Android design
Parent page: Android
- Android Don't use X Window System.
- The part responsible for managing drawing on the screen is the Surface Manager in the C++ Native Libraries.
- Surface Manager: It is used for compositing window manager with off-screen buffering. Off-screen buffering means you cant directly draw into the screen, but your drawings go to the off-screen buffer. There it is combined with other drawings and form the final screen the user will see. This off screen buffer is the reason behind the transparency of windows.
##Android Graphics Subsystems
Canvas: Canvas is the Android class which application developers would use to draw widgets, pictures etc. In Android versions Froyo and Gingerbread Canvas would do the drawing using Skia. Android Honeycomb and onward, HWUI was added as an alternate GPU-accelerated option. Android Ice Cream Sandwich (ICS) and onward, HWUI is the default.
Skia: Skia is a 2D drawing API which is used by applications and works completely in software. For performance reasons Skia is slowly being replaced by HWUI.
HWUI The HWUI library enables UI components to be accelerated using the GPU. HWUI was introduced in Honeycomb to make the user interface fast, responsive and smooth. Since tablets had very high resolutions, using Skia for effects like animation would have been too CPU intensive and slow. HWUI requires an OpenGL ES 2.0 compliant GPU which cannot be emulated by software on Android.
Surface: A Surface in Android corresponds to an off screen buffer into which an application renders the contents. An application might be a game which uses OpenGL to draw 3D objects directly into a surface or a normal application which uses Skia to draw widgets, text, etc. It could even use HWUI library to enable a GPU accelerated user interface. From Android ICS, surfaces are implemented with a SurfaceTexture backend which means instead of a buffer, a texture is used.
##External links