Android graphic architecture implementation analysis summary

 

Android graphic Architecture Analysis Summary

The implementation scheme mainly includes the following key points:

1


, Direct

Framebuffer


And

Framebuffer


Dual-Cache Technology

Without the use of solutions such as x-server, you can directly operate framebuffer to reduce the communication overhead caused by X-server. Open framebuffer and create two buffers (one is on screen front buffer and the other is back buffer, which may be in offscreen framebuffer or system memory ). In the source code, swapbuffers copies the back buffer content to the front buffer. The dual-cache technology allows you to draw in the back buffer, and then copy it to the front buffer for merging and display.

2


, Make full use

OpenGL


Graphical interface and hardware acceleration

Pass
OpenGL

Of
API

,
Android

High-performance
3D

Image.

OpenGL


Of

EGL


Interface, yes

OpenGL
Es



And underlying


Native




Interfaces between platform Windows systems.

 

3


Image Display cropping and local refresh

Multiple

Layer


Is defined as a layer vector.

Layervector


It contains all

Surface


Corresponding

Layer


,

Surfaceflinger


Based on each

Layer


Of

Z-order


Combine multiple layers into one that is finally displayed on the screen

Buffer


.

Z-order


:

Z



Order actually defines the cascade order between windows. Speaking of"

Z



The name is relative to the screen coordinate. Generally, all windows on the screen have a coordinate system, that is, the origin is in the upper left corner,

X



Axis horizontal to the right,

Y



Coordinates of the vertical and downward axes.

Z



The order is relative to a hypothetical


Z



For the axis, this


Z



The axis points out of the screen. The window is in this


Z



The value on the axis determines its


Z



.

Z



Window with a large order value, Overwrite


Z



Window with a small order value.

In the layer vector, each layer corresponds to

Z


Order value. At the same time, you can set the priority for the layer so that some layers can achieve front-end display. Finally, you can use the corresponding cropping algorithm to calculate the area that can be displayed.

Optimized re-painting mechanism: the local refresh mechanism is adopted, not every time

Repaint


The entire screen needs to be re-painted. First, the area to be re-painted (

Minvalidregion


), If

Displayhardware: update_on_demand


You can set the border of the area to be repainted to perform partial re-painting.

 

4


Easy-to-use graphic primitives, event mechanisms, and controls

Android. Graphics,
Android. View

And
Android. widget

Functions and other similar graphics libraries such
QT/GTK +

Provides basic graphic primitives (such as drawing points and draw lines, setting graphical context), event mechanisms, and controls for developing graphical user interfaces.

 

5


And powerful functions

2d


Graphics engine Library

Skia

Yes

2d


Vector graphics processing function library, including fonts, coordinate transformations, and bitmaps, all of which are efficient and concise. It encapsulates the underlying graphics hardware and provides the most basic graphic hardware primitive for the above graphics library. Not only

Google
Chrome

Browser,
Skia

Processing as a drawing, matching
OpenGL/es


Enhance the display effect with specific hardware features.