Re-add libretro core

CMakeLists.txt

@@ -24,6 +24,7 @@ set(CMAKE_OSX_DEPLOYMENT_TARGET "10.14.0" CACHE STRING "")
 if(NOT ANDROID)
   option(BUILD_NOGUI_FRONTEND "Build the NoGUI frontend" ON)
   option(BUILD_QT_FRONTEND "Build the Qt frontend" ON)
+  option(BUILD_LIBRETRO_CORE "Build a libretro core" OFF)
   option(ENABLE_DISCORD_PRESENCE "Build with Discord Rich Presence support" ON)
   option(ENABLE_CHEEVOS "Build with RetroAchievements support" ON)
   option(USE_SDL2 "Link with SDL2 for controller support" ON)
@@ -40,7 +41,7 @@ endif()
 if((LINUX OR FREEBSD) OR ANDROID)
   option(USE_EGL "Support EGL OpenGL context creation" ON)
 endif()
-if((LINUX OR FREEBSD) AND NOT ANDROID)
+if((LINUX OR FREEBSD) AND NOT ANDROID AND NOT BUILD_LIBRETRO_CORE)
   option(USE_DRMKMS "Support DRM/KMS OpenGL contexts" OFF)
   option(USE_FBDEV "Support FBDev OpenGL contexts" OFF)
   option(USE_EVDEV "Support EVDev controller interface" ON)
@@ -80,6 +81,40 @@ if(ANDROID)
 endif()
 
 
+# Disable platform integration when building for libretro.
+if(BUILD_LIBRETRO_CORE)
+  message("Building libretro core, disabling platform integration.")
+
+  if(USE_EGL)
+    set(USE_EGL OFF)
+  endif()
+  if(BUILD_NOGUI_FRONTEND)
+    set(BUILD_NOGUI_FRONTEND OFF)
+  endif()
+  if(BUILD_QT_FRONTEND)
+    set(BUILD_QT_FRONTEND OFF)
+  endif()
+  if(ENABLE_DISCORD_PRESENCE)
+    set(ENABLE_DISCORD_PRESENCE OFF)
+  endif()
+  if(ENABLE_CHEEVOS)
+    set(ENABLE_CHEEVOS OFF)
+  endif()
+  if(USE_SDL2)
+    set(USE_SDL2 OFF)
+  endif()
+  if(USE_X11)
+    set(USE_X11 OFF)
+  endif()
+  if(USE_WAYLAND)
+    set(USE_WAYLAND OFF)
+  endif()
+
+  # Force PIC when compiling a libretro core.
+  set(CMAKE_POSITION_INDEPENDENT_CODE ON)
+endif()
+
+
 # Common include/library directories on Windows.
 if(WIN32 AND USE_SDL2)
   set(SDL2_FOUND TRUE)
@@ -235,7 +270,7 @@ endif()
 
 
 # Write binaries to a seperate directory.
-if(WIN32)
+if(WIN32 AND NOT BUILD_LIBRETRO_CORE)
   # For Windows, use the source directory, except for libretro.
   set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/bin/${CPU_ARCH}")
 else()
@@ -263,6 +298,6 @@ enable_testing()
 add_subdirectory(dep)
 add_subdirectory(src)
 
-if(ANDROID)
+if(ANDROID AND NOT BUILD_LIBRETRO_CORE)
   add_subdirectory(android/app/src/cpp)
 endif()

dep/CMakeLists.txt

@@ -27,6 +27,10 @@ if(ENABLE_CHEEVOS)
   add_subdirectory(rcheevos)
 endif()
 
+if(BUILD_LIBRETRO_CORE)
+  add_subdirectory(libretro-common)
+endif()
+
 if(${CPU_ARCH} STREQUAL "aarch32" OR ${CPU_ARCH} STREQUAL "aarch64")
   add_subdirectory(vixl)
 endif()

src/CMakeLists.txt

@@ -1,10 +1,16 @@
+if(BUILD_LIBRETRO_CORE)
+  add_definitions("-DLIBRETRO=1")
+endif()
+
 add_subdirectory(common)
 add_subdirectory(core)
 add_subdirectory(scmversion)
 
-add_subdirectory(common-tests)
-if(WIN32)
-  add_subdirectory(updater)
+if(NOT BUILD_LIBRETRO_CORE)
+  add_subdirectory(common-tests)
+  if(WIN32)
+    add_subdirectory(updater)
+  endif()
 endif()
 
 add_subdirectory(frontend-common)
@@ -16,3 +22,8 @@ endif()
 if(BUILD_QT_FRONTEND)
   add_subdirectory(duckstation-qt)
 endif()
+
+if(BUILD_LIBRETRO_CORE)
+  add_subdirectory(duckstation-libretro)
+endif()
+

src/common/CMakeLists.txt

@@ -222,6 +222,9 @@ endif()
 if(APPLE)
   # Needed for Vulkan Swap Chain.
   target_link_libraries(common PRIVATE "objc")
+endif()
+
+if(APPLE AND NOT BUILD_LIBRETRO_CORE)
   target_sources(common PRIVATE
     gl/context_agl.mm
     gl/context_agl.h

src/common/vulkan/shader_compiler.cpp

@@ -124,7 +124,9 @@ bool InitializeGlslang()
     return false;
   }
 
+#ifndef LIBRETRO
   std::atexit([]() { glslang::FinalizeProcess(); });
+#endif
 
   glslang_initialized = true;
   return true;

src/common/window_info.h

@@ -13,6 +13,7 @@ struct WindowInfo
     MacOS,
     Android,
     Display,
+    Libretro,
   };
 
   enum class SurfaceFormat