Stock Unity UI Stencil usage?

Do the default UI & mask shaders write to the stencil buffer? If so, do they use a known WriteMask and ReadMask? I see a number of stencil properties in the default UI shader.

 

I just found this for HDRP: There are 2 "User Bits":
UserBit0: 64 (0b1000000)
UserBit1: 128 (0b10000000)


That information can be found here: https://docs.unity3d.com/Packages/c...endering.HighDefinition.UserStencilUsage.html
or in an example here: https://github.com/alelievr/HDRP-Cu.../Assets/CustomPasses/SeeThrough/SeeThrough.cs

The other bits are used by unity, which is listed here:
https://github.com/Unity-Technologi...Runtime/RenderPipeline/HDStencilUsage.cs.hlsl

Code (CSharp):

1.  
2. #define STENCILUSAGE_CLEAR (0)
3. #define STENCILUSAGE_REQUIRES_DEFERRED_LIGHTING (2)
4. #define STENCILUSAGE_SUBSURFACE_SCATTERING (4)
5. #define STENCILUSAGE_TRACE_REFLECTION_RAY (8)
6. #define STENCILUSAGE_DECALS (16)
7. #define STENCILUSAGE_OBJECT_MOTION_VECTOR (32)
8. #define STENCILUSAGE_EXCLUDE_FROM_TAA (2)
9. #define STENCILUSAGE_DISTORTION_VECTORS (4)
10. #define STENCILUSAGE_SMAA (4)
11. #define STENCILUSAGE_WATER_SURFACE (16)
12. #define STENCILUSAGE_AFTER_OPAQUE_RESERVED_BITS (56)
13. #define STENCILUSAGE_USER_BIT0 (64)
14. #define STENCILUSAGE_USER_BIT1 (128)
15. #define STENCILUSAGE_HDRPRESERVED_BITS (63)
16.  

These values can also be found in the internal enum: "UnityEngine.Rendering.HighDefinition.StencilUsage" which you can decompile by ctrl-clicking the word "StencilUsage" in Visual Studio.