This effort is about reorganizing WineD3D and making sure backend functions are quarantined to their own files. The hoped for end result is to avoid large header files that aren't needed for all backends, help discover functions incorrectly tied to back-ends, help find more code that could be made local to a backend, and better logically separating the WineD3D code.
The first merge request is about moving Vulkan declarations to their own wined3d_vk.h header file. At least two more merge requests are expected as part of this code reorganization.
Hopefully in the end this will allow for a cleaner WineD3D codebase and hopefully discovering some optimizations or other areas for improvement along the way. Great job to all those at CodeWeavers for continuing to enhance upstream Wine.