ghostty-shaders

Ghostty Shaders

Ghostty compiles Shadertoy-compatible GLSL ES 3.0 (WebGL 2.0) with terminal-specific extensions. iChannel0 is the live terminal screen rather than an uploaded image, and the shader runs continuously while the terminal is visible — which makes performance and failure behavior matter more than they do on shadertoy.com.

A broken shader can lock you out

An invalid shader renders Ghostty as a black screen, including the window you would use to fix it. Keep a known-good shader to fall back to, build up from a passthrough rather than pasting a finished effect, and keep a non-Ghostty terminal reachable while iterating.

The compile failures that cause this are mostly a short list:

• 1.0f — no f suffix on float literals in GLSL ES
• saturate() — doesn't exist here; use clamp(x, 0.0, 1.0)
• Negative input to sqrt() or pow() — wrap with abs() or max(0.0, x)
• mod(x, 0.0) — division by zero
• Uninitialized variables — no implicit zero
• A function and a variable sharing a name

Configuration

# Single shader
custom-shader = ~/.config/ghostty/shaders/crt.glsl

# Multiple shaders chain: each one's output becomes the next one's iChannel0
custom-shader = ~/.config/ghostty/shaders/blur.glsl
custom-shader = ~/.config/ghostty/shaders/vignette.glsl

# Animation control
custom-shader-animation = true     # Default: animate when focused
custom-shader-animation = false    # Static: only render on terminal updates
custom-shader-animation = always   # Always animate (CPU intensive)

Entry point

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
    // fragCoord: pixel coordinates (0,0 = bottom-left)
    // fragColor: output RGBA color
    vec2 uv = fragCoord.xy / iResolution.xy;
}

Uniforms

Standard Shadertoy uniforms Ghostty provides:

sampler2D iChannel0;           // Terminal screen texture (or previous shader output)
vec3 iResolution;              // [width, height, 1.0] in pixels
float iTime;                   // Seconds since first frame
float iTimeDelta;              // Seconds since last frame
int iFrame;                    // Frame count
vec3 iChannelResolution[4];    // iChannelResolution[0] == iResolution