ogre-next: add darwin support

pkgs/by-name/og/ogre-next/package.nix

@@ -3,6 +3,7 @@
   stdenv,
   fetchFromGitHub,
   fetchpatch2,
+  testers,
 
   cmake,
   ninja,
@@ -21,6 +22,7 @@
   openvr,
   rapidjson,
   zziplib,
+  apple-sdk_15,
 }:
 stdenv.mkDerivation (finalAttrs: {
   pname = "ogre-next";
@@ -41,6 +43,35 @@ stdenv.mkDerivation (finalAttrs: {
     })
   ];
 
+  postPatch = ''
+    # OgreMain/CMakeLists.txt has a macOS post-build block that uses `ditto`
+    # (a macOS system tool unavailable in the Nix sandbox) to copy headers
+    # into an Ogre.framework bundle. This block runs unconditionally on
+    # non-iOS macOS — it is not gated by OGRE_BUILD_LIBS_AS_FRAMEWORKS.
+    # Wrap it in a framework guard so it is skipped when frameworks are
+    # disabled, avoiding the missing `ditto` and the unnecessary framework
+    # directory structure.
+    substituteInPlace OgreMain/CMakeLists.txt \
+      --replace-fail \
+        'set(OGRE_OSX_BUILD_CONFIGURATION "$(PLATFORM_NAME)/$(CONFIGURATION)")' \
+        'if (OGRE_BUILD_LIBS_AS_FRAMEWORKS)
+    set(OGRE_OSX_BUILD_CONFIGURATION "$(PLATFORM_NAME)/$(CONFIGURATION)")' \
+      --replace-fail \
+        'ogre_config_framework(''${OGRE_NEXT}Main)' \
+        'endif ()
+    ogre_config_framework(''${OGRE_NEXT}Main)'
+
+    # Remove Xcode-centric CMAKE_OSX_SYSROOT and CMAKE_OSX_ARCHITECTURES overrides.
+    # Nix stdenv already sets these correctly via apple-sdk.
+    substituteInPlace CMakeLists.txt \
+      --replace-fail 'set(XCODE_ATTRIBUTE_SDKROOT macosx)' "" \
+      --replace-fail 'set(CMAKE_OSX_SYSROOT macosx)' "" \
+      --replace-fail \
+        'execute_process(COMMAND xcodebuild -version -sdk "''${XCODE_ATTRIBUTE_SDKROOT}" Path | head -n 1 OUTPUT_VARIABLE CMAKE_OSX_SYSROOT)' "" \
+      --replace-fail \
+        'string(REGEX REPLACE "(\r?\n)+$" "" CMAKE_OSX_SYSROOT "''${CMAKE_OSX_SYSROOT}")' ""
+  '';
+
   nativeBuildInputs = [
     cmake
     pkg-config
@@ -53,7 +84,6 @@ stdenv.mkDerivation (finalAttrs: {
     zziplib
     zlib
     tinyxml
-    openvr
     rapidjson
   ]
   ++ lib.optionals stdenv.hostPlatform.isLinux [
@@ -63,7 +93,11 @@ stdenv.mkDerivation (finalAttrs: {
     libxrandr
     libxt
     libxcb
-  ];
+    # openvr is broken on darwin
+    openvr
+  ]
+  # apple-sdk_15 provides Metal, Cocoa, and OpenGL frameworks
+  ++ lib.optional stdenv.hostPlatform.isDarwin apple-sdk_15;
 
   # TODO: Figure out Vulkan plugin deps
 
@@ -73,18 +107,39 @@ stdenv.mkDerivation (finalAttrs: {
     # Use STB instead of freeimage since the latter is marked as insecure
     (lib.cmakeBool "OGRE_CONFIG_ENABLE_FREEIMAGE" false)
     (lib.cmakeBool "OGRE_CONFIG_ENABLE_STBI" true)
+
+    # Framework bundles are incompatible with the Nix store
+    (lib.cmakeBool "OGRE_BUILD_LIBS_AS_FRAMEWORKS" false)
+  ]
+  ++ lib.optionals stdenv.hostPlatform.isDarwin [
+    # GL3Plus requires Khronos headers not available on darwin; Metal is the
+    # primary render system on macOS
+    (lib.cmakeBool "OGRE_BUILD_RENDERSYSTEM_GL3PLUS" false)
+  ]
+  # Both NEON and SSE2 SIMD cause build failures on aarch64
+  ++ lib.optionals stdenv.hostPlatform.isAarch64 [
+    (lib.cmakeBool "OGRE_SIMD_NEON" false)
+    (lib.cmakeBool "OGRE_SIMD_SSE2" false)
   ];
 
+  passthru.tests.pkg-config = testers.hasPkgConfigModules {
+    package = finalAttrs.finalPackage;
+    versionCheck = true;
+  };
+
   meta = {
     description = "3D Object-Oriented Graphics Rendering Engine";
     homepage = "https://www.ogre3d.org/";
     maintainers = with lib.maintainers; [
       marcin-serwin
     ];
-    platforms = lib.platforms.linux;
+    pkgConfigModules = [
+      "OGRE"
+      "OGRE-Hlms"
+      "OGRE-MeshLodGenerator"
+      "OGRE-Overlay"
+    ];
+    platforms = lib.platforms.linux ++ lib.platforms.darwin;
     license = lib.licenses.mit;
-
-    # build problems around NEON intrinsics
-    broken = stdenv.hostPlatform.isAarch64;
   };
 })