Yeah, pywin32 will see a byref ui1 and pass the address of an integer
filled with the value of the integer objects. However, I'm not really
sure what you are expecting this to do - passing the address of a Python
integer object clearly isn't correct - or to put it another way - what
exact are you hoping to pass as this parameter?
We could probably special-case VT_BYREF | VT_UI1 when a Python "buffer"
object is passed and pass the address of that buffer - this already
happens for a VT_ARRAY | VT_UI1 - but whether that would solve your
problem depends on how you actually intend using that param...
Mark.
On 29/05/2013 4:26 AM, Jeremy Kloth wrote:
I have been struggling with getting pointer parameters to work with the
COM interface for VirtualBox. In particular, the IFramebuffer
interface. I cannot seem to get the following to give the expected results:
interface IFramebuffer : IDispatch
{
// snipped to just the interesting definition
HRESULT RequestResize (
[in] ULONG aScreenId,
[in] ULONG aPixelFormat,
[in] BYTE * aVRAM,
[in] ULONG aBitsPerPixel,
[in] ULONG aBytesPerLine,
[in] ULONG aWidth,
[in] ULONG aHeight,
[out, retval] BOOL * aFinished
);
};
The type for aVRAM ends up being (correctly) VT_BYREF | VT_UI1.
Unfortunately PyIDispatch (incorrectly) converts the parameter to just
VT_UI1. The offending code path is: PyGatewayBase::Invoke() ->
invoke_setup() -> PyCom_PyObjectFromVariant() -> VariantCopyInd().
My not so informed understanding is that pythoncom considers all
VT_BYREF parameters as out-type parameters whereas, in this case at
least, it is not always such. Indeed, in this case, the aVRAM parameter
needs to be the *address* not the *value* for an object to implement
IFramebuffer properly.
Note that the object implementing IFramebuffer is passed as argument to
another function much the same way as event listeners.
I believe the fix involves PyIDispatch somehow using the type
information to determine which parameters are not out-type and then to
not dereference those.
Any direction with this is greatly appreciated.
Jeremy Kloth
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