BasicTextAdornment for paragraph or selected text range single or multiline

Nothing wrong with multiple style ranges. Text adornments are output produced by the composer for storage within wax (rendered text). Consider them as objectized chance to draw, what you draw is up to you. In preparation (your factory code within the attribute) you can look around your actual composed text, consider the environment (left side, right side, within, also be prepared to encounter multiple chunks / bindings of your own data lumped into a single range, or even overlaps after inconsistent edits) and remember to draw accordingly - store the resulting information in an additional data object of the adornment. For example kTextAdornmentUnderlineBoss would store all data from underline related attributes as seen in the composition state, producing a kTextAdornmentUnderlineDataBoss . That "look around" process would depend on additional objects that is not demonstrated by the BTA example (e.g. hyperlink text source). Handling text adornment data at line wraps, or even across pages, was also left as exercise.

Note that the BTA example is very old, it predates the CS5 split between UI and model plug-in by roughly a decade. Nowadays the IgnoreTag in the .fr is a bad hack. For real world use move most of the plug-in into a model plug-in and only keep the action component in the UI.

Note also that the XML subsystem does not use text adornments, it uses a (page item) adornment and a draw event. I did not look which of them draws the brackets.