libobs: Add function to enumerate video adapters

The gs_enum_adapters function is an optional implementation to allow
enumeration of available graphics adapters that can be used with the
program.  The ID associated with the adapter can be an index or a hash
depending on the implementation.

libobs-d3d11/d3d11-subsystem.cpp

@@ -469,6 +469,56 @@ const char *device_preprocessor_name(void)
 	return "_D3D11";
 }
 
+static inline void EnumD3DAdapters(
+		bool (*callback)(void*, const char*, uint32_t),
+		void *param)
+{
+	ComPtr<IDXGIFactory1> factory;
+	ComPtr<IDXGIAdapter1> adapter;
+	HRESULT hr;
+	UINT i = 0;
+
+	IID factoryIID = (GetWinVer() >= 0x602) ? dxgiFactory2 :
+		__uuidof(IDXGIFactory1);
+
+	hr = CreateDXGIFactory1(factoryIID, (void**)factory.Assign());
+	if (FAILED(hr))
+		throw HRError("Failed to create DXGIFactory", hr);
+
+	while (factory->EnumAdapters1(i++, adapter.Assign()) == S_OK) {
+		DXGI_ADAPTER_DESC desc;
+		char name[512] = "";
+
+		hr = adapter->GetDesc(&desc);
+		if (FAILED(hr))
+			continue;
+
+		/* ignore microsoft's 'basic' renderer' */
+		if (desc.VendorId == 0x1414 && desc.DeviceId == 0x8c)
+			continue;
+
+		os_wcs_to_utf8(desc.Description, 0, name, sizeof(name));
+
+		if (!callback(param, name, i - 1))
+			break;
+	}
+}
+
+bool device_enum_adapters(
+		bool (*callback)(void *param, const char *name, uint32_t id),
+		void *param)
+{
+	try {
+		EnumD3DAdapters(callback, param);
+		return true;
+
+	} catch (HRError error) {
+		blog(LOG_WARNING, "Failed enumerating devices: %s (%08lX)",
+				error.str, error.hr);
+		return false;
+	}
+}
+
 int device_create(gs_device_t **p_device, const gs_init_data *data)
 {
 	gs_device *device = NULL;