The document discusses the history and architecture of Android's WebView. It describes how WebView has transitioned from using a custom WebKit implementation to being based on the Chromium rendering engine. It also summarizes the threading models of Chrome and WebView and explains how rendering occurs in two phases of painting and compositing layers.

1. *
Android Chromium WebView

2. WebView version history
Android <= J: custom WebKit-based “classic” WebView
Android K: Chromium 30/33-based WebView
Android L: Unbundled evergreen WebView, autoupdated via
Play Services

3. Organization of code
android.webkit.WebView
WebViewProvider
Chromium source tree
AwContents
ContentViewCore
“glue layer”
Android source tree
Rendering engine
MyWebViewApp
Android framework
android_webview/
Chromium content layer

4. How Rendering Work

5. rendering occurs in two phases: paint,
composite.
 painting is the population of layers’ backings (bitmaps with
software rasterization; textures in hardware rasterization).
 drawing is the compositor combining layers into the final
screen image;

6. 渲染过程

9. Threading model summary
Chrome
Multi-process
 UI thread
 GPU thread
 Texture upload thread
 Per renderer process:
o Blink thread
o CC impl thread
o Raster thread
WebView
Single-process
 Combined UI + renderer CC
thread
 Android RenderThread (+in-
process GPU thread)
 Canvas/WebGL GPU thread
 Blink thread
 Raster thread

11. Blink进展
 Binding Team
 Layout Team
 Memory Team。BlinkAllocator；Oilpan（Oilpan is a
project to replace reference counting in Blink with a GC）
 Paint Team。Slimming Paint (Redesigning Painting and
Compositing)

12.  Style Team
 Web Components Team
 Animation Team

13. 结论
 UI线程很忙。IO操作、cpu密集操作不要放在UI线程执行，
开发中尽量减轻UI的负担。
 WebView有内存泄漏的问题。
 硬件加速速度更快，但消耗更多内存，开发中需要考虑性能
和内存的平衡。
 WebView放在单独的进程运行。
 WebView的性能在不断提高。

14.  https://www.chromium.org/developers/design-documents
 http://www.ituring.com.cn/minibook/705
 http://blog.csdn.net/hongbomin?viewmode=contents
 http://blog.csdn.net/Luoshengyang