Use the WOWCallback16Ex function in 32-bit code called from 16-bit code (through generic thunks) to call back to the 16-bit side (generic callback).
BOOL WINAPI WOWCallback16Ex(
DWORD vpfn16, // pointer to callback function
DWORD dwFlags, // flags
DWORD cbArgs, // byte count of pArgs arguments
PVOID pArgs, // arguments for callback function
PDWORD pdwRetCode // callback function return code
);
| WCB16_CDECL | Calls a _cdecl callback routine. |
| WCB16_PASCAL | Calls a _pascal callback routine (default). |
If cbArgs is larger than the WCB16_MAX_ARGS bytes that the system supports, the return value is FALSE and the GetLastError function returns the ERROR_INVALID_PARAMETER value. Otherwise, the return value is TRUE and the DWORD pointed to by pdwRetCode contains the return code from the callback routine. If the callback routine returns a WORD type instead of a DWORD type, the upper 16 bits of the return code are undefined and should be ignored by using LOWORD(dwRetCode).
WOWCallback16Ex allows any combination of arguments up to WCB16_MAX_CBARGS bytes total to be passed to the 16-bit callback routine. Regardless of the value of cbArgs, WCB16_MAX_CBARGS bytes will always be copied from pArgs to the 16-bit stack. If pArgs is less than WCB16_MAX_CBARGS bytes from the end of a page and the next page is inaccessible, WOWCallback16Ex will incur an access violation.
The arguments pointed to by pArgs must be in the correct order for the callback routine's calling convention. For example, to call a Pascal routine, place the arguments in the pArgs array in reverse order, with the least significant word first for DWORD types and offset first for FAR pointers.
When you call a _cdecl routine, place the arguments in the pArgs array in the order listed in the function prototype with the least significant word first for DWORD types and offset first for FAR pointers.