build: Universal macOS Library (#625)

* cross-compiling on M1 mac

* disable NEON on Intel mac

* add CMAKE_SYSTEM_ARCHITECTURES

WORKSPACE

@@ -245,6 +245,12 @@ http_archive(
 http_archive(
     name = "opencv",
     build_file = "@//third_party:opencv.BUILD",
+    patch_args = [
+        "-p1",
+    ],
+    patches = [
+        "@//third_party:opencv_disable_neon.diff",
+    ],
     sha256 = "5e37b791b2fe42ed39b52d9955920b951ee42d5da95f79fbc9765a08ef733399",
     strip_prefix = "opencv-3.4.16",
     urls = ["https://github.com/opencv/opencv/archive/3.4.16.tar.gz"],
@@ -334,6 +340,22 @@ load("@local_config_android//:android_configure.bzl", "android_workspace")
 android_workspace()
 
 # iOS basic build deps.
+http_archive(
+    name = "build_bazel_apple_support",
+    patch_args = [
+        "-p1",
+    ],
+    patches = [
+        "@//third_party:build_bazel_apple_support_transitions.diff",
+    ],
+    sha256 = "df317473b5894dd8eb432240d209271ebc83c76bb30c55481374b36ddf1e4fd1",
+    url = "https://github.com/bazelbuild/apple_support/releases/download/1.0.0/apple_support.1.0.0.tar.gz",
+)
+
+load(
+    "@build_bazel_apple_support//lib:repositories.bzl",
+    "apple_support_dependencies",
+)
 
 http_archive(
     name = "build_bazel_rules_apple",
@@ -363,21 +385,6 @@ load(
 
 swift_rules_dependencies()
 
-http_archive(
-    name = "build_bazel_apple_support",
-    sha256 = "741366f79d900c11e11d8efd6cc6c66a31bfb2451178b58e0b5edc6f1db17b35",
-    urls = [
-        "https://github.com/bazelbuild/apple_support/releases/download/0.10.0/apple_support.0.10.0.tar.gz",
-    ],
-)
-
-load(
-    "@build_bazel_apple_support//lib:repositories.bzl",
-    "apple_support_dependencies",
-)
-
-apple_support_dependencies()
-
 # More iOS deps.
 
 http_archive(

build.py

@@ -98,6 +98,9 @@ def _unzip(self, source, dest):
   def _is_windows(self):
     return self.system == 'Windows'
 
+  def _is_macos(self):
+    return self.system == 'Darwin'
+
 
 class BuildCommand(Command):
   def __init__(self, command_args):
@@ -256,6 +259,12 @@ def _build_desktop_options(self):
     else:
       commands += ['--define', 'MEDIAPIPE_DISABLE_GPU=1']
 
+    if self.command_args.macos_universal:
+      if self._is_macos():
+        commands += ['--//mediapipe_api:macos_universal']
+      else:
+        self.console.warn("Ignoring the `--macos_universal` option.")
+
     commands += self._build_opencv_switch()
 
     return commands
@@ -426,6 +435,7 @@ def __init__(self):
         choices=['face_detection', 'face_mesh', 'iris', 'hands', 'pose', 'holistic', 'selfie_segmentation', 'hair_segmentation', 'object_detection', 'box_tracking', 'instant_motion_tracking', 'objectron'])
     build_command_parser.add_argument('--linkopt', '-l', action='append', help='Linker options')
     build_command_parser.add_argument('--apple_bitcode', action=argparse.BooleanOptionalAction, default=True, help='Embed bitcode to iOS Framework')
+    build_command_parser.add_argument('--macos_universal', action=argparse.BooleanOptionalAction, default=False, help='Build a universal library')
     build_command_parser.add_argument('--bazel_startup_opts', action='append', help='Bazel startup options')
     build_command_parser.add_argument('--bazel_build_opts', action='append', help='Bazel startup options')
     build_command_parser.add_argument('--verbose', '-v', action='count', default=0)

mediapipe_api/BUILD

@@ -6,8 +6,21 @@
 
 load("//mediapipe_api:import_model.bzl", "pkg_asset")
 load("@bazel_skylib//lib:selects.bzl", "selects")
-load("@bazel_skylib//rules:common_settings.bzl", "string_list_flag")
+load("@bazel_skylib//rules:common_settings.bzl", "bool_flag", "string_list_flag")
 load("@rules_pkg//:pkg.bzl", "pkg_zip")
+load("@build_bazel_apple_support//rules:universal_binary.bzl", "universal_binary")
+
+bool_flag(
+    name = "macos_universal",
+    build_setting_default = False,
+)
+
+config_setting(
+    name = "build_universal_library",
+    flag_values = {
+        ":macos_universal": "True"
+    },
+)
 
 string_list_flag(
     name = "solutions",
@@ -213,13 +226,31 @@ cc_binary(
 )
 
 cc_binary(
-    name = "libmediapipe_c.dylib",
+    name = "libmediapipe_c_.dylib",
     linkshared = True,
     linkstatic = True,
     visibility = ["//visibility:public"],
     deps = [":mediapipe_c"],
 )
 
+universal_binary(
+    name = "libmediapipe_c_universal.dylib",
+    binary = ":libmediapipe_c_.dylib",
+)
+
+genrule(
+    name = "libmediapipe_c_dylib",
+    srcs = select({
+        ":build_universal_library": [":libmediapipe_c_universal.dylib"],
+        "//conditions:default": [":libmediapipe_c_.dylib"],
+    }),
+    outs = ["libmediapipe_c.dylib"],
+    cmd = select({
+        ":build_universal_library": "cp $< $(@D)/libmediapipe_c.dylib",
+        "//conditions:default": "cp $< $(@D)/libmediapipe_c.dylib",
+    }),
+)
+
 cc_binary(
     name = "mediapipe_c.dll",
     linkshared = True,
@@ -245,7 +276,7 @@ cc_binary(
 alias(
     name = "libmediapipe_c",
     actual = select({
-        "@com_google_mediapipe//mediapipe:macos": ":libmediapipe_c.dylib",
+        "@com_google_mediapipe//mediapipe:macos": ":libmediapipe_c_dylib",
         "@com_google_mediapipe//mediapipe:windows": ":mediapipe_c.dll",
         "@com_google_mediapipe//mediapipe:emscripten": ":libmediapipe_c.bc",
         "//conditions:default": ":libmediapipe_c.so",

third_party/build_bazel_apple_support_transitions.diff

@@ -0,0 +1,13 @@
+diff --git a/lib/transitions.bzl b/lib/transitions.bzl
+index f07e628..1e48a26 100644
+--- a/lib/transitions.bzl
++++ b/lib/transitions.bzl
+@@ -18,7 +18,7 @@ def _macos_universal_transition_impl(settings, _attr):
+     # Create a split transition from any macOS cpu to a list of all macOS cpus
+     if settings["//command_line_option:cpu"].startswith("darwin"):
+         return [
+-            {"//command_line_option:cpu": "darwin_x86_64"},
++            {"//command_line_option:cpu": "darwin"},
+             {"//command_line_option:cpu": "darwin_arm64"},
+         ]
+     else:

third_party/opencv.BUILD

@@ -72,6 +72,17 @@ selects.config_setting_group(
     match_all = ["@bazel_tools//src/conditions:windows", ":local_build"],
 )
 
+config_setting(
+    name = "enable_neon",
+    constraint_values = [
+        "@platforms//os:macos",
+        "@platforms//cpu:arm64",
+    ],
+    values = {
+        "cpu": "darwin_arm64",
+    },
+)
+
 alias(
     name = "opencv",
     actual = select({
@@ -126,6 +137,7 @@ OPENCV_3RDPARTY_LIBS = [
     "zlib",
 ]
 
+# ENABLE_NEON=ON
 OPENCV_3RDPARTY_LIBS_M1 = OPENCV_3RDPARTY_LIBS + ["tegra_hal"]
 
 define_string_dict(
@@ -191,7 +203,7 @@ define_string_dict(
 )
 
 define_string_dict(
-    name = "*nix_cache_entries",
+    name = "*nix_build_entries",
     value = {
         # https://github.com/opencv/opencv/issues/19846
         "WITH_LAPACK": "OFF",
@@ -200,6 +212,43 @@ define_string_dict(
     },
 )
 
+define_string_dict(
+    name = "darwin_arch_entries",
+    value = select({
+        "@cpuinfo//:macos_arm64": {
+            "CMAKE_SYSTEM_ARCHITECTURES": "arm64",
+            "CMAKE_OSX_ARCHITECTURES": "arm64",
+        },
+        "//conditions:default": {
+            "CMAKE_SYSTEM_ARCHITECTURES": "x86_64",
+            "CMAKE_OSX_ARCHITECTURES": "x86_64",
+        },
+    })
+)
+
+define_string_dict(
+    name = "neon_entries",
+    value = select({
+        ":enable_neon": {
+            "ENABLE_NEON": "ON",
+        },
+        "//conditions:default": {
+            "ENABLE_NEON": "OFF",
+        },
+    }),
+)
+
+merge_dict(
+    name = "*nix_cache_entries",
+    deps = [
+        ":*nix_build_entries",
+        ":neon_entries",
+    ] + select({
+        "@bazel_tools//src/conditions:darwin": [":darwin_arch_entries"],
+        "//conditions:default": [],
+    }),
+)
+
 merge_dict(
     name = "cache_entries",
     deps = [
@@ -244,7 +293,7 @@ cmake(
         ":cmake_dynamic": [],
         ":dbg_cmake_static_win": ["staticlib/%sd.lib" % lib for lib in OPENCV_3RDPARTY_LIBS],
         "@bazel_tools//src/conditions:windows": ["staticlib/%s.lib" % lib for lib in OPENCV_3RDPARTY_LIBS],
-        "@bazel_tools//src/conditions:darwin_arm64": ["share/OpenCV/3rdparty/lib/lib%s.a" % lib for lib in OPENCV_3RDPARTY_LIBS_M1],
+        ":enable_neon": ["share/OpenCV/3rdparty/lib/lib%s.a" % lib for lib in OPENCV_3RDPARTY_LIBS_M1],
         "//conditions:default": ["share/OpenCV/3rdparty/lib/lib%s.a" % lib for lib in OPENCV_3RDPARTY_LIBS],
     }) + select({
         ":cmake_static": [],

third_party/opencv_disable_neon.diff

@@ -0,0 +1,13 @@
+diff --git a/3rdparty/libpng/CMakeLists.txt b/3rdparty/libpng/CMakeLists.txt
+index efa59627eb..b1c18805ff 100644
+--- a/3rdparty/libpng/CMakeLists.txt
++++ b/3rdparty/libpng/CMakeLists.txt
+@@ -38,6 +38,8 @@ if(ARM OR AARCH64)
+   else()
+     add_definitions(-DPNG_ARM_NEON_OPT=0) # NEON assembler is not supported
+   endif()
++else()
++  add_definitions(-DPNG_ARM_NEON_OPT=0) # NEON assembler is not supported
+ endif()
+
+ if(";${CPU_BASELINE_FINAL};" MATCHES "SSE2"