Problems getting a window capture with Bitblt and PrintWindow.

[VanGoghGaming]

Removed the "ByVal" from those two "DispCallFunc" parameters colored in red because "ByVal as Any" doesn't make much sense in my opinion:

Private Declare Function DispCallFunc Lib "oleaut32" (ByVal pvInstance As Long, ByVal oVft As Long, ByVal cc As Long, ByVal vtReturn As VbVarType,
ByVal cActuals As Long, ByVal prgvt As Any, ByVal prgpvarg As Any, ByRef pvargResult As Variant) As Long

Also rewrote those two "Invoke" functions as one to shave a few more milliseconds of execution speed. As far as I can see the behavior is exactly the same as it was before:

Private Function Invoke(ByVal pInterface As Long, ByVal vtb As vtb_Interfaces, ParamArray aParam()) As Variant
Dim i As Long, ParamValues(0 To 9) As Long, ParamTypes(0 To 9) As Integer, varParam As Variant, varRet As Variant
    If pInterface Then
        varParam = aParam
        For i = 0 To UBound(aParam)
            ParamTypes(i) = VarType(aParam(i))
            ParamValues(i) = VarPtr(varParam(i)) ' VarPtr(aParam(i)) <-- This doesn't work... Why?
        Next i
        Call DispCallFunc(pInterface, vtb * 4, CC_STDCALL, vbLong, i, ParamTypes(0), ParamValues(0), varRet)
        Invoke = varRet
    End If
End Function

I'm still not clear why does the ParamArray need to be saved in a local variant before being processed. Maybe someone more savvy with these intricacies could shed some light into the matter?

EDIT: I think this article does a pretty good job at explaining this scenario.