Android WebView

1. Arch & Components

• Android WebView bases on Content API and Content View
• Different from Content API, it also depends on components originally from chrome browser, now in standalone modules, located in components/, including components of auto_login_parser, navigation_interception, visitedlink_browser, visitedlink_renderer and web_contents_delegate_android. These are useful for pages.
• No renderer process(in-process renderer) so no sandbox mechanism
• Graphics architecture is very different from content shell. It's still ongoing and expected to support software and hardware output.

2. API

• API is somewhat similar to EFL webview. No exposal about internal browser/renderer/gpu processes
• Capabilities to load URL and events or callbacks of page loading
• JavaScript API extension via addJavaScriptInterface. It allows JavaScript call to Java code, but reverse direction is not supported
• Kinds of APIs to provide page change notifications, callbacks for web pages

3. Message Loop & Events processing

• Integrate with Android Message handling by leveraging ContentView
• Native code sets timer into Message Loop of Java side

4. Graphics

• The rendering now is hardware acceleration by using chromium compositors.
• The output of compositor support software and hardware surface outputs.
• The architecture of hardware acceleration is different from others like content shell but it's like ChromeOS. Now it's in early stage, will use UberCompositor for software output.

5. WebAPI extension

• The API addJavaScriptInterface is for JavaScript API extension but only for the direction from JavaScript to Java code
• The reverse call direction(Java -> JavaScript) is not supported.
• addJavaScriptInterface is supported via NPObject mechanism which is previously used by NPAPI plugin. It supports out-of-process accessing though it's not needed in WebView now.
• Event notification from Java side seems not supported.

7. Details and Coverage of API

• WebViewClient for page changed notifications
• WebChromeClient for callbacks to participate in rendering logic
• Native Code/JS interaction
• Page loading
• Navigation & History
• Text Search
• Event handling
• Trackball, touch, keyboard
• No support for mouse event
• Settings: Encoding
• Page Info: Title, favicon
• HTTPS/SSL
• Page loading status, scale, redirects, override url, etc.

8. Source code

• src/android_webview
• libwebviewchromium.so and webviewchromium.pak are target of this module.
• Chromium developers work in progress to implement ChromeView based on android_webview module.
• ChromeView has the same APIs to Android Webview.
• https://github.com/pwnall/chromeview-src