GetFrameTimings not works in c#?

[Zaetc]

GetFrameTiming works fine. (it ok, but it is not optimal way if you need get many Compositor_FrameTiming)
But GetFrameTimings brings to crashes (System.AccessViolationException).
May be I'm doing something wrong?
Here is code:

 private Compositor_FrameTiming[] GetFrames2()
        {
            Compositor_FrameTiming[] framestimesBuffer = new Compositor_FrameTiming[40];
            framestimesBuffer[0].m_nSize = Convert.ToUInt32(System.Runtime.InteropServices.Marshal.SizeOf(typeof(Compositor_FrameTiming)));
            uint ft = OpenVR.Compositor.GetFrameTimings(ref framestimesBuffer[0], 40);
            if (ft != 40)
            {
                /// do sometning
            }
            return framestimesBuffer;
        }

[BOLL7708]

I noticed this as well, so I just went with grabbing the frame timing very often instead, as I'm doing live frame timing analysis. It's a while since I looked at this, I think loading timings worked if I only asked for 1-2 frames, which made it kind of pointless, if I actually remember it correctly.

[aleiby]

That function is missing the proper mark up to have it export properly in the C# bindings. Here's what you can do to change this locally until we get a new version of the SDK updated with the fix.

[UnmanagedFunctionPointer(CallingConvention.StdCall)]
internal delegate uint _GetFrameTimings([In, Out] Compositor_FrameTiming[] pTiming, uint nFrames);
[MarshalAs(UnmanagedType.FunctionPtr)]
internal _GetFrameTimings GetFrameTimings;

public uint GetFrameTimings(Compositor_FrameTiming [] pTiming)
{
	uint result = FnTable.GetFrameTimings(pTiming,(uint) pTiming.Length);
	return result;
}

Then you just call like:

var timing = new Compositor_FrameTiming[8];
timing[0].m_nSize = (uint)System.Runtime.InteropServices.Marshal.SizeOf(typeof(Compositor_FrameTiming));
vr.compositor.GetFrameTimings(timing);

[aleiby]

Should be fixed in the next SDK update. Thanks!

[BOLL7708]

Thanks for replying here @aleiby, this got me to post about something else in the C# header I've been thinking about for a long time now 😅 I have a few other things regarding the header as well that I'll try to post eventually, need to do some more testing first though.

[BOLL7708]

@aleiby I finally got to updating my implementation, I'm providing an array Compositor_FrameTiming[] and the result count I get back matches the array size so it would appear to be working, but then all objects in the array are still empty (just instantiated with default primitives). Am I missing something here? 🤔 Meanwhile I can successfully get data from GetFrameTiming().

Could it be that the array reference is replaced while not passed as reference? I tried adding the key word but no difference on my end, so not sure. Did make a fiddle to check my sanity.