slint-ui/slint · error

unable to show popup window

Error message

unable to show popup window

What it means

Slint panics when the window adapter refuses to make a popup window visible during `show_popup`. Popup windows are created internally when a component declares `show_popup`; the backend's `set_visible(true)` returned an Err, meaning the platform window could not be mapped/shown. This indicates a backend or platform-level failure, not a Slint API misuse.

Solutions

1. Verify the parent window is still visible and mapped before calling show_popup
2. Check the backend/platform supports top-level popups (winit backend with multi-window support) rather than a limited embedded backend
3. Update to a newer Slint version; popup handling across backends has changed over releases
4. Reproduce with the `testing` backend to see if it is backend-specific

Example fix

// before: showing a popup after window closed
window.show_popup(popup, position);

// after: guard on visibility/valid window
if window.is_visible() {
    window.show_popup(popup, position);
}

if !window.is_visible() { return; } // do not show popups on hidden windows
// plus: only call show_popup on backends with window support

fn can_show_popup(w: &slint::Window) -> bool { w.is_visible() }

When it happens

Trigger: Calling `show_popup` (or triggering it via a property/touch event) when the backend window adapter's `set_visible` fails — e.g. the underlying platform window was already destroyed, the display/connection is gone, or the backend does not support separate top-level popup windows.

Common situations: Running on embedded/backends without real multi-window support; showing a popup after the parent window was closed; Wayland/X11 connection lost; Android activity in background state.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

• context shouldn't have been set before
• Popup component is a Window item
• It must be there because we set the global
• slint_testing_use_native_popup called without testing…
• window_adapter just initialized above

AI-assisted analysis of slint-ui/slint@3a7e700487 (2026-09-16). Data as JSON: /api/errors/cae42effa3e768ca. Report an issue: GitHub.

Appendix: source

Thrown at internal/core/window.rs:2161

                    &clip_region,
                );
                self.window_adapter().request_redraw();
                (
                    PopupWindowLocation::ChildWindow(rect.origin),
                    Box::pin(PropertyTracker::new_with_dirty_handler(
                        PopupWindowPropertiesTracker {
                            parent_window_adapter_weak: parent_window_adapter_weak.clone(),
                            popup_id,
                        },
                    )),
                )
            } else {
                let popup_window = popup_window_adapter.window();
                WindowInner::from_pub(popup_window).set_component(popup_componentrc);
                popup_window.set_position(LogicalPosition::from_euclid(position));
                popup_window.set_size(WindowSize::Logical(LogicalSize::from_euclid(size)));

                popup_window_adapter.set_visible(true).expect("unable to show popup window");
                (
                    PopupWindowLocation::TopLevel(popup_window_adapter),
                    Box::pin(PropertyTracker::new_with_dirty_handler(
                        PopupWindowPropertiesTracker {
                            parent_window_adapter_weak: parent_window_adapter_weak.clone(),
                            popup_id,
                        },
                    )),
                )
            };

        let focus_item = if matches!(window_kind, WindowKind::ToolTip) {
            Default::default()
        } else {
            self.take_focus_item(&FocusEvent::FocusOut(FocusReason::PopupActivation))
                .map(|item| item.downgrade())
                .unwrap_or_default()
        };

View on GitHub (pinned to 3a7e700487)