CKEditor - Real-time collaborative future-ready rich text editor
wxWidgets - wxWidgets: Cross-Platform GUI Library
Summernote - Summernote is a JavaScript library that helps users create WYSIWYG editors online.
GTK - GTK+ is a multi-platform toolkit for creating graphical user interfaces.
Froala Editor - Froala Editor is a WYSIWYG HTML editor that enables rich text editing capabilities for the applications.
Electron - Build cross platform desktop apps with web technologies