add libretro platform

CMakeLists.txt

@@ -45,6 +45,8 @@ if(AUDIO_BACKEND STREQUAL "")
         set(AUDIO_BACKEND "openal")
     elseif(PLATFORM STREQUAL "ps2")
         set(AUDIO_BACKEND "ps2")
+    elseif(PLATFORM STREQUAL "libretro")
+        set(AUDIO_BACKEND "miniaudio")
     else()
         set(AUDIO_BACKEND "miniaudio")
     endif()
@@ -104,6 +106,8 @@ file(GLOB PLATFORM_SOURCES src/${PLATFORM}/*.c)
 
 if(PLATFORM STREQUAL "android")
     add_library(butterscotch SHARED ${SOURCES} ${PLATFORM_SOURCES} ${AUDIO_SOURCES})
+elseif(PLATFORM STREQUAL "libretro")
+    add_library(butterscotch MODULE ${SOURCES} ${PLATFORM_SOURCES} ${AUDIO_SOURCES})
 else()
     add_executable(butterscotch ${SOURCES} ${PLATFORM_SOURCES} ${AUDIO_SOURCES})
 endif()
@@ -684,6 +688,90 @@ elseif(PLATFORM STREQUAL "ps3")
     # mojoal calls SDL atomics/threads, so SDL2 must link after it (static link order)
     target_link_libraries(mojoal PUBLIC ${SDL2_LIBRARIES})
     target_link_libraries(butterscotch PRIVATE ${SDL2_LIBRARIES} m gcm_sys rsx sysutil io audio rt lv2 io audio bzip2 stb_ds sha1 ps3gl mojoal stb_vorbis)
+elseif(PLATFORM STREQUAL "libretro")
+    # bzip2 needs -fPIC for linking into shared library
+    set_target_properties(bzip2 PROPERTIES POSITION_INDEPENDENT_CODE ON)
+    set_target_properties(sha1 PROPERTIES POSITION_INDEPENDENT_CODE ON)
+
+    if(ENABLE_SW_RENDERER)
+        target_sources(butterscotch PRIVATE
+            src/sw/sw_renderer.c
+            src/desktop/stb_impl.c
+        )
+        target_include_directories(butterscotch PRIVATE
+            ${CMAKE_SOURCE_DIR}/src/sw
+        )
+    else()
+        target_sources(butterscotch PRIVATE
+            src/gl/gl_renderer.c
+            src/gl_common/gl_common.c
+            src/libretro/libretro-common/glsm/glsm.c
+            src/libretro/libretro-common/glsym/rglgen.c
+        )
+
+        if(USING_GLES)
+            target_sources(butterscotch PRIVATE src/libretro/libretro-common/glsym/glsym_es3.c)
+            target_compile_definitions(butterscotch PRIVATE HAVE_OPENGLES HAVE_OPENGLES3)
+            find_library(GLES2_LIB GLESv2)
+            target_link_libraries(butterscotch PRIVATE ${GLES2_LIB})
+            target_compile_definitions(butterscotch PRIVATE GLclampd=GLclampf)
+        else()
+            target_sources(butterscotch PRIVATE src/libretro/libretro-common/glsym/glsym_gl.c)
+            target_compile_definitions(butterscotch PRIVATE HAVE_OPENGL)
+            find_package(OpenGL REQUIRED)
+            target_link_libraries(butterscotch PRIVATE OpenGL::GL)
+        endif()
+
+        set_source_files_properties(
+            src/libretro/libretro-common/glsm/glsm.c
+            PROPERTIES COMPILE_OPTIONS "-w"
+        )
+        target_include_directories(butterscotch PRIVATE
+            ${CMAKE_SOURCE_DIR}/src/gl
+            ${CMAKE_SOURCE_DIR}/src/gl_common
+        )
+
+    endif()
+    target_sources(butterscotch PRIVATE
+        src/image/image_decoder.c
+        src/desktop/stb_impl.c
+    )
+
+    target_include_directories(butterscotch PRIVATE
+        ${CMAKE_SOURCE_DIR}/src/image
+        ${CMAKE_SOURCE_DIR}/src/desktop
+        ${CMAKE_SOURCE_DIR}/src/libretro
+        ${CMAKE_SOURCE_DIR}/src/libretro/libretro-common/include
+        vendor/stb/image
+        vendor/stb/vorbis
+    )
+
+    # Rename output to butterscotch_libretro.so
+    set_target_properties(butterscotch PROPERTIES
+        PREFIX ""
+        OUTPUT_NAME "butterscotch_libretro"
+    )
+
+    # Version script for symbol visibility
+    target_link_options(butterscotch PRIVATE
+        -Wl,--version-script=${CMAKE_SOURCE_DIR}/src/libretro/link.T
+        -Wl,--no-undefined
+    )
+
+    # Libraries
+    find_library(DL_LIB dl)
+    find_library(ATOMIC_LIB atomic)
+
+    target_link_libraries(butterscotch PRIVATE bzip2 stb_ds sha1 m ${DL_LIB} ${AUDIO_LIBRARIES})
+    if(ATOMIC_LIB)
+        target_link_libraries(butterscotch PRIVATE ${ATOMIC_LIB})
+    endif()
+
+    target_compile_definitions(butterscotch PRIVATE
+        _GNU_SOURCE
+        _FILE_OFFSET_BITS=64
+        HAVE_LIBRETRO
+    )
 else()
     message(FATAL_ERROR "Unknown platform! ${PLATFORM}")
 endif()

src/gl/gl_renderer.c

@@ -52,7 +52,7 @@ static const char* baseFragmentShader =
 // ===[ Runtime OpenGL extension checks ]===
 
 static bool hasFBO() {
-#if !defined(__EMSCRIPTEN__) && !defined(__ANDROID__)
+#if !defined(__EMSCRIPTEN__) && !defined(__ANDROID__) && !defined(HAVE_LIBRETRO)
     return glGenFramebuffers;
 #else
     return true;
@@ -279,7 +279,7 @@ static void glInit(Renderer* renderer, DataWin* dataWin) {
         abort();
     }
 
-#if !defined(__EMSCRIPTEN__) && !defined(__ANDROID__)
+#if !defined(__EMSCRIPTEN__) && !defined(__ANDROID__) && !defined(HAVE_LIBRETRO)
     gl_init_wrappers();
 #endif
 

src/gl_common/gl_wrappers.h

@@ -1,4 +1,4 @@
-#if !defined(_BS_GL_WRAPPERS_H_) && !defined(__EMSCRIPTEN__) && !defined(PLATFORM_PS3) && !defined(__ANDROID__)
+#if !defined(_BS_GL_WRAPPERS_H_) && !defined(__EMSCRIPTEN__) && !defined(PLATFORM_PS3) && !defined(__ANDROID__) && !defined(HAVE_LIBRETRO)
 #define _BS_GL_WRAPPERS_H_
 
 static inline void gl_init_wrappers(void) {

src/libretro/glad/glad.h

@@ -0,0 +1,7 @@
+#include <glsm/glsmsym.h>
+#define glDeleteFramebuffersEXT glDeleteFramebuffers
+#define glFramebufferTexture2DEXT glFramebufferTexture2D
+#define glBindFramebufferEXT glBindFramebuffer
+#define glGenFramebuffersEXT glGenFramebuffers
+#define glDeleteVertexArraysOES glDeleteVertexArrays
+#define glGenVertexArraysOES glGenVertexArrays