Use swl-variant to improve compile times.

.gitmodules

@@ -6,4 +6,8 @@
 	url = https://github.com/htacg/tidy-html5.git
 [submodule "native~/extern/enum-flags"]
 	path = native~/extern/enum-flags
-	url = https://github.com/grisumbras/enum-flags.git
+	url = https://github.com/kring/enum-flags.git
+[submodule "native~/extern/swl-variant"]
+	path = native~/extern/swl-variant
+	url = https://github.com/kring/swl-variant.git
+	branch = exception-public-inheritance

native~/CMakeLists.txt

@@ -87,6 +87,7 @@ if (NOT IOS)
     set(CESIUM_INSTALL_STATIC_LIBS OFF)
 endif()
 
+add_subdirectory(extern/swl-variant)
 add_subdirectory(extern/cesium-native)
 
 # Don't build the cesium-native tests by default.
@@ -106,69 +107,6 @@ set(LIB_INSTALL_DIR ${CMAKE_INSTALL_LIBDIR})
 
 # Specify all targets that need to compile bitcode
 if (${CMAKE_SYSTEM_NAME} STREQUAL "iOS")
-    # set (ALL_TARGETS
-    #     CesiumForUnityNative-Runtime
-    #     Async++
-    #     Cesium3DTilesContent
-    #     Cesium3DTilesReader
-    #     Cesium3DTilesSelection
-    #     CesiumAsync
-    #     CesiumGeometry
-    #     CesiumGeospatial
-    #     CesiumGltf
-    #     CesiumGltfContent
-    #     CesiumGltfReader
-    #     CesiumJsonReader
-    #     CesiumRasterOverlays
-    #     CesiumQuantizedMeshTerrain
-    #     CesiumUtility
-    #     draco_attributes
-    #     draco_compression_attributes_dec
-    #     draco_compression_bit_coders
-    #     draco_compression_entropy
-    #     draco_compression_decode
-    #     draco_compression_mesh_dec
-    #     draco_compression_point_cloud_dec
-    #     draco_core
-    #     draco_mesh
-    #     draco_metadata
-    #     draco_metadata_dec
-    #     draco_point_cloud
-    #     draco_points_dec
-    #     draco_static
-    #     expected-lite
-    #     GSL
-    #     httplib
-    #     ktx
-    #     meshoptimizer
-    #     modp_b64
-    #     spdlog
-    #     sqlite3
-    #     s2geometry
-    #     tinyxml2
-    #     tidy-static
-    #     uriparser
-    #     webpdecode
-    #     webpdecoder
-    #     webpdspdecode
-    #     webputils
-    #     webputilsdecode
-    #     zlibstatic
-    # )
-    #set(MESHOPT_BUILD_SHARED_LIBS OFF BOOL FORCE)
     install(TARGETS tidy-static)
-    # install(
-    #   TARGETS ${ALL_TARGETS}
-    #   PUBLIC_HEADER
-    #     EXCLUDE_FROM_ALL
-    #   FRAMEWORK
-    #     DESTINATION ${CMAKE_INSTALL_LIBDIR}
-    # )
     set_target_properties(tidy-static PROPERTIES EXCLUDE_FROM_ALL 0 EXCLUDE_FROM_DEFAULT_BUILD 0)
-    #set_target_properties(${ALL_TARGETS} PROPERTIES XCODE_ATTRIBUTE_ENABLE_BITCODE "YES")
-
-    # ktx tags itself as a FRAMEWORK on iOS, which causes linker errors. Undo that.
-    #set_target_properties(ktx PROPERTIES FRAMEWORK FALSE)
 endif()
-
-

native~/Editor/CMakeLists.txt

@@ -41,7 +41,7 @@ target_link_libraries(
 set_target_properties(
     CesiumForUnityNative-Editor
     PROPERTIES
-        CXX_STANDARD 17
+        CXX_STANDARD 20
         CXX_STANDARD_REQUIRED YES
         CXX_EXTENSIONS NO
 )

native~/Runtime/CMakeLists.txt

@@ -44,12 +44,13 @@ target_link_libraries(
     PRIVATE
       tidy-static
       enum-flags
+      swl-variant
 )
 
 set_target_properties(
   CesiumForUnityNative-Runtime
     PROPERTIES
-        CXX_STANDARD 17
+        CXX_STANDARD 20
         CXX_STANDARD_REQUIRED YES
         CXX_EXTENSIONS NO
 )
@@ -66,6 +67,7 @@ target_compile_definitions(
   CesiumForUnityNative-Runtime
   PUBLIC
     TIDY_STATIC
+    SWL_VARIANT_NO_CONSTEXPR_EMPLACE
 )
 
 # If we're building for the Unity Editor, set a #define accordingly.

native~/Runtime/src/CesiumFeatureImpl.h

@@ -4,9 +4,9 @@
 
 #include <DotNet/CesiumForUnity/CesiumMetadataValue.h>
 #include <DotNet/CesiumForUnity/MetadataType.h>
+#include <swl/variant.hpp>
 
 #include <unordered_map>
-#include <variant>
 
 namespace DotNet::CesiumForUnity {
 class CesiumFeature;
@@ -18,7 +18,7 @@ class String;
 
 namespace CesiumForUnityNative {
 
-using ValueType = std::variant<
+using ValueType = swl::variant<
     int8_t,
     uint8_t,
     int16_t,