slint-ui/slint · error

no simulated native drag in flight

Error message

no simulated native drag in flight

What it means

Error "no simulated native drag in flight" thrown in slint-ui/slint.

Source

Thrown at internal/backends/testing/testing_backend.rs:393

    /// the final negotiated action.
    pub fn simulate_native_drop(
        &self,
        target: &i_slint_core::api::Window,
        position: LogicalPosition,
    ) -> DragAction {
        let action = self.deliver_native_drag(target, position, true);
        WindowInner::from_pub(&self.window).report_drag_finished(action);
        action
    }

    fn deliver_native_drag(
        &self,
        target: &i_slint_core::api::Window,
        position: LogicalPosition,
        drop: bool,
    ) -> DragAction {
        let (data, allowed) =
            self.native_drag.borrow().clone().expect("no simulated native drag in flight");
        let mut event = DropEvent::default();
        event.data = data;
        event.position = position;
        event.proposed_action =
            i_slint_core::items::compute_proposed_action(Default::default(), allowed);
        let event = if drop {
            MouseEvent::Drop { event, allowed }
        } else {
            MouseEvent::DragMove { event, allowed }
        };
        WindowInner::from_pub(target).process_drag_event(event).unwrap_or(DragAction::None)
    }
}

impl WindowAdapterInternal for TestingWindow {
    fn input_method_request(&self, request: i_slint_core::window::InputMethodRequest) {
        self.ime_requests.borrow_mut().push(request)
    }

View on GitHub (pinned to 3fd8f2ec03)

Solutions

1. Start a simulated native drag before trying to complete or drop it.
2. Check the drag simulation call ordering in the test.

When it happens

Trigger: Thrown at internal/backends/testing/testing_backend.rs:393 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/4088cd629ec3926f. Report an issue: GitHub.