合成类型

frameworks/native/services/surfaceflinger./DisplayHardware/HWComposer.cpp

"GLES",

"HWC",

"BACKGROUND",

"FB TARGET",

"UNKNOWN



hardware/libhardware/include/hardware/hwcomposer_defs.h

enum {

/* this layer is to be drawn into the framebuffer by SurfaceFlinger */

HWC_FRAMEBUFFER = 0,

/* this layer will be handled in the HWC */

HWC_OVERLAY = 1,

/* this is the background layer. it's used to set the background color.

* there is only a single background layer */

HWC_BACKGROUND = 2,

/* this layer holds the result of compositing the HWC_FRAMEBUFFER layers.

* Added in HWC_DEVICE_API_VERSION_1_1. */

HWC_FRAMEBUFFER_TARGET = 3,

};