Remove version checks for std::filesystem::path - instead, just check…

… that it's actually usable

- rename to `HAS_STD_FILESYSTEM_PATH` for clarity
- centralize WIN32 check
- this was actually failing on windows due to the lack of `/Zc:__cplusplus` - it's not great that CMake only allows specifying flags for `check_cxx_source_compiles()` via CMAKE_CXX_FLAGS though

refs #9

StreamDeckSDK/CMakeLists.txt

@@ -31,14 +31,20 @@ target_link_libraries(
   websocketpp
 )
 
-# ghc::filesystem only supports UTF-8 locales, which is not common on Windows.
-# In lieu of all callers properly using UTF-8 locales, we just require
-# std::filesystem.
-if ((NOT WIN32) AND HAS_STD_FILESYSTEM)
-  target_compile_definitions(StreamDeckSDK PUBLIC ESD_HAS_STD_FILESYSTEM)
+# Older MacOS SDKs (currently targeting v10.11) claim C++20 support, but do not
+# have a usable `std::filesystem`; use a polyfill.
+#
+# Don't use it everywhere as ghc::filesystem only supports UTF-8 locales,
+# which are not common on Windows.
+#
+# Don't require that callers explicitly convert from the actual locale to UTF-8;
+# instead, use `std::filesystem` where available.
+if (HAS_STD_FILESYSTEM_PATH)
+  target_compile_definitions(StreamDeckSDK PUBLIC ESD_HAS_STD_FILESYSTEM_PATH)
 else()
   target_link_libraries(StreamDeckSDK PUBLIC ghc_filesystem)
 endif()
+
 if (NOT MSVC)
   target_link_libraries(StreamDeckSDK PUBLIC fmt)
 endif()

StreamDeckSDK/ESDFilesystem.cpp

@@ -2,6 +2,6 @@
 // This source code is licensed under the MIT-style license found in
 // the LICENSE file.
 
-#ifndef ESD_HAS_STD_FILESYSTEM
+#ifndef ESD_HAS_STD_FILESYSTEM_PATH
 #include <ghc/fs_impl.hpp>
 #endif

StreamDeckSDK/ESDFilesystem.h

@@ -5,7 +5,7 @@
 
 /* Use std::filesystem where available, ghc::filesystem otherwise. */
 
-#ifdef ESD_HAS_STD_FILESYSTEM
+#ifdef ESD_HAS_STD_FILESYSTEM_PATH
 #include <filesystem>
 namespace ESD {
   namespace filesystem {

Vendor/filesystem.cmake

@@ -1,21 +1,23 @@
 include(FetchContent)
 include(CheckCXXSourceCompiles)
 
+if(MSVC)
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /std:c++20 /Zc:__cplusplus")
+endif()
+
 check_cxx_source_compiles("
-#ifdef __APPLE__
-#include <Availability.h> // for deployment target to support pre-catalina targets without std::fs
-#endif
-#if ((defined(_MSVC_LANG) && _MSVC_LANG >= 201703L) || (defined(__cplusplus) && __cplusplus >= 201703L)) && defined(__has_include)
-#if __has_include(<filesystem>) && (!defined(__MAC_OS_X_VERSION_MIN_REQUIRED) || __MAC_OS_X_VERSION_MIN_REQUIRED >= 101500)
-#define GHC_USE_STD_FS
-#endif
-#endif
-#ifndef GHC_USE_STD_FS
-#error \"std::filesystem missing or unusable\"
-#endif
-" HAS_STD_FILESYSTEM)
+#include <filesystem>
+
+int main() {
+  std::filesystem::path path;
+  return 0;
+}
+" HAS_STD_FILESYSTEM_PATH)
 
-if(NOT HAS_STD_FILESYSTEM)
+if(NOT HAS_STD_FILESYSTEM_PATH)
+  if(WIN32)
+    message(FATAL_ERROR "Refusing to use `ghc::filesystem` on Windows due to differing locale behavior")
+  endif()
   FetchContent_Declare(
     filesystem
     URL https://github.com/gulrak/filesystem/archive/refs/tags/v1.5.12.zip