[PATCH 6/9] dxgi: Implement d3d12_swapchain_GetBuffer().

[Józef Kucia]

Signed-off-by: Józef Kucia 
---
 dlls/dxgi/swapchain.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/dlls/dxgi/swapchain.c b/dlls/dxgi/swapchain.c
index 9112e7e70343..e0a148db3318 100644
--- a/dlls/dxgi/swapchain.c
+++ b/dlls/dxgi/swapchain.c
@@ -1014,10 +1014,18 @@ static HRESULT STDMETHODCALLTYPE d3d12_swapchain_Present(IDXGISwapChain3 *iface,
 static HRESULT STDMETHODCALLTYPE d3d12_swapchain_GetBuffer(IDXGISwapChain3 *iface,
         UINT buffer_idx, REFIID iid, void **surface)
 {
-    FIXME("iface %p, buffer_idx %u, iid %s, surface %p stub!\n",
+    struct d3d12_swapchain *swapchain = d3d12_swapchain_from_IDXGISwapChain3(iface);
+
+    TRACE("iface %p, buffer_idx %u, iid %s, surface %p.\n",
             iface, buffer_idx, debugstr_guid(iid), surface);

-    return E_NOTIMPL;
+    if (buffer_idx >= swapchain->buffer_count)
+    {
+        WARN("Invalid buffer index %u.\n", buffer_idx);
+        return DXGI_ERROR_INVALID_CALL;
+    }
+
+    return ID3D12Resource_QueryInterface(swapchain->buffers[buffer_idx], iid, surface);
 }

static HRESULT STDMETHODCALLTYPE DECLSPEC_HOTPATCH d3d12_swapchain_SetFullscreenState(IDXGISwapChain3 *iface,