iced-rs/iced · error

Editor cannot have multiple strong references

Error message

Editor cannot have multiple strong references

What it means

Editor::highlight needs exclusive mutable access: it Arc::try_unwraps the internal Arc<Internal> (editor.rs:842, same pattern as with_internal_mut at editor.rs:67). If any other strong reference exists, try_unwrap returns Err and expect("Editor cannot have multiple strong references") panics. Editor is cheap to clone precisely because it wraps an Arc, and every surviving clone blocks highlighting and mutation.

Solutions

1. Keep exactly one strong owner: never clone() the Editor; move or borrow it instead
2. For read-only sharing use editor.downgrade() (a Weak reference), which does not block Arc::try_unwrap
3. Drop cached/cloned editors before driving update/highlight
4. Give each widget its own editor state instead of sharing one instance

Example fix

// before
let editor_copy = editor.clone(); // kept in a cache
editor.highlight(font, &mut hl, fmt); // panics: clone still alive

// after - share read access via Weak
debug_snapshot(editor); // reads bounds only
let weak = editor.downgrade(); // Weak does not block try_unwrap
drop(editor_copy);              // if a clone existed, release it first
editor.highlight(font, &mut hl, fmt);

// keep exactly one strong reference alive when mutating/highlighting
// drop any cached clones before the update/highlight cycle
drop(cached_editors.values()); // if you keep a map of clones, clear it first
editor.update(bounds, font, size, line_height, wrapping, alignment, hint, &mut highlighter);

When it happens

Trigger: Cloning the Editor (or the widget/tree holding it) and keeping the twin alive while the original is mutated/highlighted; caching editors in a map while also using them in the tree; two widgets sharing one editor instance.

Common situations: Stashing a copy of the editor for background measurement or persistence; splitting view/state ownership by cloning; reusing one editor across multiple text_editor-like widgets.

Related errors

• Editor should always be initialized
• Line layout should be cached
• Write font system
• Caches must not be empty
• Create color

AI-assisted analysis of iced-rs/iced@3de451447b (2026-08-17). Data as JSON: /api/errors/c733a0d879f62f42. Report an issue: GitHub.

Appendix: source

Thrown at graphics/src/text/editor.rs:842

                if window > visible_lines {
                    window -= visible_lines;
                    None
                } else {
                    Some(scroll.line + i)
                }
            })
            .unwrap_or(buffer.lines.len().saturating_sub(1));

        let current_line = highlighter.current_line();

        if current_line > last_visible_line {
            return;
        }

        let editor = self.0.take().expect("Editor should always be initialized");

        let mut internal =
            Arc::try_unwrap(editor).expect("Editor cannot have multiple strong references");

        let mut font_system = text::font_system().write().expect("Write font system");

        let attributes = text::to_attributes(font);

        for line in &mut buffer_mut_from_editor(&mut internal.editor).lines
            [current_line..=last_visible_line]
        {
            let mut list = cosmic_text::AttrsList::new(&attributes);

            for (range, highlight) in highlighter.highlight_line(line.text()) {
                let format = format_highlight(&highlight);

                if format.color.is_some() || format.font.is_some() {
                    list.add_span(
                        range,
                        &cosmic_text::Attrs {
                            color_opt: format.color.map(text::to_color),

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