Objects and Interfaces

Calling the IObjectName::QueryInterface method retrieves a valid interface pointer only if the object supports that interface; therefore, you could call the IDirect3DRMDevice::QueryInterface method to retrieve the IDirect3DRMWinDevice interface, but not to retrieve the IDirect3DRMVisual interface.

The following example illustrates how to create two interfaces to a single Direct3DRMDevice object. The IDirect3DRM::CreateObject method creates an uninitialized Direct3DRMDevice object. The IDirect3DRMDevice::InitFromClipper method initializes the object. The call to the IDirect3DRMDevice::QueryInterface method creates a second interface to the Direct3DRMDevice object-an IDirect3DRMWinDevice interface the application will use to handle WM_PAINT and WM_ACTIVATE messages.

d3drmapi->CreateObject(CLSID_CDirect3DRMDevice, NULL,

IID_IDirect3DRMDevice,(LPVOID FAR*)&dev1);

dev1->InitFromClipper(lpDDClipper, IID_IDirect3DRMDevice,

r.right, r.bottom);

dev1->QueryInterface(IID_IDirect3DRMWinDevice, (LPVOID*) &dev2);

To determine if two interfaces refer to the same object, call the QueryInterface method of each interface and compare the values of the pointers they return. If the pointer values are the same, the interfaces refer to the same object.

All Direct3D Retained-Mode objects support the IDirect3DRMObject and IUnknown interfaces in addition to the interfaces in the preceding list. Array objects are not derived from IDirect3DRMObject. Array objects have no class identifiers (CLSIDs) because they are not needed. Applications cannot create array objects in a call to the IDirect3DRM::CreateObject method; instead, they should use the creation methods listed below for each interface: