LayoutObserver.kt

    private class LayoutObserver(private val view: View, private val callback: (Size) -> Unit) : ViewTreeObserver.OnGlobalLayoutListener {

        init {
            if (!view.viewTreeObserver.isAlive)
                throw IllegalArgumentException("Go fuck yourself")
            
            view.viewTreeObserver.addOnGlobalLayoutListener(this)
        }
        
        override fun onGlobalLayout() {
            view.viewTreeObserver.removeOnGlobalLayoutListener(this)
            callback(Size(view.width, view.height))
        }
    }