The Q3FileIconProvider class provides icons for Q3FileDialog to use.
By default Q3FileIconProvider is not used, but any application or library can subclass it, reimplement pixmap() to return a suitable icon, and make all Q3FileDialog objects use it by calling the static function Q3FileDialog::setIconProvider().
It is advisable to make all the icons that Q3FileIconProvider returns be the same size or at least the same width. This makes the list view look much better.
If pixmap() returns 0, Q3FileDialog draws the default pixmap.