The problem was that wmPushMatrix/wmOrtho/.. and similar functions did not work well for offscreen rendering. It would have been possible to make a fake subwindow for this, but I decided to just remove this extra layer as it does not seem to have much purpose and has been quite confusing when trying to fix other bugs. The relevant matrices are already stored in RegionView3D so there will be no increase in calls to glGetFloat, which may have been a performance reason to use this system in the past.