Describe the Bug

The SteamVR OpenXR Windows runtime incorrectly exposes GL_RGBA16 via xrEnumerateSwapchainFormats.

Because standard SDK sample applications (like the official Khronos Group hello_xr reference sample) parse the runtime array and choose the highest-fidelity color depth available, hello_xr defaults to GL_RGBA16 out-of-the-box. While xrCreateSwapchain succeeds for the format, the moment the texture handles are passed to the compositor, ComposeLayerProjection fails entirely with VRCompositorError_TextureUsesUnsupportedFormat. Switching the selection logic manually to floating-point GL_RGBA16F fixes the bug completely.

A historical precedent exists for this issue: Valve explicitly resolved this exact behavior for Linux in SteamVR 1.24 ("xrEnumerateSwapchainFormats no longer returns the following formats on Linux as they are not properly supported: GL_RGBA16"). This cleanup was never ported to the Windows runtime side.

Environment & Reproducible Steps

1. OS: Windows 10/11 (Tested with NVIDIA driver stack nvwgf2umx.dll)
2. Runtime: SteamVR OpenXR Runtime
3. API: OpenGL
4. Application: Official Khronos OpenXR SDK sample (hello_xr using OpenGL graphics plugin module).
5. Out of the box, hello_xr enumerates the formats, evaluates 32859 (GL_RGBA16) as preferred, generates the color swapchain, and fails frame submission immediately. (hello_xr.exe -g OpenGL -ff Hmd -vc Stereo -v)

Raw Execution Logs

[Verbose] Swapchain Formats:  [32859] 34842 34843 35905 35907 [33189] 33190 36012
[Info   ] Creating color and depth swapchain for view 0 with dimensions Width=2496 Height=2688 SampleCount=1
[Info] - CreateSwapchain
[Info] -     format: 32859, sampleCount: 1
[Info] -     size: 2496 2688
[Info] - CreateSwapchain
[Info] -     format: 33189, sampleCount: 1
...
[Error] - ComposeLayerProjection: failed to submit view 0: VRCompositorError_TextureUsesUnsupportedFormat
[Error] - ComposeLayerProjection: failed to submit view 1: VRCompositorError_TextureUsesUnsupportedFormat

Exact Format Analysis

The Windows runtime is returning these precise decimal identifiers:
32859 34842 34843 35905 35907 33189 33190 36012

Here is what SteamVR is offering to the OpenXR layer:

Expected Behavior

SteamVR's Windows OpenXR runtime should strip GL_RGBA16 (32859) from the xrEnumerateSwapchainFormats return array. If the runtime cannot safely translate unorm 16-bit textures across its cross-API Vulkan interop path, it should not advertise them to OpenXR applications looking for a valid swapchain target.