CsWin32 generates IWICBitmapSource.CopyPixels extension method with in WICRect so NULL rectangle cannot be passed

[littletoxic]

Actual behavior

CsWin32 generates this friendly extension method:

internal static unsafe void CopyPixels(this winmdroot.Graphics.Imaging.IWICBitmapSource @this, in winmdroot.Graphics.Imaging.WICRect prc, uint cbStride, byte[] pbBuffer)

Because the first parameter is in WICRect, I cannot pass NULL for the rectangle. If I use default(WICRect) instead, the call does not behave like passing NULL (it copies a 0x0 region / returns all zeros).

Expected behavior

The native signature is:

unsafe void CopyPixels(winmdroot.Graphics.Imaging.WICRect* prc, uint cbStride, uint cbBufferSize, [Out] [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 2)] byte[] pbBuffer);

I expect CsWin32 to generate a safe overload that still allows passing a NULL rectangle (meaning “copy the whole image”), for example by using a nullable struct (WICRect?) or some other overload that can represent NULL.

Repro steps

1. NativeMethods.txt content:

// DXDemo1
GetModuleHandle
RegisterClass
CreateWindowEx
ShowWindow
PostQuitMessage
DefWindowProc
PeekMessage
TranslateMessage
DispatchMessage

WM_*

// DXDemo2
CoInitialize
D3D12GetDebugInterface
CreateDXGIFactory2
D3D12CreateDevice
MessageBox
CreateEvent
MsgWaitForMultipleObjects

ID3D12Debug
IDXGIFactory5
ID3D12Device4
ID3D12CommandQueue
ID3D12CommandAllocator
ID3D12GraphicsCommandList
ID3D12DescriptorHeap
IDXGISwapChain3
ID3D12Resource
ID3D12Fence

DXGI_ERROR_NOT_FOUND
INFINITE

// DXDemo3
D3D12SerializeRootSignature
D3DCompileFromFile

ID3D12PipelineState

D3D12_COLOR_WRITE_ENABLE

D3DCOMPILE_SKIP_OPTIMIZATION
D3DCOMPILE_DEBUG
D3D12_MIN_DEPTH
D3D12_MAX_DEPTH

// DXDemo4
CoCreateInstance

IWICImagingFactory
IWICPixelFormatInfo

CLSID_WICImagingFactory2
GUID_WICPixelFormat*
DXGI_FORMAT*
D3D12_TEXTURE_DATA_PITCH_ALIGNMENT
D3D12_DEFAULT_SHADER_4_COMPONENT_MAPPING
D3D12_FLOAT32_MAX


WaitForSingleObject

2. NativeMethods.json content (if present):

3. Any of your own code that should be shared?
   https://github.com/littletoxic/DXPractice/blob/master/DXDemo4/Program.cs#L467

	<PropertyGroup>
		<OutputType>WinExe</OutputType>
		<TargetFramework>net10.0-windows10.0.17763.0</TargetFramework>
		<ImplicitUsings>enable</ImplicitUsings>
		<PublishAot>true</PublishAot>
		<InvariantGlobalization>true</InvariantGlobalization>
		<CsWin32RunAsBuildTask>true</CsWin32RunAsBuildTask>
		<DisableRuntimeMarshalling>true</DisableRuntimeMarshalling>
	</PropertyGroup>

Context

• CsWin32 version: 0.3.264
• Win32Metadata version (if explicitly set by project): default
• Target Framework: net10.0-windows10.0.17763.0
• LangVersion (if explicitly set by project): default

[jevansaks]

The parameter is not [Optional] in metadata so that's why null is not allowed. Transferring to win32metadata.