slint-ui/slint · error

Cannot proceed without WebGL - aborting

Error message

Cannot proceed without WebGL - aborting

What it means

Error "Cannot proceed without WebGL - aborting" thrown in slint-ui/slint.

Source

Thrown at internal/renderers/femtovg/opengl.rs:136

        let gl_renderer = match femtovg::renderer::OpenGl::new_from_html_canvas(&html_canvas) {
            Ok(gl_renderer) => gl_renderer,
            Err(_) => {
                use wasm_bindgen::JsCast;

                // I don't believe that there's a way of disabling the 2D canvas.
                let context_2d = html_canvas
                    .get_context("2d")
                    .unwrap()
                    .unwrap()
                    .dyn_into::<web_sys::CanvasRenderingContext2d>()
                    .unwrap();
                context_2d.set_font("20px serif");
                // We don't know if we're rendering on dark or white background, so choose a "color" in the middle for the text.
                context_2d.set_fill_style_str("red");
                context_2d
                    .fill_text("Slint requires WebGL to be enabled in your browser", 0., 30.)
                    .unwrap();
                panic!("Cannot proceed without WebGL - aborting")
            }
        };

        let femtovg_canvas = femtovg::Canvas::new_with_text_context(
            gl_renderer,
            crate::font_cache::FONT_CACHE.with(|cache| cache.borrow().text_context.clone()),
        )
        .unwrap();

        *self.opengl_context.borrow_mut() = opengl_context;
        #[cfg(target_family = "wasm")]
        {
            *self.html_canvas.borrow_mut() = Some(html_canvas);
        }

        let canvas = Rc::new(RefCell::new(femtovg_canvas));
        renderer.reset_canvas(canvas);
        Ok(())

View on GitHub (pinned to 3fd8f2ec03)

Solutions

1. Serve the page in a browser with WebGL support enabled.
2. Use the software renderer fallback if WebGL is unavailable.

When it happens

Trigger: Thrown at internal/renderers/femtovg/opengl.rs:136 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of slint-ui/slint@3fd8f2ec03 (2026-08-19). Data as JSON: /api/errors/078a13d5c6fbaa5b. Report an issue: GitHub.