demo: call windows runtime from pure c

winrt.c

// please link with "runtimeobject.lib"

#include <roapi.h>
#include <winstring.h>

#include <windows.foundation.h>

#include <stdio.h>
#include <stdlib.h>

#define WIDEN2(x) L ## x
#define WIDEN(x) WIDEN2(x)
#define __WFILE__ WIDEN(__FILE__)

#define CHECK(hr)                                                               \
	do                                                                          \
	{                                                                           \
		if (FAILED(hr))                                                         \
		{                                                                       \
			wprintf_s(L"%s:%d: hr = 0x%08X\n", __WFILE__, __LINE__, hr); \
			exit(1);                                                       \
		}                                                                       \
	}                                                                           \
	while (0)

int wmain()
{
	HRESULT hr;

	hr = RoInitialize(RO_INIT_MULTITHREADED);

	CHECK(hr);

	{
		// some interfaces do not even have a C definition, e.g. IVector<T>, do they have an ABI?

		__x_ABI_CWindows_CFoundation_CIUriRuntimeClass *uri;

		{
			__x_ABI_CWindows_CFoundation_CIUriRuntimeClassFactory *uriFactory;

			{
				// not found in any .lib file, have to copy this from the header file
				// 
				// cd "C:\Program Files (x86)\Windows Kits\10\Lib\10.0.22621.0"
				// findstr /m /s /c:IUriRuntimeClassFactory *

				static const IID iid = { 0x44a9796f, 0x723e, 0x4fdf, {0xa2, 0x18, 0x03, 0x3e, 0x75, 0xb0, 0xc0, 0x84 } };

				HSTRING_HEADER runtimeClassStringHeader;
				HSTRING runtimeClassString;

				hr = WindowsCreateStringReference(
					RuntimeClass_Windows_Foundation_Uri,
					sizeof RuntimeClass_Windows_Foundation_Uri / sizeof(WCHAR) - 1,
					&runtimeClassStringHeader,
					&runtimeClassString);

				CHECK(hr);

				hr = RoGetActivationFactory(
					runtimeClassString,
					&iid,
					&uriFactory);

				CHECK(hr);
			}

			{
				static const WCHAR uriData[] = L"https://learn.microsoft.com/en-us/cpp/cppcx/wrl/how-to-activate-and-use-a-windows-runtime-component-using-wrl?view=msvc-170";

				HSTRING_HEADER uriStringHeader;
				HSTRING uriString;

				hr = WindowsCreateStringReference(
					uriData,
					sizeof uriData / sizeof(WCHAR) - 1,
					&uriStringHeader,
					&uriString);

				CHECK(hr);

				hr = uriFactory->lpVtbl->CreateUri(uriFactory, uriString, &uri);

				CHECK(hr);
			}

			uriFactory->lpVtbl->Release(uriFactory);
		}

		{
			HSTRING string;

			hr = uri->lpVtbl->get_Domain(uri, &string);

			CHECK(hr);

			wprintf_s(L"domain is \"%s\"\n", WindowsGetStringRawBuffer(string, 0));

			WindowsDeleteString(string);
		}

		{
			HSTRING string;

			hr = uri->lpVtbl->get_Path(uri, &string);

			CHECK(hr);

			wprintf_s(L"path is \"%s\"\n", WindowsGetStringRawBuffer(string, 0));

			WindowsDeleteString(string);
		}

		uri->lpVtbl->Release(uri);
	}

	RoUninitialize();

	return 0;
}