I'm doing bring-up of a proprietary engine on Steam Deck using compatibility layer Proton 7.0-4 and OS version 3.3.1, Build 20220817.1, and the simple PSO for Dear imgui is suffering from a layout mismatch corrupting the UI rendering. Here's the HLSL versions:

Vertex shader:

struct PSInput { float2 TexCoord : TEXCOORD; float4 Color : COLOR; };
PSInput main(float2 Position : POSITION, float2 TexCoord : TEXCOORD, float4 Color : COLOR, out float4 OutPosition : SV_POSITION)
{
    OutPosition = mul(ProjectionMatrix, float4(Position, 0, 1));
    PSInput Result;
    Result.TexCoord = TexCoord;
    Result.Color = Color;
    return Result;
}

And pixel shader:

SamplerState TextureSampler : register(s0);
Texture2D Texture : register(t0);
float4 main(PSInput Input, float4 ScreenSpace : SV_POSITION) : SV_TARGET
{
    float4 SampledColor = Texture.Sample(TextureSampler, Input.TexCoord).aaaa;
    return (Texture.Sample(TextureSampler, Input.TexCoord) * Input.Color);
}

The first line in main() is vestigial, and always gets optimized out on Windows. The shaders are compiled using the legacy compiler via D3DCompile() and profiles vs_5_0 / ps_5_0

Looking at GLSL versions in a Renderdoc capture, the vertex shader declares its outputs as such:

layout(location = 2) out vec4 o2;

While the pixel shader declares its inputs as

layout(location = 1) in vec4 v1;

So vertex shader's o1 (tex coord) ends up going to the pixel shader's v1 (color), causing incorrect texcoords to be used for sampling the imgui texture and corrupted UI rendering.

The full shaders are attached as HLSL, SPIR-V, and GLSL; with the latter two obtained from a Renderdoc capture running remotely on the Steam Deck.

ps-glsl.txt
ps-hlsl.txt
ps-spirv.txt
vs-glsl.txt
vs-hlsl.txt
vs-spirv.txt