https://bugs.winehq.org/show_bug.cgi?id=56045
--- Comment #7 from Esme Povirk madewokherd@gmail.com --- Yep, it's part of PresentationNative which is part of WPF that was never open-sourced. Someone would have to write a replacement (as was done for a few other parts), though changing the managed parts to not rely on it (as we did with System.Windows.Media.TextFormatting classes) can also work in some cases.