Ok, I see your point.
It is indeed weird, I didn't notice that, my appologies.
If you look at Volume.LockBox() for example you see this:
public GraphicsStream LockBox(Box box, LockFlags flags)
{
return this.LockBoxInternal(ref box, flags, 0);
}
Indeed weird why the box has to be passed by value and is then passed on
by ref. (LockBoxInternal accepts as 1st parameter _D3DBOX * )
One thing might be that manipulation of the passed in data is done on
the *copy*, not on the original, which might confuse people who are not
used to pointer arithmetic. To pass by value, you assure yourself you
have a copy, not the original. But that's just a wild guess.
FB
> Frans Bouma wrote:
> > Although there is one weird thing:
> > (and you know more on this than I do I think): the D3D structs are
> > redefined in these formats:
> >
> > [StructLayout(LayoutKind.Sequential, Size=24, Pack=1),
> > CLSCompliant(false), MiscellaneousBits(65), DebugInfoInPDB] public
> > struct _D3DBOX {
> >
> > }
> >
> > Without contents.
> >
> > Perhaps in combination with unmanaged code, I'm not sure.
>
> I think this is because D3DBOX is an unmanaged type and IIRC
> the content of the structure isn't available in the type
> library. From a managed perspective it is just a bunch of
> bytes (24 bytes, as you can see in the StructLayout
> attribute). In the Managed DirectX SDK there is probably a
> value type with the same layout and the wrapper just casts
> the pointer types. Something like this:
>
> [StructLayout(LayoutKind.Sequential, Size=24, Pack=1)] struct Box {
> uint Left;
> uint Top;
> uint Right;
> uint Bottom;
> uint Front;
> uint Back;
> }
>
> unsafe void SomeRandomBoxApi(Box b)
> {
> pComObject.SomeRandomBoxApi((_D3DBOX*)&b);
> }
>
> Now the question is, since SomeRandomBoxApi takes a pointer
> to a _D3DBOX (which is equivalent to a pointer to a Box), why
> pass in the Box by value?
>
> This would be (much?) more efficient:
>
> unsafe void SomeRandomBoxApi(ref Box b)
> {
> fixed(Box* p = &b)
> {
> pComObject.SomeRandomBoxApi((_D3DBOX*)p);
> }
> }
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