externals: allow users to use system libenet (#7100)

externals/CMakeLists.txt

@@ -228,8 +228,14 @@ else()
 endif()
 
 # ENet
-add_subdirectory(enet)
+if(USE_SYSTEM_ENET)
-target_include_directories(enet INTERFACE ./enet/include)
+    find_package(libenet REQUIRED)
+    add_library(enet INTERFACE)
+    target_link_libraries(enet INTERFACE libenet::libenet)
+else()
+    add_subdirectory(enet)
+    target_include_directories(enet INTERFACE ./enet/include)
+endif()
 
 # Cubeb
 if (ENABLE_CUBEB)

externals/cmake-modules/CitraHandleSystemLibs.cmake

@@ -19,6 +19,7 @@ option(USE_SYSTEM_FDK_AAC_HEADERS "Use the system fdk-aac headers (instead of th
 option(USE_SYSTEM_FFMPEG_HEADERS "Use the system FFmpeg headers (instead of the bundled one)" OFF)
 option(USE_SYSTEM_GLSLANG "Use the system glslang and SPIR-V libraries (instead of the bundled ones)" OFF)
 option(USE_SYSTEM_ZSTD "Use the system Zstandard library (instead of the bundled one)" OFF)
+option(USE_SYSTEM_ENET "Use the system libenet (instead of the bundled one)" OFF)
 
 # Qt and MoltenVK are handled separately
 CMAKE_DEPENDENT_OPTION(DISABLE_SYSTEM_SDL2 "Disable system SDL2" OFF "USE_SYSTEM_LIBS" OFF)
@@ -37,6 +38,7 @@ CMAKE_DEPENDENT_OPTION(DISABLE_SYSTEM_FDK_AAC_HEADERS "Disable system fdk_aac" O
 CMAKE_DEPENDENT_OPTION(DISABLE_SYSTEM_FFMPEG_HEADERS "Disable system ffmpeg" OFF "USE_SYSTEM_LIBS" OFF)
 CMAKE_DEPENDENT_OPTION(DISABLE_SYSTEM_GLSLANG "Disable system glslang" OFF "USE_SYSTEM_LIBS" OFF)
 CMAKE_DEPENDENT_OPTION(DISABLE_SYSTEM_ZSTD "Disable system Zstandard" OFF "USE_SYSTEM_LIBS" OFF)
+CMAKE_DEPENDENT_OPTION(DISABLE_SYSTEM_ENET "Disable system libenet" OFF "USE_SYSTEM_LIBS" OFF)
 
 set(LIB_VAR_LIST
     SDL2
@@ -55,6 +57,7 @@ set(LIB_VAR_LIST
     FFMPEG_HEADERS
     GLSLANG
     ZSTD
+    ENET
     )
 
 # First, check that USE_SYSTEM_XXX is not used with USE_SYSTEM_LIBS

externals/cmake-modules/Findlibenet.cmake

@@ -0,0 +1,34 @@
+if(NOT libenet_FOUND)
+    pkg_check_modules(ENET_TMP libenet)
+
+    find_path(libenet_INCLUDE_DIRS NAMES enet.h PATH_SUFFIXES enet
+            PATHS
+            ${ENET_TMP_INCLUDE_DIRS}
+            /usr/include
+            /usr/local/include
+            )
+
+    find_library(libenet_LIBRARY_DIRS NAMES enet
+            PATHS
+            ${ENET_TMP_LIBRARY_DIRS}
+            /usr/lib
+            /usr/local/lib
+            )
+
+    if(libenet_INCLUDE_DIRS AND libenet_LIBRARY_DIRS)
+        set(libenet_FOUND TRUE CACHE INTERNAL "Found libenet")
+        message(STATUS "Found libenet ${libenet_LIBRARY_DIRS}, ${libenet_INCLUDE_DIRS}")
+    else()
+        set(libenet_FOUND FALSE CACHE INTERNAL "Found libenet")
+        message(STATUS "Libenet not found.")
+    endif()
+endif()
+
+if(libenet_FOUND AND NOT TARGET libenet::libenet)
+    add_library(libenet::libenet UNKNOWN IMPORTED)
+    set_target_properties(libenet::libenet PROPERTIES
+            INCLUDE_DIRECTORIES ${libenet_INCLUDE_DIRS}
+            INTERFACE_LINK_LIBRARIES ${libenet_LIBRARY_DIRS}
+            IMPORTED_LOCATION ${libenet_LIBRARY_DIRS}
+            )
+endif()