Run attached example and see what Creator Application Output View log outputs. Then compare to application widget output. In Qt 5.2.1 strings are correctly similar but from Qt 5.3.0 it's different and invalid.
Originally string is compared to Mac Text editor result (test by open application sample.txt) which shows correct font for each letter. But font like "Telugu MN" or "Menlo" should show correct result in Qt also.
Change that cause regression from Qt 5.2.1 is the change of harfbuzz implementation: https://qt.gitorious.org/qt/odysseus-qtbase/commit/2d576f79f748ca4c9bb54634f0fd44fa207a2248