Please add an additional test that passes in non-null flags that
don't match
standard R5G6B5.
I'm not exactly sure what you mean with this. The other test has mask of R5G5B5. The one that's missing is R5G6B5, but I don't think it's needed.
E.g. a red mask of 0xf0f0, green 0x0f00 and blue 0x000f. The purpose is to find out if windows listens to non-zero masks. If it does you'll get 0 formats reported. If it doesn't you'll get the usual count.