52 lines
2.3 KiB
Plaintext
52 lines
2.3 KiB
Plaintext
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Design of the GLES Tracing Library
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Code Runtime Behavior:
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Initialization:
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egl_display_t::initialize() calls initEglTraceLevel() to figure out whether tracing should be
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enabled. Currently, the shell properties "debug.egl.trace" and "debug.egl.debug_proc" together
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control whether tracing should be enabled for a certain process. If tracing is enabled, this
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calls GLTrace_start() to start the trace server.
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Note that initEglTraceLevel() is also called from early_egl_init(), but that happens in the
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context of the zygote, so that invocation has no effect.
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egl_display_t::initialize() then calls setGLHooksThreadSpecific() where we set the thread
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specific gl_hooks structure to point to the trace implementation. From this point on, every
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GLES call is redirected to the trace implementation.
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Application runtime:
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While the application is running, all its GLES calls are directly routed to their corresponding
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trace implementation.
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For EGL calls, the trace library provides a bunch of functions that must be explicitly called
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from the EGL library. These functions are declared in glestrace.h
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Application shutdown:
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Currently, the application is killed when the user stops tracing from the frontend GUI. We need
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to explore if a more graceful method of stopping the application, or detaching tracing from the
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application is required.
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Code Structure:
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glestrace.h declares all the hooks exposed by libglestrace. These are used by EGL/egl.cpp and
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EGL/eglApi.cpp to initialize the trace library, and to inform the library of EGL calls.
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All GL calls are present in GLES_Trace/src/gltrace_api.cpp. This file is generated by the
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GLES_Trace/src/genapi.py script. The structure of all the functions looks like this:
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void GLTrace_glFunction(args) {
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// declare a protobuf
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// copy arguments into the protobuf
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// call the original GLES function
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// if there is a return value, save it into the protobuf
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// fixup the protobuf if necessary
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// transport the protobuf to the host
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}
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The fixupGLMessage() call does any custom processing of the protobuf based on the GLES call.
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This typically amounts to copying the data corresponding to input or output pointers.
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