Windows Terminal HLSL Shader Compatibility

RoyalTerminal can load a supported subset of Windows Terminal-style HLSL pixel shaders and translate them into Skia Runtime Effect source. This is intended for common terminal post-process shaders such as CRT, scanline, hue-shift, and transparency-key effects.

This compatibility mode is source adaptation. RoyalTerminal does not currently invoke DXC, Direct2D, or the Windows Terminal rendering pipeline.

Full HLSL packages, compute shaders, multiple resources, and native DirectX execution are outside this path. Port those effects into the supported single-pass post-process shape before assigning them to ShaderSources.

Apply a Windows Terminal-style shader

using RoyalTerminal.Shaders;

Terminal.ShaderSources =
[
    new TerminalShaderSource(
        "Windows Terminal Compatible",
        """
        Texture2D shaderTexture : register(t0);
        SamplerState samplerState : register(s0);

        cbuffer PixelShaderSettings : register(b0)
        {
            float Time;
            float Scale;
            float2 Resolution;
            float4 Background;
        };

        struct PSInput
        {
            float4 pos : SV_POSITION;
            float2 uv : TEXCOORD;
        };

        float4 main(PSInput pin) : SV_TARGET
        {
            float4 color = shaderTexture.Sample(samplerState, pin.uv);
            color.rgb = lerp(color.rgb, float3(1.0, 0.75, 0.25), 0.12);
            return color;
        }
        """,
        TerminalShaderLanguage.WindowsTerminalHlsl)
];

The adapter strips the Windows Terminal resource declarations, creates equivalent Skia uniforms, and rewrites terminal texture sampling to the managed framebuffer input.

Supported source shape

Pattern	Status
Texture2D shaderTexture : register(t0);	Supported and removed during translation. Generic forms such as Texture2D<float4> are also accepted, and any Texture2D name bound to t0 is treated as the terminal frame.
SamplerState samplerState : register(s0);	Supported and removed during translation. The sampler variable name does not need to be samplerState.
cbuffer PixelShaderSettings : register(b0)	Supported and removed during translation.
struct PSInput { float4 pos; float2 uv; }	Supported and removed during translation. Input structs with SV_POSITION or TEXCOORD fields are also removed, including common aliases such as position and texCoord.
float4 main(PSInput pin) : SV_TARGET	Supported. The body becomes the Skia main(float2 fragCoord), and direct pin.pos/pin.uv or semantic field aliases are mapped to generated pos/uv values.
float4 main(float4 pos : SV_POSITION, float2 uv : TEXCOORD0)	Supported. Parameter names are normalized to generated pos and uv values.
shaderTexture.Sample(samplerState, uv)	Rewritten to sample the terminal frame.
shaderTexture.SampleLevel(samplerState, uv, lod)	Rewritten to sample the terminal frame. The explicit LOD is ignored by the Skia post-process path.
shaderTexture.SampleBias(...), shaderTexture.SampleGrad(...)	Rewritten to sample the terminal frame. Bias and gradient arguments are ignored by the Skia post-process path.
shaderTexture.Load(int3(pos.xy, 0))	Rewritten to sample the terminal frame with pixel coordinates.
#include "SHADERed/..."	Removed.
register(...) annotations	Removed.
HLSL float suffixes such as 1.0f	Removed.
static const values	Normalized to Skia const declarations.
min10float, min16float vector types	Normalized to Skia half vector types.

The generated Skia entry point provides:

float4 pos = float4(fragCoord, 0.0, 1.0);
float2 uv = fragCoord / Resolution;

That matches the common Windows Terminal sample shape where pin.pos is pixel-space and pin.uv is normalized.

Supported built-in replacements

HLSL	Skia Runtime Effect
lerp(a, b, t)	mix(a, b, t)
frac(x)	fract(x)
fmod(a, b)	mod(a, b)
saturate(x)	clamp(x, 0.0, 1.0)
atan2(y, x)	atan(y, x)
rsqrt(x)	inversesqrt(x)
mad(a, b, c)	(a * b + c)
mul(a, b)	(a * b)

The adapter also normalizes a simple bitwise-or expression pattern used by some shader samples.

PixelShaderSettings uniforms

RoyalTerminal exposes the common Windows Terminal settings names:

Uniform	Meaning
Time	Elapsed shader time in seconds.
Scale	Avalonia render scale.
Resolution	Framebuffer size in pixels.
Background	Terminal background color.

If a source needs more terminal state, it can also declare the common RoyalTerminal uniforms listed in Shader Support.

Limitations

This is not a full HLSL compiler. It covers common Windows Terminal pixel shader samples, including the patterns used by many community CRT and color effects, but it will not compile every HLSL file.

Not currently supported:

• arbitrary HLSL syntax outside the supported pixel-shader shape
• additional textures, samplers, UAVs, or constant buffers
• multi-pass effects
• compute shaders
• external include files after translation
• DirectX-only intrinsics with no Skia equivalent
• semantic-dependent code that cannot be reduced to fragCoord, pos, and uv

When a shader fails translation or compilation, TerminalShaderPostProcessor.CompileLog contains the Skia compiler diagnostics for the generated source.

Demo sample relationship

The demo shader catalog includes Skia Runtime Effect ports inspired by common Windows Terminal shader samples and one Windows Terminal-style HLSL sample translated at runtime:

• CRT-style amber display
• hue shift
• transparent background keying
• retro scanlines
• Windows Terminal CRT

All samples remain cross-platform because execution happens through Skia Runtime Effect.