GTK+ 3 Reference Manual
Multiline Text Editor
Text Widget Overview
— Overview of GtkTextBuffer, GtkTextView, and friends
GtkTextIter
— Text buffer iterator
GtkTextMark
GtkTextBuffer
GtkTextTag
— A tag that can be applied to text in a GtkTextBuffer
GtkTextTagTable
— Collection of tags that can be used together
GtkTextView
— Widget that displays a GtkTextBuffer