QTextEdit is slow in displaying huge paragraphs (>30000 lines per paragraph)

Loading a simple but big HTML file (2Mb and ~30000 lines) is slow, takes about 50 seconds on a fairly fast dual core AMD setup. Resizing the widget after it appears is also quite slow.

Note: The file in question loads everything into one single paragraph (with 30000 forced line breaks). A workaround is to create multiple paragraphs instead of displaying everything in one single paragraph with forced linebreaks.

This also appears to be slower in 4.2.x than in 4.1.x.