tauri-apps/tauri · critical

not implemented

Error message

not implemented

What it means

In Tauri's on_window_event handler, the DragDrop match falls through to an `unimplemented!()` catch-all for DragDropEvent variants other than Enter/Drop/Leave (e.g. DraggedOver/Dragged with payload variants not handled here). This is a deliberate internal placeholder: reaching it means a runtime drag-drop event shape the manager code was never written to handle. It panics (process abort of the event loop task) rather than returning a recoverable Result.

Solutions

1. Update Tauri to a version where all DragDropEvent variants are handled in on_window_event
2. File/check an upstream issue: this panic indicates a missing match arm in crates/tauri/src/manager/window.rs
3. As a workaround, avoid enabling drag-drop on windows until patched, or filter the event before it reaches the manager
4. If maintaining a fork, add explicit arms for the missing DragDropEvent variants (e.g. Dragged/DraggedOver) mirroring the Drop arm's emit logic

Example fix

// before
_ => unimplemented!(),
// after
DragDropEvent::DraggedOver { position } => {
  window.emit_to_window(DRAG_OVER_EVENT, &position)?
}
_ => Ok(()), // or log-and-ignore unknown variants

if let WindowEvent::DragDrop(e) = event {
  match e {
    DragDropEvent::Enter { .. } | DragDropEvent::Drop { .. } | DragDropEvent::Leave => {},
    other => eprintln!("unhandled drag-drop variant: {other:?}"),
  }
}

// unimplemented!() panics; it cannot be caught in Rust. Register on_window_event and ensure only supported variants flow, or wrap the app run in catch_unwind as a last resort:
std::panic::catch_unwind(|| tauri::Builder::default().run(ctx));

When it happens

Trigger: A WindowEvent::DragDrop variant other than the explicitly matched ones (Enter, Drop, Leave) reaches on_window_event via attach_window — i.e. the runtime emits a drag-drop sub-event (such as a drag-over/move variant) the manager has no arm for.

Common situations: Users dragging content over a Tauri window continuously (drag-over events) on platforms where the runtime forwards those variants; using a runtime/version combination where new DragDropEvent variants were added but manager/window.rs was not updated; custom event-loop integrations forwarding raw drag events.

Related errors

• not implemented
• cannot use both `resources` and `resources_map`
• failed to canonicalize global API script path
• failed to get exe directory
• failed to parse plugin global API script paths

AI-assisted analysis of tauri-apps/tauri@460ec35447 (2026-09-18). Data as JSON: /api/errors/943153629d75eac6. Report an issue: GitHub.

Appendix: source

Thrown at crates/tauri/src/manager/window.rs:269

            EmitPayload::Serialize(&payload),
          )?
        } else {
          window.emit_to_window(DRAG_DROP_EVENT, &payload)?
        }
      }
      DragDropEvent::Leave => {
        if window.is_webview_window() {
          // use underlying manager, otherwise have to recheck EventName
          window.manager().emit_to(
            EventTarget::labeled(window.label()),
            DRAG_LEAVE_EVENT,
            EmitPayload::Serialize(&()),
          )?
        } else {
          window.emit_to_window(DRAG_LEAVE_EVENT, &())?
        }
      }
      _ => unimplemented!(),
    },
    WindowEvent::ThemeChanged(theme) => window.emit_to_window(WINDOW_THEME_CHANGED, &theme)?,
    #[cfg(mobile)]
    WindowEvent::Suspended => window.emit_to_window(WINDOW_SUSPENDED_EVENT, &())?,
    #[cfg(mobile)]
    WindowEvent::Resumed => window.emit_to_window(WINDOW_RESUMED_EVENT, &())?,
  }
  Ok(())
}

#[derive(Clone, Serialize)]
#[serde(rename_all = "camelCase")]
struct ScaleFactorChanged {
  scale_factor: f64,
  size: PhysicalSize<u32>,
}

View on GitHub (pinned to 460ec35447)