winit backend: Specified DOM element '{}' is not a HTML Canv

Error message

winit backend: Specified DOM element '{}' is not a HTML Canvas

What it means

Error "winit backend: Specified DOM element '{}' is not a HTML Canvas" thrown in slint-ui/slint.

Source

Thrown at api/wasm-interpreter/src/lib.rs:361

                if let Some(canvas_id) = next_id.borrow_mut().take() {
                    use i_slint_backend_winit::winit::platform::web::WindowAttributesExtWebSys;

                    use wasm_bindgen::JsCast;

                    let html_canvas = web_sys::window()
                        .expect("wasm-interpreter: Could not retrieve DOM window")
                        .document()
                        .expect("wasm-interpreter: Could not retrieve DOM document")
                        .get_element_by_id(&canvas_id)
                        .unwrap_or_else(|| {
                            panic!(
                                "wasm-interpreter: Could not retrieve existing HTML Canvas element '{}'",
                                canvas_id
                            )
                        })
                        .dyn_into::<web_sys::HtmlCanvasElement>()
                        .unwrap_or_else(|_| {
                            panic!(
                                "winit backend: Specified DOM element '{}' is not a HTML Canvas",
                                canvas_id
                            )
                        });
                    attrs = attrs
                        .with_canvas(Some(html_canvas))
                        // Don't activate the window by default, as that will cause the page to scroll,
                        // ignoring any existing anchors.
                        .with_active(false);
                    attrs
                } else {
                    attrs
                }
            })
        })
        .build()
        .unwrap();
    i_slint_core::platform::set_platform(Box::new(backend))

View on GitHub (pinned to 3fd8f2ec03)

Solutions

Pass the id of a <canvas> element, not a generic <div> or other DOM element.
Replace the referenced element with a real HTMLCanvasElement.

When it happens

Trigger: Thrown at api/wasm-interpreter/src/lib.rs:361 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/7baa8951d1a761d2. Report an issue: GitHub.