Addition of TinyMCE to the Text Widget

In its first couple years, WordPress lacked rich/visual text editing. Before TinyMCE was incorporated in WordPress 2.0, users had to edit post content as raw HTML with some support from the Quicktags buttons. When widgets were introduced in WordPress 2.2, the Text widget was included which allowed a user to add content to their sidebar. Nevertheless, unlike the post editor, the Text widget did not incorporate TinyMCE, nor did it include Quicktags. For twelve years, since TinyMCE was added to core in 2005, users have had to hack around with HTML in their Text widgets to do things as simple as make text bold or add links. This has been featured even as recently as the 4.7 release video. Well, as of WordPress 4.8, the Text widget is finally getting the same treatment as the post editor with the introduction of TinyMCE for visual text editing, while still supporting raw HTML editing via a Text tab but now with the additional help of Quicktags: A primary reason for the long delay in incorporating TinyMCE into the Text widget was the difficulty of cleanly instantiating another copy of the WordPress visual editor dynamically after the page has loaded. Since WordPress 3.3 there has been the
Source: https://managewp.org/articles/15189/addition-of-tinymce-to-the-text-widget

source https://williechiu40.wordpress.com/2017/05/24/addition-of-tinymce-to-the-text-widget/