Logically, the Renderer calls the Driver APIs of the "DriverApi".
However, these Driver APIs are not executed immediately, but encoded as "Command"s which will be
decoded and executed in another thread "FEngine::loop".
Personally, I don't praise this design, since we benefit nothing from the encoding and decoding, but introduce
extra latency. And we are not able to tune the Vulkan APIs in a fine-grained way, for example, like rendering
the whole frame inside a single renderpass with multiple subpasses.
Besides, this design makes debugging more difficult, since we can't use the callstacks collected by the
RenderDoc to analyze the FrameGraph of the Renderer.
We can use the following code to modify the macros "DECL_DRIVER_API" and
"DECL_DRIVER_API_RETURN" inside the "CommandStream.h" to remove the encoding and decoding,
and thus the Driver APIs will be executed immediately.
#define DECL_DRIVER_API(methodName, paramsDecl, params) \
inline void methodName(paramsDecl) { \
DEBUG_COMMAND_BEGIN(methodName, false, params); \
AutoExecute callOnExit([=](){ \
DEBUG_COMMAND_END(methodName, true); \
}); \
using Cmd = COMMAND_TYPE(methodName); \
std::aligned_storage<sizeof(Cmd), alignof(Cmd)>::type p; \
CommandBase *base = new(&p) Cmd(mDispatcher->methodName##_, APPLY(std::move, params)); \
base->execute(*mDriver); \
}
#define DECL_DRIVER_API_RETURN(RetType, methodName, paramsDecl, params) \
inline RetType methodName(paramsDecl) { \
DEBUG_COMMAND_BEGIN(methodName, false, params); \
AutoExecute callOnExit([=](){ \
DEBUG_COMMAND_END(methodName, true); \
}); \
RetType result = mDriver->methodName##S(); \
using Cmd = COMMAND_TYPE(methodName##R); \
std::aligned_storage<sizeof(Cmd), alignof(Cmd)>::type p; \
CommandBase *base = new(&p) Cmd(mDispatcher->methodName##_, RetType(result), APPLY(std::move, params)); \
base->execute(*mDriver); \
return result; \
}