Update to handle fat builds

Author: Martin King

3rdparty/png/CMakeLists.txt

@@ -22,51 +22,84 @@ set(${target_name}_src
   pngwutil.c
 )
 
-set(_PNG_ISA_SIMD ${AX_ISA_SIMD})
+add_library(${target_name} STATIC
+  ${${target_name}_src}
+)
+
+# -----------------------------------------------------------------------------
+# macOS Universal Binary Logic (Fat Build)
+# -----------------------------------------------------------------------------
+if(APPLE AND CMAKE_SYSTEM_NAME STREQUAL "Darwin")
+  # We rely on CMAKE_OSX_ARCHITECTURES being set by the user/system
+  # (e.g., -DCMAKE_OSX_ARCHITECTURES="arm64;x86_64") to control the output.
 
-if(_PNG_ISA_SIMD STREQUAL "neon")
-  set(libpng_arm_sources
+  # --- NEON OBJECT LIBRARY (for arm64 slice) ---
+  add_library(png_arm_neon OBJECT
     arm/arm_init.c
     arm/filter_neon_intrinsics.c
-    arm/palette_neon_intrinsics.c)
-
-  # notes:
-  # - android armv7: needs PNG_ARM_NEON_CHECK_SUPPORTED for very older devices, but axmol no longer support them
-  # PNG_ARM_NEON_IMPLEMENTATION:
-  # 1: use instrinsics
-  # 2: use handcode
-  set(libpng_optimize_flag "PNG_ARM_NEON_OPT=1")
-elseif(_PNG_ISA_SIMD MATCHES "sse")
-  set(libpng_intel_sources
+    arm/palette_neon_intrinsics.c
+  )
+  target_compile_definitions(png_arm_neon PRIVATE "PNG_ARM_NEON_OPT=1")
+
+  # Restrict compilation/use of these objects to the arm64 slice only
+  set_target_properties(png_arm_neon PROPERTIES
+    OSX_ARCHITECTURES "arm64"
+    COMPILE_FLAGS "-march=armv8-a+simd"
+  )
+
+  # --- SSE OBJECT LIBRARY (for x86_64 slice) ---
+  add_library(png_intel_sse OBJECT
     intel/intel_init.c
-    intel/filter_sse2_intrinsics.c)
-  set(libpng_optimize_flag "PNG_INTEL_SSE_OPT=1")
+    intel/filter_sse2_intrinsics.c
+  )
+  target_compile_definitions(png_intel_sse PRIVATE "PNG_INTEL_SSE_OPT=1")
+
+  # Restrict compilation/use of these objects to the x86_64 slice only
+  set_target_properties(png_intel_sse PROPERTIES
+    OSX_ARCHITECTURES "x86_64"
+    COMPILE_FLAGS "-msse2"
+  )
+
+  # Link object libraries into main library
+  target_sources(${target_name} PRIVATE
+    $<TARGET_OBJECTS:png_arm_neon>
+    $<TARGET_OBJECTS:png_intel_sse>
+  )
+
+# -----------------------------------------------------------------------------
+# Non-Darwin Conditional SIMD Logic (Android, iOS, Windows, Linux)
+# -----------------------------------------------------------------------------
+else()
+  set(_PNG_ISA_SIMD ${AX_ISA_SIMD})
+  if(_PNG_ISA_SIMD STREQUAL "neon")
+    target_sources(${target_name} PRIVATE
+      arm/arm_init.c
+      arm/filter_neon_intrinsics.c
+      arm/palette_neon_intrinsics.c)
+    target_compile_definitions(${target_name} PUBLIC "PNG_ARM_NEON_OPT=1")
+  elseif(_PNG_ISA_SIMD MATCHES "sse")
+    target_sources(${target_name} PRIVATE
+      intel/intel_init.c
+      intel/filter_sse2_intrinsics.c)
+    target_compile_definitions(${target_name} PUBLIC "PNG_INTEL_SSE_OPT=1")
+  endif()
 endif()
 
-add_library(${target_name} STATIC
-  ${${target_name}_src}
-  ${libpng_arm_sources}
-  ${libpng_intel_sources}
-)
 
-# cmake builtin FindPNG.cmake detect cached variable PNG_PNG_INCLUDE_DIR
 set(PNG_PNG_INCLUDE_DIR "${CMAKE_CURRENT_LIST_DIR}" CACHE INTERNAL "png include dir" FORCE)
-
 set(PNG_INCLUDE_DIR "${PNG_PNG_INCLUDE_DIR}" CACHE INTERNAL "" FORCE)
 target_include_directories(${target_name} PUBLIC "${PNG_INCLUDE_DIR}")
 
-if(_PNG_ISA_SIMD)
-  target_compile_definitions(${target_name} PUBLIC ${libpng_optimize_flag})
-endif()
-
 target_include_directories(${target_name} PRIVATE "${ZLIB_INCLUDE_DIR}")
 
+# Android Specific Linking for CPU Features
 if(ANDROID)
   target_include_directories(${target_name} PRIVATE ${cpufeatures_include_dir})
   target_link_libraries(${target_name} INTERFACE cpufeatures)
 endif()
 
-# Export png as PNG::PNG to avoid cmake builtin FindPNG.cmake add target again
+# Export png as PNG::PNG to avoid conflicts and enable modern linking
 add_library(PNG::PNG ALIAS ${target_name})
 
-set(PNG_LIBRARY "png" CACHE INTERNAL "png include dir" FORCE)
+# Set compatibility variable
+set(PNG_LIBRARY "png" CACHE INTERNAL "png library" FORCE)