If NULL is passed for the pIconInfo parameter, the caller is asking for the size of the ICONINFO buffer needed for this instance (usually for memory allocation purposes). Otherwise, the pIconInfo parameter can always be assumed to be large enough to accommodate the ICONINFO buffer and the variable data.
Note that the ICONINFO structure allows you to specify the default icon in three different ways:
However, only one mechanism need be supported. For example, a caller cannot request one of the three formats by prefilling the ICONINFO structure.