feat: make some sound on linux, power by sdl3 (#5)

.gitmodules

@@ -1,3 +1,6 @@
 [submodule "third_party/mdspan"]
 	path = third_party/mdspan
 	url = git@github.com:kokkos/mdspan.git
+[submodule "third_party/SDL"]
+	path = third_party/SDL
+	url = git@github.com:libsdl-org/SDL.git

CMakeLists.txt

@@ -1,5 +1,6 @@
 # libstdaudio
 # Copyright (c) 2018 - Timur Doumler
+# Copyright (c) 2023 - Lan Zongwei
 # Distributed under the Boost Software License, Version 1.0.
 # (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
 
@@ -15,6 +16,20 @@ set(CMAKE_CXX_STANDARD 23)
 
 option(AUDIO_ENABLE_TESTS "Enable tests." ON)
 option(AUDIO_ENABLE_EXAMPLES "Build examples." ON)
+option(AUDIO_WITH_SDL3 "Enable SDL backend." ON)
+option(AUDIO_STATIC "Use static libraries" OFF)
+
+find_package(Git QUIET)
+
+if(GIT_FOUND AND EXISTS "${PROJECT_SOURCE_DIR}/.git")
+    execute_process(COMMAND ${GIT_EXECUTABLE} submodule update --init --recursive
+                    WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+                    RESULT_VARIABLE GIT_SUBMOD_RESULT)
+    if(NOT GIT_SUBMOD_RESULT EQUAL "0")
+        message(FATAL_ERROR "git submodule update --init --recursive\
+ failed with ${GIT_SUBMOD_RESULT}, please checkout submodules")
+    endif()
+endif()
 
 if (MSVC)
 	set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /W4 /WX")
@@ -31,6 +46,41 @@ if (NOT MDSPAN_EXIST)
   add_subdirectory(third_party/mdspan)
 endif()
 
+find_package(PkgConfig)
+
+if (AUDIO_WITH_SDL3)
+  pkg_search_module(SDL3 sdl3)
+
+  add_compile_definitions(AUDIO_USE_SDL3 DEBUG_AUDIO)
+
+  if (SDL3_FOUND)
+    message(STATUS "System SDL3 found.")
+  else()
+    message(STATUS "Use internal SDL3.")
+
+    # Disable all subsystems except Audio, Events, Threads, and loadso(for shared library)
+    set(SDL_SUBSYSTEMS
+        Atomic Video Render Joystick Haptic Hidapi Power Timers
+        File CPUinfo Filesystem Sensor Locale Misc)
+    foreach(_SUB ${SDL_SUBSYSTEMS})
+      string(TOUPPER ${_SUB} _OPT)
+      set(SDL_${_OPT} OFF CACHE BOOL "Enable the ${_SUB} subsystem" FORCE)
+    endforeach()
+
+    if (AUDIO_STATIC)
+      set(SDL_STATIC ON CACHE BOOL "Build a static version of SDL" FORCE)
+      set(SDL_LOADSO OFF CACHE BOOL "Enable the LOADSO subsystem" FORCE)
+
+      foreach(AUDIO_LIB ALSA JACK PIPEWIRE PULSEAUDIO SNDIO)
+        set(SDL_${AUDIO_LIB}_SHARED OFF CACHE BOOL "Dynamically load ${AUDIO_LIB} audio support" FORCE)
+      endforeach()
+    endif()
+
+    set(SDL_DISABLE_INSTALL OFF CACHE BOOL "Disable installation of SDL3" FORCE)
+    add_subdirectory(third_party/SDL)
+  endif()
+endif()
+
 add_library(audio INTERFACE)
 add_library(std::audio ALIAS audio)
 target_include_directories(audio INTERFACE
@@ -39,6 +89,14 @@ target_include_directories(audio INTERFACE
 )
 target_link_libraries(audio INTERFACE std::mdspan)
 
+if (AUDIO_WITH_SDL3)
+  if (AUDIO_STATIC)
+    target_link_libraries(audio INTERFACE SDL3::SDL3-static)
+  else()
+    target_link_libraries(audio INTERFACE SDL3::SDL3)
+  endif()
+endif()
+
 ###################################################
 
 install(TARGETS audio EXPORT audioTargets

README.md

@@ -15,17 +15,43 @@ Personally, I think this proposal wouldn't accept recently, but I really like an
 
 Basically, this repo's custom backend is a P1386-like SLD3 C++ wrapper. So, may not send pr to upstream. Because it is no longer a header-only library. (except the proposal owner accepts that)
 
-Unlike the [original repo](https://github.com/stdcpp-audio/libstdaudio), I decide to flollow the API design presented in P1386 try my best.
-So you can use it since you already read P1386.
+<del>Unlike the [original repo](https://github.com/stdcpp-audio/libstdaudio), I decide to flollow the API design presented in P1386 try my best.
+So you can use it since you already read P1386.</del> I found P1386 is not so suitable to wrapper SDL, so I decide to make some change base on P1386.
 
-Here are some stuffs different with the [original repo](https://github.com/stdcpp-audio/libstdaudio).
+Here are some stuffs different with the [original repo](https://github.com/stdcpp-audio/libstdaudio) and P1386.
 
 1. use mdspan for contiguous data view, and `std::span` vector for distant view.
 
 2. add multidimensional subscript operation since it supported by compiler.
 
 3. access operator's argument is `(channel, frame)` instead of `(frame, channel)`, which follow P1386.
 
+4. if any error happen, a `std::runtime_error` will be throw, is in the feature, exception is not suitable, another `try_xxx` api will be add, which use `std::expected` as return type.
+
+5. sdl backend API changes:
+
+```
+class audio_device:
+
+modify:
+bool start(AudioDeviceCallback auto&& startCallback = no_op,
+    AudioDeviceCallback auto&& stopCallback = no_op);
+=>
+bool start();
+
+just play the audio device.
+
+add:
+bool pause();
+
+Pause the audio device.
+
+bool set_sample_type();
+
+Set undering sample type, return false if device is running.
+
+```
+
 ## Repository structure
 
 `include` contains the `audio` header, which is the only header users of the library should include. It also contains the header files of the different classes and functions, prefixed with `__audio_`. Please refer to these header files for a documentation of the API as implemented here. (We plan to set up proper documentation soon.)

include/experimental/__p1386/audio_buffer.h

@@ -152,7 +152,6 @@ template <typename SampleType> class audio_buffer {
   std::variant<contiguous_view_type, distant_view_type> _data_view;
 };
 
-// TODO: this is currently macOS specific!
 using audio_clock_t = chrono::steady_clock;
 
 template <typename SampleType> struct audio_device_io {

include/experimental/audio

@@ -10,7 +10,9 @@
 #include "experimental/__p1386/audio_device.h"
 #include "experimental/__p1386/audio_event.h"
 
-#ifdef __APPLE__
+#if defined(AUDIO_USE_SDL3)
+  #include "experimental/audio_backend/sdl_backend.h"
+#elif defined(__APPLE__)
   #include "experimental/audio_backend/__coreaudio_backend.h"
 #elif defined(_WIN32)
   #include "experimental/audio_backend/__wasapi_backend.h"