Error, trying to add multiple children to a…

Error message

Error, trying to add multiple children to a circular-progress widget

What it means

Circular-progress is a GTK container subclass that accepts at most one child (the content widget). Its ContainerImpl::add checks whether content is already set; if so, it prints this error and removes the previous child rather than stacking widgets.

Solutions

Keep exactly one child inside the circular-progress widget in your config
Wrap multiple children in a `box` if you need a composite layout inside (though circular-progress expects a single content child)
Check custom widget definitions that might add extra children

Example fix

; before
(circular-progress
  (label :text "a")
  (label :text "b"))

; after
(circular-progress
  (box :orientation "v"
    (label :text "a")
    (label :text "b")))

Defensive patterns

Strategy: validation

Validate before calling

// ensure a single child before population
if children.len() > 1 {
    return Err(anyhow!("circular-progress accepts exactly one child"));
}

Try / catch

// treat as non-fatal: handler already prints and removes the old child
// ensure your config doesn't rely on multi-child behavior

Prevention

Give circular-progress exactly one child
Wrap composite layouts in a box inside the widget
Audit custom widgets that expand into circular-progress

When it happens

Trigger: The widget definition for a circular-progress contains two or more child widgets, so populate_widget_children calls add() a second time on the same instance.

Common situations: Accidentally leaving two children in the circular-progress element in yuck; a custom widget expansion that injects an extra child; refactoring a box into circular-progress without removing extra children.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

AI-assisted analysis of elkowar/eww@48f5aa8b37 (2026-09-08). Data as JSON: /api/errors/b099bc53bbdee510. Report an issue: GitHub.

Appendix: source

Thrown at crates/eww/src/widgets/circular_progressbar.rs:101

}

impl Default for CircProg {
    fn default() -> Self {
        Self::new()
    }
}

impl CircProg {
    pub fn new() -> Self {
        glib::Object::new::<Self>()
    }
}

impl ContainerImpl for CircProgPriv {
    fn add(&self, widget: &gtk::Widget) {
        if let Some(content) = &*self.content.borrow() {
            // TODO: Handle this error when populating children widgets instead
            error_handling_ctx::print_error(anyhow!("Error, trying to add multiple children to a circular-progress widget"));
            self.parent_remove(content);
        }
        self.parent_add(widget);
        self.content.replace(Some(widget.clone()));
    }
}

fn calc_widget_lowest_preferred_dimension(widget: &gtk::Widget) -> (i32, i32) {
    let preferred_width = widget.preferred_width();
    let preferred_height = widget.preferred_height();
    let min_lowest = i32::min(preferred_width.0, preferred_height.0);
    let natural_lowest = i32::min(preferred_width.1, preferred_height.1);
    (min_lowest, natural_lowest)
}

impl BinImpl for CircProgPriv {}

impl WidgetImpl for CircProgPriv {

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