Comment 2 for bug 1451778

Using QFileInfo::canonicalFilePath() is basically correct, but some post-processing is needed. The prefix of the canonical file path has to be matched against the canonical file path of the configured music directories. If a match is found it has to be replaced by QFileInfo::absoluteFilePath() of that specific music directory which might contain a symbolic link.

Note: Music directories must be referenced by their absolute file path! Their canonical file path may vary, i.e. if the target directory of a symbolic link is changed in the file system.

Precondition: The canonical file paths of all music directories must be disjunct, i.e. none is the prefix of any other. This restriction should be checked not only when adding new music directories, but also on every startup of Mixxx! The canonical file paths may vary even while Mixxx is running, but that is definitely out of scope.