# WebView CEF

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**English** · [简体中文](README.zh-CN.md)

A Flutter **desktop** WebView backed by [CEF](https://bitbucket.org/chromiumembedded/cef) (Chromium Embedded Framework). It renders a full Chromium browser off-screen and presents it inside a Flutter `Texture`, so the web content composes natively with the rest of your Flutter UI on Windows, macOS, and Linux.

> Built on **CEF 149 (Chromium 149)**.

---

## Features

- 🌐 **Full Chromium engine** — modern web standards, WebGL, HTML5 video, and more.
- ⚡ **GPU zero-copy rendering** (Windows & macOS) — frames go straight from Chromium's GPU output to Flutter via a shared texture (a D3D11 texture on Windows, an IOSurface on macOS), with no per-frame CPU color-swizzle or CPU→GPU upload. Linux still uses the software path.
- 🎞️ **Adaptive frame rate** (Windows & macOS) — frame production is driven by the display's vblank (`IDXGIOutput::WaitForVBlank` on Windows, `CVDisplayLink` on macOS), so the webview tracks your monitor's real refresh rate (e.g. 120/144 Hz) instead of being capped at 60 fps. Static content stays idle.
- ⌨️ **Real-time CJK/IME input** — native composition pipeline; Chinese/Japanese/Korean preedit appears live and commits correctly.
- 🔌 **JavaScript bridge** — call into Dart from JS and evaluate JS from Dart.
- 🍪 **Cookie management** — read, set, and delete cookies.
- 🪟 **Multiple instances** — run several independent webviews at once.
- 📜 **User-script injection** — inject JS/CSS at document start or end.
- 🛠️ **DevTools**, mouse & trackpad input, navigation, and load/title/url events.

## Supported platforms

| Platform | Minimum version | Architectures |
| --- | --- | --- |
| Windows | Windows 10 | x64 |
| macOS  | macOS 12.0 | arm64, x86_64, or universal (arm64 + x86_64) |
| Linux  | — | x64, arm64 |
| eLinux | — | x64, arm64 |

## Requirements

- Flutter **>= 3.27.0**, Dart **>= 3.6.0** (tested against the latest stable Flutter, 3.44.x).
- A C++20 toolchain for the native side (required by CEF 149) — recent MSVC / Clang / GCC.

---

## Upgrading from ≤ 0.2.2

0.5.0 is a large upgrade (Flutter 3.44 + CEF 149) with breaking changes on every platform. If you are coming from an older release, do the following:

- **Toolchain** — upgrade to Flutter **≥ 3.27.0** / Dart **≥ 3.6.0** (was 2.5.0 / 2.17.1). The native build now requires **C++20** (CEF 149); make sure your app doesn't force the plugin target to an older C++ standard.
- **Removed Dart API** — `WebviewCefPlatform`, `MethodChannelWebviewCef`, and `getPlatformVersion()` were removed (along with the `plugin_platform_interface` dependency). They were never the intended API and have no replacement (`getPlatformVersion` returned a demo value). Import only `package:webview_cef/webview_cef.dart` and use `WebviewManager` / `WebViewController`.
- **Windows** — `initCEFProcesses` changed signature. Update `windows/runner/main.cpp`: it now takes the `HINSTANCE` and returns a sub-process exit code that must be returned immediately, as the first statement in `wWinMain` (see the Windows install snippet below). The minimum OS is now **Windows 10**.
- **macOS** — raise the deployment target to **12.0**: set `platform :osx, '12.0'` in `macos/Podfile` **and** the Runner target's macOS Deployment Target in Xcode (CEF 149's framework is built for 12.0). To enable multi-process rendering, add the one-line `post_install` hook to `macos/Podfile` (see the macOS install section). Builds target the **host architecture** by default (arm64 *or* x86_64); set `WEBVIEW_CEF_MACOS_ARCH=universal` before `pod install` for a universal (arm64 + x86_64) app.

---

## Installation

### Windows

1. Add the dependency:

   ```bash
   flutter pub add webview_cef
   ```

2. Edit `windows/runner/main.cpp`. Because of Chromium's multi-process architecture and to route input/IME and method-channel calls onto the Flutter engine thread, two hooks are required:

   ```cpp
   #include "webview_cef/webview_cef_plugin_c_api.h"

   int APIENTRY wWinMain(_In_ HINSTANCE instance, _In_opt_ HINSTANCE prev,
                         _In_ wchar_t *command_line, _In_ int show_command) {
     // Start the CEF sub-processes. MUST be the first thing in wWinMain.
     int exit_code = initCEFProcesses(instance);
     if (exit_code >= 0) {
       return exit_code;
     }
     // ... existing runner setup ...
   ```

   In the message loop, forward messages to CEF (enables keyboard input and lets CEF post to the Flutter engine thread):

   ```cpp
   ::MSG msg;
   while (::GetMessage(&msg, nullptr, 0, 0)) {
     ::TranslateMessage(&msg);
     ::DispatchMessage(&msg);
     handleWndProcForCEF(msg.hwnd, msg.message, msg.wParam, msg.lParam);
   }
   ```

   > IME is wired up automatically by the plugin — no extra runner code needed.

On the first build, the official CEF *Standard Distribution* (~330 MB, from <https://cef-builds.spotifycdn.com>) is downloaded into `third/cef` and `libcef_dll_wrapper` is compiled from source, so the first build takes noticeably longer.

### macOS

> **Requires macOS 12.0 or newer** — CEF 149 ships a framework with a 12.0 deployment target, so your app's macOS deployment target must be **≥ 12.0** (set it in `macos/Podfile` (`platform :osx, '12.0'`) and the Runner target). Older targets fail to link cleanly.

1. Add the dependency:

   ```bash
   flutter pub add webview_cef
   ```

2. Enable multi-process (recommended) by adding the helper hook to your `macos/Podfile`'s existing `post_install`:

   ```ruby
   post_install do |installer|
     installer.pods_project.targets.each do |target|
       flutter_additional_macos_build_settings(target)
     end
     # webview_cef: embed the CEF helper sub-process apps (multi-process).
     require File.expand_path(
       'Flutter/ephemeral/.symlinks/plugins/webview_cef/macos/embed_cef_helpers.rb', __dir__)
     WebviewCEF.install_helper_phase(installer)
   end
   ```

   Then `pod install` (run automatically by `flutter run`). This installs an "Embed CEF Helpers" build phase that clones the prebuilt helper into the five CEF sub-process `.app` bundles inside your app — no manual Xcode target needed. **Without this hook the plugin still works but falls back to single-process** (an unsupported Chromium mode: no crash isolation, V8 proxy resolver disabled, etc.).

macOS uses CocoaPods, which does not run the CMake download path. Instead the podspec's `prepare_command` runs [`macos/scripts/download_cef.sh`](macos/scripts/download_cef.sh) on `pod install`, which mirrors the Windows/Linux flow: it downloads the official CEF *Standard Distribution* for the selected architecture (from <https://cef-builds.spotifycdn.com>, version pinned by `CEF_VERSION` in [`third/download.cmake`](third/download.cmake)), compiles `libcef_dll_wrapper` from source, lays the framework out as a versioned macOS bundle, and installs everything into the (git-ignored) `macos/third/cef`. The first `pod install` therefore takes noticeably longer; subsequent runs are a no-op once the pinned version is present.

Requirements: `cmake` (and `ninja`, otherwise `make` is used) must be on `PATH` to build the wrapper — `brew install cmake ninja`.

> The wrapper is built `Debug` by default to match `flutter run` / `flutter build macos --debug`. For a release build set `CEF_WRAPPER_BUILD_TYPE=Release` before `pod install` (debug and release builds need a wrapper compiled in the matching configuration — `#if DCHECK_IS_ON()` changes its ABI).

#### Choosing the architecture

`WEBVIEW_CEF_MACOS_ARCH` selects which slices are prepared. It is read by both the download script and the podspec, so the CEF binaries and the `EXCLUDED_ARCHS` of your app always agree.

| Value | Result |
| --- | --- |
| `host` (default) | the build machine's architecture |
| `arm64` | Apple Silicon only |
| `x86_64` | Intel only |
| `universal` | both, merged with `lipo` |

```bash
WEBVIEW_CEF_MACOS_ARCH=universal pod install
cd .. && flutter build macos --release
```

A universal build downloads both CEF distributions and compiles the wrapper twice, so it takes about twice as long and needs roughly 8 GB of free scratch space. The framework binary, the ANGLE/SwiftShader dylibs beside it, `libcef_dll_wrapper.a`, and the helper executable are merged with `lipo`, then each is checked for the expected slices. Chromium's V8 startup snapshot is architecture specific (`v8_context_snapshot.<arch>.bin`), so both are copied into the framework's `Resources` and the right one is picked at runtime; the "Embed CEF Helpers" build phase fails the build if the helper does not cover every architecture the app is being built for. The selected value is recorded in `macos/third/cef/version.txt`, so changing it re-prepares `macos/third/cef` on the next `pod install`.

### Linux

```bash
flutter pub add webview_cef
```

CEF is downloaded automatically on the first build (x64 and arm64 supported). Make sure the usual Flutter Linux desktop toolchain is installed (`clang`, `cmake`, `ninja-build`, `libgtk-3-dev`, `pkg-config`).

---

## Quick start

```dart
import 'package:flutter/material.dart';
import 'package:webview_cef/webview_cef.dart';

class MyWebView extends StatefulWidget {
  const MyWebView({super.key});
  @override
  State<MyWebView> createState() => _MyWebViewState();
}

class _MyWebViewState extends State<MyWebView> {
  late final WebViewController _controller;

  @override
  void initState() {
    super.initState();
    _controller = WebviewManager().createWebView(
      loading: const Center(child: CircularProgressIndicator()),
    );
    _init();
  }

  Future<void> _init() async {
    await WebviewManager().initialize(); // call once for the whole app
    _controller.setWebviewListener(WebviewEventsListener(
      onUrlChanged: (url) => debugPrint('url => $url'),
      onLoadEnd: (controller, url) => debugPrint('loaded => $url'),
    ));
    await _controller.initialize('https://flutter.dev');
  }

  @override
  void dispose() {
    _controller.dispose();
    WebviewManager().quit(); // only when tearing down the whole app
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return ValueListenableBuilder<bool>(
      valueListenable: _controller,
      builder: (_, ready, __) =>
          ready ? _controller.webviewWidget : _controller.loadingWidget,
    );
  }
}
```

A full-featured example (navigation bar, cookies, JS bridge, DevTools) lives in [`example/`](example/).

---

## Usage

### Lifecycle

```dart
await WebviewManager().initialize(userAgent: 'my-app/1.0'); // once per app
final controller = WebviewManager().createWebView(loading: const Text('…'));
await controller.initialize('https://example.com');
// …
controller.dispose();
WebviewManager().quit(); // on app shutdown
```

### Navigation

```dart
controller.loadUrl('https://example.com');
controller.reload();
controller.goBack();
controller.goForward();
controller.openDevTools();
```

### Events

```dart
controller.setWebviewListener(WebviewEventsListener(
  onTitleChanged: (title) {},
  onUrlChanged: (url) {},
  onLoadStart: (controller, url) {},
  onLoadEnd: (controller, url) {},
  onConsoleMessage: (level, message, source, line) {},
));
```

### JavaScript bridge

```dart
// Dart -> JS
controller.executeJavaScript("document.title = 'set from Dart'");
final result = await controller.evaluateJavascript("1 + 1"); // "2"

// JS -> Dart
controller.setJavaScriptChannels({
  JavascriptChannel(
    name: 'Print',
    onMessageReceived: (msg) {
      debugPrint(msg.message);
      controller.sendJavaScriptChannelCallBack(
          false, "{'code':'200'}", msg.callbackId, msg.frameId);
    },
  ),
});
```

### Cookies

```dart
await WebviewManager().setCookie('example.com', 'key', 'value');
await WebviewManager().deleteCookie('example.com', 'key');
final all = await WebviewManager().visitAllCookies();
final some = await WebviewManager().visitUrlCookies('example.com', false);
```

### User-script injection

```dart
final scripts = InjectUserScripts()
  ..add(UserScript("console.log('at document start')", ScriptInjectTime.LOAD_START))
  ..add(UserScript("console.log('at document end')", ScriptInjectTime.LOAD_END));

final controller = WebviewManager().createWebView(injectUserScripts: scripts);
```

### eLinux 🐧

For eLinux, this plugin supports **Wayland** and **DRM-GBM** backends using a decoupled architecture that avoids GTK/X11 dependencies.

#### Runtime Dependencies

Ensure the target eLinux system has the following libraries installed:

- `libnss3`
- `libnspr4`
- `libfontconfig1`
- `libasound2`

#### CEF Binary Compatibility

- **Sandbox**: CEF's sandbox is disabled by default (`--no-sandbox`) to avoid SUID permission issues common on embedded filesystems.
- **Architecture**: While this project supports x64, ensure you have the correct CEF binaries for your target architecture (ARM64 support requires corresponding CEF builds).

#### Setup

1. Ensure your eLinux toolchain is correctly configured.
2. Use the `flutter-elinux` SDK to build your application.
3. The plugin will automatically use the `elinux/` port which implements an efficient pixel buffer rendering pipeline.

#### TO RUN

`cd example/`
`flutter-elinux pub get`
`flutter-elinux build elinux --release`

`./build/elinux/x64/release/bundle/webview_cef_example -b .`

---

## Windows build options

These CMake options can be set on the plugin target (defaults shown):

| Option | Default | Effect |
| --- | --- | --- |
| `WEBVIEW_CEF_GPU_TEXTURE` | `ON` | Zero-copy GPU rendering (CEF `OnAcceleratedPaint` → Flutter GPU surface texture). Set `OFF` to fall back to the software pixel-buffer path. |
| `WEBVIEW_CEF_USE_DEBUG_CEF` | `OFF` | Link/bundle the CEF **Debug** binaries even in Debug builds. By default Debug builds use the Release CEF binaries, because CEF's Debug DCHECKs crash off-screen rendering during IME. Turn `ON` only to step into CEF itself. |

## Updating CEF

The CEF/Chromium version is pinned in one place — `CEF_VERSION` in [`third/download.cmake`](third/download.cmake). Bump it to update CEF on all three platforms: Windows and Linux download it automatically, and macOS reads the same `CEF_VERSION` (via `macos/scripts/download_cef.sh`, run by the podspec's `prepare_command`) and re-downloads on the next `pod install` — no manual placement needed.

---

## Demo

<kbd>![demo](https://user-images.githubusercontent.com/7610615/190432410-c53ef1c4-33c2-461b-af29-b0ecab983579.gif)</kbd>

### Screenshots

| Windows | macOS | Linux |
| --- | --- | --- |
| <img src="https://user-images.githubusercontent.com/7610615/190431027-6824fac1-015d-4091-b034-dd58f79adbcb.png" width="400" /> | <img src="https://user-images.githubusercontent.com/7610615/190911381-db88cf33-70a2-4abc-9916-e563e54eb3f9.png" width="400" /> | <img src ="https://github.com/hlwhl/webview_cef/assets/49640121/50a4c2f6-1f24-4d10-9913-ad274d76cf3f" width="400" /> |
| <img src="https://user-images.githubusercontent.com/7610615/190431037-62ba0ea7-f7d1-4fca-8ce1-596a0a508f93.png" width="400" /> | <img src="https://user-images.githubusercontent.com/7610615/190911410-bd01e912-5482-4f9e-9dae-858874e5aaed.png" width="400" /> | <img src="https://github.com/hlwhl/webview_cef/assets/49640121/10a693d5-4ee0-4389-a1e8-1b0355f7c0a6" width="400" /> |

---

## Roadmap

- [x] Windows / macOS / Linux support
- [x] Multiple instances
- [x] JavaScript bridge & cookie management
- [x] IME support (Windows / macOS / Linux; tested with Chinese IMEs)
- [x] Mouse & trackpad input
- [x] DevTools
- [x] GPU zero-copy rendering & adaptive frame rate (Windows & macOS)
- [x] Easier macOS multi-process helper-bundle integration (one-line Podfile hook)
- [x] Universal (arm64 + x86_64) macOS builds
- [ ] Tear-free GPU sync (keyed-mutex) on Windows

Pull requests are welcome. Every PR runs build + `flutter analyze` CI on Windows, macOS, and Linux.

## Credits

Inspired by [**`flutter_webview_windows`**](https://github.com/jnschulze/flutter-webview-windows).

## License

[Apache License 2.0](LICENSE).

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