# How to Implement a Custom Input Panel Synced with a Webview in Tauri

> Sync a custom input panel with a Tauri webview by invoking Rust commands from React. Execute JavaScript in your webview for instant state synchronization. Learn how.

- Repository: [lencx/ChatGPT](https://github.com/lencx/ChatGPT)
- Tags: how-to-guide
- Published: 2026-03-06

---

**To sync a custom input panel with a Tauri webview, invoke Rust commands from your React frontend that use the `eval` method to execute JavaScript directly inside the target webview, enabling instantaneous state synchronization.**

The **lencx/ChatGPT** desktop application demonstrates this pattern by splitting its interface into multiple webview panels—specifically the `ask` panel for input and the `main` panel for the chat interface. By leveraging Tauri’s command bridge and the `eval` API, the application keeps a native-feeling input component perfectly synchronized with the underlying web content without embedding the input inside the webview itself.

## Architecture Overview

The synchronization relies on a four-layer architecture that separates the native input UI from the webview content while maintaining real-time communication:

- **React UI Layer**: Renders the textarea, manages local state, and debounces sync calls to avoid overwhelming the bridge.
- **Tauri Command Bridge**: Exposes Rust functions (`ask_sync`, `ask_send`) that receive data from the frontend.
- **Webview Evaluator**: Executes JavaScript inside the `main` webview using Tauri’s `eval` method to update the webview’s internal state.
- **Global JavaScript Interface**: A `ChatAsk` object exposed on `window` inside the webview that receives commands from Rust.

This flow allows the native panel to handle OS-level focus, keyboard shortcuts, and input validation, while the webview manages the actual conversation state and API communication.

## Creating the React Input Component

The custom input panel lives in [`src/view/Ask.tsx`](https://github.com/lencx/ChatGPT/blob/main/src/view/Ask.tsx) and uses React hooks to manage state and side effects. The component never directly manipulates the webview DOM; instead, it delegates all webview interactions to Tauri commands.

### Managing State and Debounced Synchronization

User input is stored in React state and synchronized to the webview using a debounced effect to prevent excessive cross-boundary calls:

```tsx
import { useState, useEffect, useRef } from 'react';
import { invoke } from '@tauri-apps/api/core';
import debounce from 'lodash/debounce';

export default function ChatInput() {
  const [message, setMessage] = useState('');
  const inputRef = useRef<HTMLTextAreaElement>(null);

  useEffect(() => {
    const syncMessage = debounce(async () => {
      await invoke('ask_sync', { message: JSON.stringify(message) });
    }, 300);
    syncMessage();
    return () => syncMessage.cancel();
  }, [message]);

  return (
    <textarea
      ref={inputRef}
      value={message}
      onChange={e => setMessage(e.target.value)}
      className="w-full h-full resize-none"
      autoFocus
    />
  );
}

```

The `invoke('ask_sync')` call serializes the message and passes it to the Rust backend, where it is injected into the webview’s JavaScript context.

### Handling Submission and Focus Restoration

When the user submits the message (via Cmd/Ctrl+Enter), the component triggers a send command and clears its state:

```tsx
const handleSend = async () => {
  if (!message) return;
  await invoke('ask_send');
  setMessage('');
  inputRef.current?.focus();
};

```

The `ask_send` command handles the actual submission inside the webview and manages focus restoration back to the input panel after a short delay.

## Bridging to the Webview with Rust Commands

In [`src-tauri/src/core/cmd.rs`](https://github.com/lencx/ChatGPT/blob/main/src-tauri/src/core/cmd.rs), two commands manage the communication between the native input and the webview content. Both commands access the `main` webview within the `core` window and evaluate JavaScript strings directly.

### Implementing ask_sync

The `ask_sync` command takes the JSON-serialized message and calls `ChatAsk.sync()` inside the webview:

```rust
#[command]
pub fn ask_sync(app: AppHandle, message: String) {
    app.get_window("core")
        .unwrap()
        .get_webview("main")
        .unwrap()
        .eval(&format!("ChatAsk.sync({})", message))
        .unwrap();
}

```

This evaluates the JavaScript immediately, allowing the webview to update its preview or draft state without a full page reload.

### Implementing ask_send with Focus Management

The `ask_send` command triggers the submission and returns focus to the input panel:

```rust
#[command]
pub fn ask_send(app: AppHandle) {
    let win = app.get_window("core").unwrap();
    win.get_webview("main")
        .unwrap()
        .eval(
            r#"
            ChatAsk.submit();
            setTimeout(() => {
                __TAURI__.webview.Webview.getByLabel('ask')?.setFocus();
            }, 500);
            "#,
        )
        .unwrap();
}

```

The `setTimeout` ensures the webview has processed the submission before returning focus to the `ask` panel webview.

## Dispatching Views Based on Webview Labels

Tauri applications can host multiple webviews simultaneously. In [`src/App.tsx`](https://github.com/lencx/ChatGPT/blob/main/src/App.tsx), the application determines which component to render based on the current webview’s label:

```tsx
import { getCurrentWebview } from '@tauri-apps/api/webview';
import Titlebar from '~view/Titlebar';
import Ask from '~view/Ask';
import Settings from '~view/Settings';

const viewMap = {
  titlebar: <Titlebar />,
  ask: <Ask />,
  settings: <Settings />,
};

export default function App() {
  const webview = getCurrentWebview();
  return viewMap[webview.label as keyof typeof viewMap] || null;
}

```

This design allows the `Ask` component to run in complete isolation as a separate webview (`ask`), while still controlling the `main` webview via the Rust command layer.

## Handling Messages in the Target Webview

For the Rust commands to function, the main webview must expose a global `ChatAsk` object. This is typically defined in the bundled frontend entry point (e.g., [`src/main.tsx`](https://github.com/lencx/ChatGPT/blob/main/src/main.tsx)):

```javascript
window.ChatAsk = {
  sync(msg) {
    console.log('Sync from native panel:', msg);
    // Update conversation preview or draft storage
  },
  submit() {
    console.log('Submit triggered from native panel');
    // Execute actual API call or chat submission
  },
};

```

The Rust side makes no assumptions about the internal implementation; it simply invokes these methods. This decoupling allows you to modify the webview’s internal logic without changing the native panel’s code.

## Summary

- **Use `invoke` from React** to send state changes to Rust commands, debouncing frequent updates like keystrokes to optimize performance.
- **Leverage `eval`** in Rust to execute JavaScript inside a specific webview, targeting the `main` webview to update its internal state via the `ChatAsk` interface.
- **Manage multiple webviews** by checking `getCurrentWebview().label` to render different components (titlebar, ask, settings) within the same application window.
- **Handle focus explicitly** using `__TAURI__.webview.Webview.getByLabel().setFocus()` to ensure smooth keyboard navigation between the native input and webview content.
- **Maintain separation of concerns** by keeping the input UI in a dedicated webview while the content lives in another, bridged only through typed commands.

## Frequently Asked Questions

### How do I prevent performance issues when syncing every keystroke to the webview?

Use a **debounce** function (such as `lodash/debounce`) to limit the frequency of `invoke` calls. In [`src/view/Ask.tsx`](https://github.com/lencx/ChatGPT/blob/main/src/view/Ask.tsx), the sync operation is wrapped in a 300ms debounce, ensuring the Rust bridge and `eval` calls only fire after the user pauses typing, preventing UI jank and excessive CPU usage.

### Can I send data from the webview back to the custom input panel?

Yes. While the example shows native-to-webview communication, you can implement bidirectional sync by using Tauri’s `emit` and `listen` event system. The webview can call `emit('update-input', data)` and the React layer can subscribe with `listen('update-input', handler)` to update the textarea state from webview interactions.

### Why use a separate webview for the input panel instead of embedding it in the main webview?

Separating the input into its own webview (labeled `ask`) provides **native OS integration** for focus management, keyboard shortcuts, and window controls that would be difficult to achieve inside a single webview. It also allows the input panel to persist and maintain state independently when the main webview navigates or reloads.

### What happens if the `ChatAsk` object is not defined in the main webview?

The `eval` call will throw a JavaScript error (`ReferenceError: ChatAsk is not defined`) which propagates to the Rust `unwrap()` call, potentially panicking the application. Always ensure the global interface is initialized in the frontend before the native panel sends commands, or add error handling in Rust using `if let` or `match` blocks instead of `unwrap()`.