RenderModel_TextureMap_(packed_)t Incorrect data types in C#

[jstefanelli]

The current implementation of the 2 strucures in openvr_api.cs is:

[StructLayout(LayoutKind.Sequential)]
public struct RenderModel_TextureMap_t
{
	public char unWidth;
	public char unHeight;
	public IntPtr rubTextureMapData; // const uint8_t *
}

// This structure is for backwards binary compatibility on Linux and OSX only
[StructLayout(LayoutKind.Sequential, Pack = 4)]
public struct RenderModel_TextureMap_t_Packed
{
	public char unWidth;
	public char unHeight;
	public IntPtr rubTextureMapData; // const uint8_t *

	public RenderModel_TextureMap_t_Packed(RenderModel_TextureMap_t unpacked)
	{
		this.unWidth = unpacked.unWidth;
		this.unHeight = unpacked.unHeight;
		this.rubTextureMapData = unpacked.rubTextureMapData;
	}

	public void Unpack(ref RenderModel_TextureMap_t unpacked)
	{
		unpacked.unWidth = this.unWidth;
		unpacked.unHeight = this.unHeight;
		unpacked.rubTextureMapData = this.rubTextureMapData;
	}
}

Where, according to the docs, the fields unWidth and unHeight are supposed to be ushort.

Manually changing these in the file solves a problem with Render Model Texture Loading.
(Example: with the non midified structures, loading the model vr_controller_vive_1_5 returns a 0x8 px texture.)

[aleiby]

This is to wrap the following C structure which uses uint16_t for width and height:
https://github.com/ValveSoftware/openvr/blob/master/headers/openvr.h#L3159

char in C# is 16-bits (as opposed to 8-bits in C). I'm not sure why it was used rather than ushort.
https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/char

[jstefanelli]

It should work in theory, but without changing the values to ushort i got incorrect texture sizes. Is it possible that I may have loaded it wrong?

[SpyderTL]

The problem is actually the Interop Marshall PtrToStructure method. When converting between safe and unsafe code, char fields are converted to/from 1 byte chars, by default.

https://blogs.msdn.microsoft.com/hongmeig/2004/08/19/marshal-sizeoftypeofchar-is-not-equal-to-sizeofchar/

Adding a CharSet attribute to the structure should also work. (Although I prefer changing the field to ushort)

https://msdn.microsoft.com/en-us/library/system.runtime.interopservices.charset(v=vs.110).aspx

[deranen]

Waiting for this to be fixed. It's been 9 months now.