a-b-street/abstreet · critical · anyhow::Error

error compiling shader

Error message

error compiling shader: {}

What it means

compile_shader in widgetry's glow backend wraps OpenGL shader compilation: it uploads the shader source, compiles it, and if the driver reports a compile failure it bails with the driver's info log. The message is a low-level rendering backend error surfacing a GLSL problem.

Solutions

  1. Read the info log appended to the error message and fix the GLSL syntax/feature it points to
  2. Update GPU drivers or run on hardware supporting the required OpenGL version
  3. Check the GLSL version header (#version) matches the context's supported version
  4. If the shader was recently changed, revert and re-apply the change carefully

Example fix

// before
#version 410 core
// after
#version 150 core // match the driver's supported GLSL version
Defensive patterns

Strategy: try-catch

Validate before calling

if !gl.get_shader_compile_status(shader) {
    eprintln!("shader log: {}", gl.get_shader_info_log(shader));
}

Try / catch

match widgetry_app::run(settings) {
    Ok(()) => {},
    Err(e) if e.to_string().starts_with("error compiling shader") => {
        eprintln!("GPU/driver rejected shader: {}\ntry updating drivers or another machine", e);
        std::process::exit(1);
    }
    Err(e) => return Err(e),
}

Prevention

When it happens

Trigger: Any widgetry program whose GLSL source fails to compile on the current GPU/driver, e.g. shader syntax errors, unsupported GLSL version directives, or features the driver rejects.

Common situations: Running on machines with old/limited GPU drivers, missing OpenGL version support (e.g. VMs or software renderers), recently modified shader code with a typo, driver-specific GLSL strictness.

Related errors

AI-assisted analysis of a-b-street/abstreet@0964f29315 (2026-09-13). Data as JSON: /api/errors/e58ee7cc43c787b0. Report an issue: GitHub.

Appendix: source

Thrown at widgetry/src/backend_glow.rs:67

        glow::ONE,
        glow::ONE_MINUS_SRC_ALPHA,
        glow::ONE_MINUS_DST_ALPHA,
        glow::ONE,
    );

    Ok(program)
}

unsafe fn compile_shader(
    gl: &glow::Context,
    shader_type: u32,
    shader_source: &str,
) -> anyhow::Result<glow::Shader> {
    let shader = gl.create_shader(shader_type).map_err(|e| anyhow!(e))?;
    gl.shader_source(shader, shader_source);
    gl.compile_shader(shader);
    if !gl.get_shader_compile_status(shader) {
        bail!("error compiling shader: {}", gl.get_shader_info_log(shader));
    }

    Ok(shader)
}

// Represents one frame that's gonna be drawn
pub struct GfxCtxInnards<'a> {
    gl: &'a glow::Context,
    current_clip: Option<[i32; 4]>,
    transform_location: <glow::Context as glow::HasContext>::UniformLocation,
    window_location: <glow::Context as glow::HasContext>::UniformLocation,
}

impl<'a> GfxCtxInnards<'a> {
    pub fn new(
        gl: &'a glow::Context,
        program: &'a <glow::Context as glow::HasContext>::Program,
    ) -> Self {

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