The default setting is AutoText, i.e. the label autodetects the format from text . If the format is RichText, the label uses the default mime source factory to resolve references to images. Note that a label is only useful for rather small documents with one or maximal two lines of text. If you need to display larger documents, a QTextView is the widget of choice. It will flicker less on resize and can also provide a scrollbar if necessary.
Possible choices are all blanks and linebreaks.
RichText - rich text rendering. The available styles are defined rendering style suits best, PlainText or RichText. AutoText - this is also the default. Reimplemented from QWidget. This may be either plain text or a small rich text document.