Java JNA mapping D2D1CreateFactory from D2D1

Question

I was trying to map the function D2D1CreateFactory from the DLL D2D1.dll. From there I want to build up on creating a Direct2D Java mapping, but that's off-topic. I so far had this:

public WinNT.HRESULT D2D1CreateFactory(int factoryType, REFIID riid, ID2D1Factory.ByReference ppIFactory);

The ID2D1Factory looks like this:

public class ID2D1Factory extends IUnknown {

    public ID2D1Factory() { }

    public ID2D1Factory(Pointer pvInstance) {
        super(pvInstance);
    }

}

When I try to run my code using the code below, "java.lang.Error: Invalid memory access" is thrown (when turning on JNA.setProtected()).

The code to run:

ID2D1Factory.ByReference ref= new ID2D1Factory.ByReference();
D2D1.INSTANCE.D2D1CreateFactory(0, new REFIID(new IID("06152247-6f50-465a-9245-118bfd3b6007").toByteArray()), ref);

I have no clue why. Is there anything I am doing wrong?

EDIT: Thanks to technomage I was able to get the correct method declaration. The method should be declared like this:

public WinNT.HRESULT D2D1CreateFactory(int factoryType, REFIID riid, D2D1_FACTORY_OPTIONS opts, PointerByReference pref);

The D2D1_FACTORY_OPTIONS structure was mapped as following:

public static class D2D1_FACTORY_OPTIONS extends Structure {
    public int debugLevel;
    protected List<String> getFieldOrder() {
        return Arrays.asList(new String[] { "debugLevel" });
    }
    public D2D1_FACTORY_OPTIONS() {}
    public D2D1_FACTORY_OPTIONS(int size) {
        super(new Memory(size));
    }
    public D2D1_FACTORY_OPTIONS(Pointer memory) {
        super(memory);
        read();
    }
}

Finally, the snippet to call the method:

D2D1_FACTORY_OPTIONS opts = new D2D1_FACTORY_OPTIONS();
PointerByReference pp = new PointerByReference();
D2D1.INSTANCE.D2D1CreateFactory(0, new REFIID(new IID("06152247-6f50-465a-9245-118bfd3b6007").toByteArray()), opts, pp);

Answer 1

According to this reference, D2D1CreateFactory requires pointer types as third and fourth arguments (you are declaring only three arguments).

Assuming you insert the options pointer (a simple struct *), your final argument needs to be PointerByReference, since the function will be "returning" a pointer value in the address that you give it.

You can then use PointerByReference.getValue() to initialize a new ID2D1Factory instance (the Structure.ByReference in this case is superfluous, since by default all structures as function parameters are treated as struct * by JNA unless explicitly defined otherwise).

public WinNT.HRESULT D2D1CreateFactory(int factoryType, REFIID riid, D2D1_FACTORY_OPTIONS options, ID2D1Factory ppIFactory);

public class D2D1_FACTORY_OPTIONS extends Structure { ... }

D2D1_FACTORY_OPTIONS options = ...;
PointerByReference pref = new PointerByReference();

D2D1.INSTANCE.D2D1CreateFactory(0, new REFIID(...), options, pref);
ID2D1Factory factory = new ID2D1Factory(pref.getValue());

And don't forget to call Structure.read() in your ID2D1Factory(Pointer) ctor.