As mentioned above, the editor's text can be edited, i.e. the user can type text into the widget. This feature can be considered as a conveniently set up set of key bindings (e.g. the key `a' is bound to the function which inserts an `a' at the current cursor position). You can switch off the editing behaviour with the function disable from the class Configuration.html#Configuration.HasEnableHasEnable, but be warned: You can only change the text of enabled editors! Trying to insert text into a disabled editor is one of the most common Tk errors; it will not generate a run-time error but just silently fail to change the text of the editor, leaving the programmer in puzzled dismay.
The example htk/examples/simple/Maintexttag.hs shows what you can do with text tags, and how to use them. The module MarkupText from the toolkit allows a more abstract approach to displaying text with differents fonts, hyperreferences and so on (see Section 10 below).