But then you assume that all objects implementing the interface will use the same struct layout for that. I can't think of an example inside MSHTML where it's currently not the case, but that's not generally a promise that QI gives.
In theory, there's a similar concern when looking up the function via IID and DISPID, specifically, that it might find a different function. In practice as you said it probably doesn't happen but…
So what's the point of it then? Avoiding one argument in a call?
Continuing the above, IMO the following would make it the most robust: we look it up as mentioned from the func_info_t's dispid and IID, and then compare to see if it's the same `func_info_t` pointer. If not, return E_UNEXPECTED since it's the wrong function. And yes, one less argument to keep track of, but also one less thing to keep track of (in the ProxyFunction for instance, and everywhere else).
I think that you misinterprets your observations. Here is a test proving that currentStyle should have a setter that throws an error (unless used for modifiable style object):
Okay, thanks for the test, I guess there's more at play here indeed.
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Gabriel Ivăncescu (＠insn)