Nothing special, i.e. empty flag.

Flag indicating if geometry based anti-aliasing is used (may not be needed when using MSAA).

Flag indicating if strokes should be drawn using stencil buffer. The rendering will be a little * slower, but path overlaps (i.e. self-intersecting or sharp turns) will be drawn just once.

Flag indicating that additional debug checks are done.

Filter (antialias) fonts

Don't filter (antialias) fonts

You can use this as a substitute for default flags, for cases like this: nvgCreateContext(NVGContextFlag.Default, NVGContextFlag.Debug);.