Why am I getting these errors, and do I need to include other header files?

Question

Why am I getting these errors, and do I need to include other header files?

CDev-8220 365

/* You can also use project link settings to explicitly link WindowsApp.lib.
Or, you can do it in source code (in pch.h, for example) like this. */
#pragma comment(lib, "windowsapp")
/* To use Windows Runtime (WinRT) APIs in your Win32 app, we use C++/WinRT.
The Windows SDK headers are the Windows Runtime ABI header files */
#include <windows.foundation.h>
#include <windows.ui.composition.interop.h>
/* all it takes to cause winrt::implements to support classic COM interfaces
is to include the unknwn.h header file before you include any C++/WinRT headers
You could do that explicitly, or indirectly by including some other header file
such as ole2.h. One recommended method is to include the wil\cppwinrt.h header
file, which is part of the Windows Implementation Libraries (WIL).
The wil\cppwinrt.h header file not only makes sure that unknwn.h is included
before winrt/base.h, it also sets things up so that C++/WinRT and WIL understand
each other's exceptions and error codes.
You can then as<> for classic COM interfaces, and the example code will compile */
#include <unknwn.h>
//#include <wil\cppwinrt.h>
/* include C++/WinRT headers */
#include <winrt/base.h>
#include "winrt/Windows.Foundation.h"
#include <winrt/Windows.UI.Composition.Desktop.h>
//#include <winrt/Windows.UI.Composition.h>
//#include <winrt/Windows.UI.Core.h>
#include <DispatcherQueue.h>
#include <presentation.h>
#pragma comment(lib, "dcomp.lib")

/* using namespace aliases for the different islands to deal with otherwise
potential namespace collisions between the C++/WinRT projection and the ABI. */
namespace winrt {
	using namespace winrt::Windows::System;
	using namespace winrt::Windows::UI;
	using namespace winrt::Windows::UI::Core;
	using namespace winrt::Windows::UI::Composition;
	using namespace winrt::Windows::UI::Composition::Desktop;
	using namespace winrt::Windows::Foundation;
	using namespace winrt::Windows::Foundation::Numerics;
}
/* ABI types found in the SDK header
Windows::Foundation, and all other Windows namespaces, are
declared by the SDK headers within the ABI namespace */
namespace abi {
	/* SDK Application Binary Interface, or ABI */
	using namespace ABI::Windows::System;
	using namespace ABI::Windows::UI;
	using namespace ABI::Windows::UI::Composition;
	using namespace ABI::Windows::UI::Composition::Desktop;
	using namespace ABI::Windows::Foundation;
	using namespace ABI::Windows::Foundation::Numerics;
}

I'm using HelloComposition example, and getting errors on the code in the AddCompositionElement function.

The first line of code in the function, auto visuals = m_DesktopWindowTarget.Root().as<abi::ContainerVisual>().Children(); returns these errors:

'ABI::Windows::UI::Composition::ContainerVisual': an undefined class is not allowed as an argument to compiler intrinsic type trait '__is_base_of' 'ABI::Windows::UI::Composition::ContainerVisual': an undefined class is not allowed as an argument to compiler intrinsic type trait '__is_base_of' 'ABI::Windows::UI::Composition::ContainerVisual': an undefined class is not allowed as an argument to compiler intrinsic type trait '__is_base_of' 'ABI::Windows::UI::Composition::ContainerVisual': an undefined class is not allowed as an argument to compiler intrinsic type trait '__is_base_of' 'ABI::Windows::UI::Composition::ContainerVisual': an undefined class is not allowed as an argument to compiler intrinsic type trait '__is_base_of' use of undefined type 'ABI::Windows::UI::Composition::ContainerVisual' 'void': all return expressions must deduce to the same type: previously it was 'T' use of undefined type 'ABI::Windows::UI::Composition::ContainerVisual' 'void': all return expressions must deduce to the same type: previously it was 'T' use of undefined type 'ABI::Windows::UI::Composition::ContainerVisual' use of undefined type 'ABI::Windows::UI::Composition::ContainerVisual'

CDev-8220 365 Reputation points

2025-05-30T19:06:31.17+00:00

I found out a possible reason for the error.

The error "an undefined class is not allowed as an argument to compiler intrinsic type trait '__is_base_of'" occurs when a class is used in a type trait before it is fully defined. This can happen when a class is referenced in a template or type trait before the class definition is complete, leading to a compile-time error.

The CompositionHost class was being declared after my main class, from which I was calling all the functions.

So the class was not fully declared before those function calls.

However, this is not the answer to the problem.

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CDev-8220 365 Reputation points

2025-05-30T19:06:31.17+00:00

I found out a possible reason for the error.

The error "an undefined class is not allowed as an argument to compiler intrinsic type trait '__is_base_of'" occurs when a class is used in a type trait before it is fully defined. This can happen when a class is referenced in a template or type trait before the class definition is complete, leading to a compile-time error.

The CompositionHost class was being declared after my main class, from which I was calling all the functions.

So the class was not fully declared before those function calls.

However, this is not the answer to the problem.

Answer 1

Darran Rowe 1,986

What are you trying to do here?

First of all, unless there is any reason to look elsewhere, if you are using C++/WinRT, you should always look in the winrt root namespace first. So winrt::Windows::UI::Composition::ContainerVisual would be what you want.

Secondly, this is important, the ABI should always be seen as a last resort. If you really need the ABI interface, and you don't in your sample above, then winrt::get_abi is what would be used to extract the ABI pointer. But it is extracted as a void * so understanding how these interfaces works is important.

CDev-8220 365 Reputation points

2025-05-30T19:28:12.2866667+00:00

Thanks.

First of all, unless there is any reason to look elsewhere, if you are using C++/WinRT, you should always look in the winrt root namespace first.

This is helpful, since I read that headers need to be directly included.

So winrt::Windows::UI::Composition::ContainerVisual would be what you want.

Does that exist?

I'm getting an error message that it does not.

Secondly, this is important, the ABI should always be seen as a last resort. If you really need the ABI interface, and you don't in your sample above, then winrt::get_abi is what would be used to extract the ABI pointer. But it is extracted as a void * so understanding how these interfaces works is important.

I don't need them. I left the ABI namespace there as an experiment.. and in the event they were needed.

Answer 2

Castorix31 90,191

I'm using HelloComposition example

The official MS sample https://github.com/microsoft/Windows.UI.Composition-Win32-Samples/tree/master/cpp/HelloComposition

works fine (by downloading all the repository from

https://github.com/microsoft/Windows.UI.Composition-Win32-Samples/tree/master)

CDev-8220 365 Reputation points

2025-05-30T17:59:14.4733333+00:00
I am sorry if I gave the impression that I am using a copy paste of the example.

I am actually coding from scratch, using this guide, since I want to know and understand the various "components", and at the same time utilize code, from the docs.

Some of these as you may have noticed, omits some lines used in the example.

For example...

Using this:

namespace winrt { using namespace winrt::Windows::System; using namespace winrt::Windows::UI; using namespace winrt::Windows::UI::Core; using namespace winrt::Windows::UI::Composition; using namespace winrt::Windows::UI::Composition::Desktop; using namespace winrt::Windows::Foundation; using namespace winrt::Windows::Foundation::Numerics; }

Omits having to use these lines of code in my functions.

namespace abi = ABI::Windows::UI::Composition::Desktop;

namespace abi = ABI::Windows::System;

I actually followed the steps outlined here, and got errors.

I'm wondering if the headers are fine, or if I am missing something.

I double checked, and think I got everything in place, but I am no expert at this, and figured one of you might spot something that was out of place.

I've been rechecking the code, but not finding what's wrong.

I'll take another look into it.
Darran Rowe 1,986 Reputation points

2025-05-30T18:08:48.1466667+00:00

I'm wondering if the headers are fine, or if I am missing something.

The only thing you are missing is that you are using the wrong type. You should be using winrt::Windows.UI.Composition::ContainerVisual. The as template on the projection types cannot be used to convert between a projection type and an ABI type.

If you need to use the ABI, which you don't here, the only way to get the ABI type out is winrt::get_abi.
CDev-8220 365 Reputation points

2025-05-30T19:22:33.5633333+00:00

Thanks.

I was looking into that, and wondering why the conversion was necessary, but not finding any information on it, and the example is not very well commented.

So how would I structure that line of code, instead?
CDev-8220 365 Reputation points

2025-05-30T20:11:50.4566667+00:00

The error went away, after changing the line of code to m_DesktopWindowTarget.Root().as<winrt::ContainerVisual>().Children();

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Why am I getting these errors, and do I need to include other header files?

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