使用核心文本是否有UITextView和UITextField的开源重新实现？
Apple的SimpleTextInput有SimpleCoreTextView和EditableCoreTextView个类，明确说明：
File: SimpleCoreTextView.m
Abstract:
A view that draws text, reasons about layout, and manages a selection over its text range.
IMPORTANT: Its use of CoreText is naive and inefficient, it deals only with
left-to-right text layout, and it is by no means a good template for any text
editor. It is a toy implementation included only to illustrate how to bind
the system keyboard to some pre-existing text editor.
换句话说，它没有处理，例如阿拉伯语，效率低下。
根据Core Text和UITextInput协议系列，我们有什么替代方案可以完全实现可编辑的文本字段或文本视图？