This directory contains the modules related to hardware OpenGL ES emulation.
For now, this feature is experimental, and *nothing* will be built unless
you define BUILD_EMULATOR_OPENGL in your environment, for example with:
export BUILD_EMULATOR_OPENGL=true
You can also define the following to enable the "gralloc" module, which
corresponds to system-wide GLES emulation (by default, only a specific set
of applications are enabled, see below):
export BUILD_EMULATOR_OPENGL_DRIVER=true
I. Overview of components:
==========================
The 'emugen' tool is used to generate several source files related to the
EGL/GLES command stream used between the guest and the host during emulation.
host/tools/emugen -> emugen program
Note that emugen is capable of generating, from a single set of specification
files, three types of auto-generated sources:
- sources to encode commands into a byte stream.
- sources to decode the byte stream into commands.
- sources to wrap normal procedural EGL/GLES calls into context-aware ones.
Modules under the system/ directory corresponds to code that runs on the
guest, and implement the marshalling of EGL/GLES commands into a stream of
bytes sent to the host through a fast pipe mechanism.
system/GLESv1_enc -> encoder for GLES 1.1 commands
system/GLESv2_enc -> encoder for GLES 2.0 commands
system/renderControl_enc -> encoder for rendering control commands
system/egl -> emulator-specific guest EGL library
system/GLESv1 -> emulator-specific guest GLES 1.1 library
system/gralloc -> emulator-specific gralloc module
system/OpenglSystemCommon -> library of common routines
Modules under the host/ directory corresponds to code that runs on the
host, and implement the decoding of the command stream, translation of
EGL/GLES commands into desktop GL 2.0 ones, and rendering to an off-screen
buffer.
host/libs/GLESv1_dec -> decoder for GLES 1.1 commands
host/libs/GLESv2_dec -> decoder for GLES 2.0 commands
host/libs/renderControl_dec -> decoder for rendering control commands
host/libs/Translator/EGL -> translator for EGL commands
host/libs/Translator/GLES_CM -> translator for GLES 1.1 commands
host/libs/Translator/GLES_V2 -> translator for GLES 2.0 commands
host/libs/Translator/GLcommon -> library of common translation routines
host/libs/libOpenglRender -> rendering library (uses all host libs above)
can be used by the 'renderer' program below,
or directly linked into the emulator UI program.
host/renderer/ -> stand-alone renderer program executable.
this can run in head-less mode and receive requests from
several emulators at the same time. It is the receiving
end of all command streams.
Modules under the test/ directory correspond to test programs that are useful
to debug the various modules described above:
tests/EGL_host_wrapper -> a small library used to dynamically load the
desktop libEGL.so or a replacement named by the
ANDROID_EGL_LIB environment variable. This lib
provides all EGL entry points.
tests/emulator_test_renderer -> a small program to run the rendering library
in a single SDL window on the host desktop.
tests/gles_android_wrapper -> guest EGL / GLES libraries that are run on
the device to run some tests. Replace the
system/egl and system/GLESv1 modules for now.
tests/translator_tests/GLES_CM -> desktop GLESv1 translation unit test
tests/translator_tests/GLES_V2 -> desktop GLESv2 translation unit test
tests/translator_tests/MacCommon -> used by translation tests on Mac only.
tests/ut_rendercontrol_enc -> guest library used by tests/ut_renderer
tests/ut_rendercontrol_dec -> host library used by tests/ut_renderer
tests/ut_renderer -> unit-test for render control and rendering library.
II. Build system considerations:
--------------------------------
The dependencies on the more than 20 components described in the previous
section are pretty sophisticated, involving lots of auto-generated code and
non-trivial placement for guest/device libraries.
To simplify the development and maintenance of these modules, a set of
helper GNU Make function is defined in common.mk, and included from the
Android.mk in this directory.
These functions all begin with the "emugl-" prefix, and can be used to
declare modules, what information they export to other modules, or import
from them, and also what kind of auto-generated sources they depend on.
Look at the comments inside common.mk and the Android.mk of the modules
to better understand what's happening.
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