zed-industries/zed · error

Failed to append canvas to body: {error:?}

Error message

Failed to append canvas to body: {error:?}

What it means

Guard in WebWindow::prepare_canvas: body.appendChild(canvas) threw — {error:?} is the JS exception, typically a HierarchyRequestError (body is not attached, e.g. detached document) or a CSP violation blocking DOM insertion.

Source

Thrown at crates/gpui_web/src/window.rs:111

pub struct WebWindow {
    inner: Rc<WebWindowInner>,
    display: Rc<dyn PlatformDisplay>,
    lifecycle: Rc<Cell<WebWindowLifecycle>>,
    active_window: Rc<RefCell<Option<AnyWindowHandle>>>,
    _raf_closure: Closure<dyn FnMut()>,
    _resize_observer: Option<web_sys::ResizeObserver>,
    _resize_observer_closure: Closure<dyn FnMut(js_sys::Array)>,
    _safe_area_observer: Option<web_sys::ResizeObserver>,
    _safe_area_observer_closure: Closure<dyn FnMut(js_sys::Array)>,
    _event_listeners: WebEventListeners,
}

impl WebWindow {
    pub(crate) fn prepare_canvas(
        browser_window: &web_sys::Window,
    ) -> anyhow::Result<web_sys::HtmlCanvasElement> {
        let document = browser_window
            .document()
            .ok_or_else(|| anyhow::anyhow!("No `document` found on window"))?;
        let canvas: web_sys::HtmlCanvasElement = document
            .create_element("canvas")
            .map_err(|error| anyhow::anyhow!("Failed to create canvas element: {error:?}"))?
            .dyn_into()
            .map_err(|error| anyhow::anyhow!("Created element is not a canvas: {error:?}"))?;
        canvas.set_tab_index(-1);

        let style = canvas.style();
        for (property, value) in [
            ("width", "100%"),
            ("height", "100%"),
            ("display", "block"),
            ("outline", "none"),
            ("touch-action", "none"),
            ("-webkit-touch-callout", "none"),
            ("user-select", "none"),
            ("-webkit-user-select", "none"),

View on GitHub (pinned to 9d272b0363)

Solutions

1. Ensure the body is connected to the document before appending the canvas
2. Check page CSP for restrictions on DOM modification
3. Report the JS exception so the embedding-page issue is visible in diagnostics

When it happens

Trigger: Thrown at crates/gpui_web/src/window.rs:107 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of zed-industries/zed@9d272b0363 (2026-08-20). Data as JSON: /api/errors/adba92a3f9111710. Report an issue: GitHub.