Window Compositor APIs (Compact 7)
3/12/2014
Window Compositor supports two graphics API libraries: graphics device interface (GDI) and OpenGL for Embedded Systems (OpenGL ES) 2.X. The system configuration determines the graphics API that Window Compositor uses to compose application back surfaces onto its own. Window Compositor does not affect the API that each application uses to display output. The system must still provide the driver that supports the graphics APIs that each application calls.
When Window Compositor uses the GDI APIs to update its back surface, it is using the GDI compositor. When Window Compositor uses the OpenGL ES APIs to update its back surface, it is using the OpenGL compositor. The compositor you decide to use depends on the features that you need for the device. The following table compares the features in the two compositors.
| GDI compositor | OpenGL compositor |
|---|---|
Provides software alpha blending when it is not available from the system hardware. |
Provides hardware alpha blending between system windows. |
Can use hardware-accelerated bit blitting (copying large blocks of pixels from one part of graphics memory to another). |
Can use hardware-accelerated bit blitting. |
Is better suited for devices without a graphics processing unit (GPU). |
Is better suited for devices with a GPU. |
Does not need hardware acceleration. |
Uses hardware acceleration to improve performance. |