithCustomStatusBarColor.kt

...
import androidx.fragment.app.DialogFragment
...
class MyDialogFragmentDialog : DialogFragment() {
    ...
    private val statusBarColorRes = R.color.colorPrimaryDark
    private var previousSystemUiVisibility: Int? = null
    ...
    override fun getTheme(): Int = R.style.FullscreenDialog
    ...
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        setupStatusBarColor()
    }
    ...
    override fun onDestroy() {
        previousSystemUiVisibility?.let(::setActivitySystemUiVisibility)
        super.onDestroy()
    }
    ...
    
    private fun setupStatusBarColor() {
        previousSystemUiVisibility = getActivitySystemUiVisibility()
        setStatusBarColor(statusBarColorRes)
    }
}

DialogFragmentExtensions.kt

val DialogFragment.window: Window? get() = dialog?.window
val DialogFragment.activityDecorView: View? get() = activity?.window?.decorView

fun DialogFragment.getActivitySystemUiVisibility(): Int? =
    window?.decorView?.systemUiVisibility

fun DialogFragment.setActivitySystemUiVisibility(flags: Int) {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
        activityDecorView?.systemUiVisibility = flags
    }
}

fun DialogFragment.setStatusBarColor(@ColorRes colorRes: Int) {
    window?.run {
        addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS)
        val color = ContextCompat.getColor(context, colorRes)
        statusBarColor = color

        // does not work if dim is enabled
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            val decorView = activityDecorView ?: return
            if (!color.isDark) {
                decorView.systemUiVisibility =
                    decorView.systemUiVisibility or SYSTEM_UI_FLAG_LIGHT_STATUS_BAR
            }
        }
    }
}

styles.xml

<style name="NoMarginsDialog" parent="Theme.AppCompat.Light.Dialog">
    <item name="android:windowBackground">@android:color/transparent</item>
    <item name="android:windowIsFloating">false</item>
    <item name="android:backgroundDimEnabled">false</item>
</style>

Where isDark come from?