IDirect3DDevice9Ex::GetBackBuffer

DX9 vtable[18] → HRESULT

IDirect3DDevice9Ex::GetBackBuffer is a method of the COM interface IDirect3DDevice9Ex in Direct3D 9. Its function pointer sits at vtable index 18 — the zero-based slot in that interface's virtual method table, counted from QueryInterface and including every entry inherited from a base interface. It takes 4 parameters (swapchain_idx, backbuffer_idx, backbuffer_type, backbuffer) and returns HRESULT.

COM methods are reached through that table rather than by an exported name, so the slot index is what a wrapper, an interface hook or a disassembly listing has to resolve against. The parameter order and types below are the ones this interface declares.