Switch macOS static build to CMake (#1938)

This moves the tortuous flags out of our CI scripts,
and allows us to benefit from the libpng download caching.

.github/scripts/build_libpng.sh

@@ -1,23 +0,0 @@
-#!/bin/bash
-set -euo pipefail
-
-pngver=1.6.56
-
-## Grab sources and check them
-
-curl -LOJ "http://prdownloads.sourceforge.net/libpng/libpng-$pngver.tar.xz?download"
-echo f7d8bf1601b7804f583a254ab343a6549ca6cf27d255c302c47af2d9d36a6f18 \*libpng-$pngver.tar.xz | \
-	shasum -a 256 -c -
-
-## Extract sources and patch them
-
-tar -xvf libpng-$pngver.tar.xz
-
-## Start building!
-
-mkdir -p build
-cd build
-../libpng-$pngver/configure --disable-shared --enable-static \
-	CFLAGS="-O3 -flto -DNDEBUG -mmacosx-version-min=10.9 -arch x86_64 -arch arm64 -fno-exceptions"
-make -kj
-make install prefix="$PWD/../libpng-staging"

.github/workflows/create-release-artifacts.yml

@@ -54,13 +54,10 @@ jobs:
       - name: Install deps
         run: |
           ./.github/scripts/install_deps.sh macos
-      - name: Build libpng
-        run: |
-          ./.github/scripts/build_libpng.sh
-      # We force linking libpng statically; the other libs are provided by macOS itself
       - name: Build binaries
         run: |
-          make -kj CXXFLAGS="-O3 -flto -DNDEBUG -mmacosx-version-min=10.9 -arch x86_64 -arch arm64" PNGCFLAGS="-I libpng-staging/include" PNGLDLIBS="libpng-staging/lib/libpng.a -lz" Q=
+          cmake -S . -B build --preset macos-static -DFETCHCONTENT_BASE_DIR="${{ env.DEPS_ROOT_DIR }}"
+          cmake --build build
           strip rgb{asm,link,fix,gfx}
       - name: Package binaries
         run: |

.github/workflows/testing.yml

@@ -109,12 +109,16 @@ jobs:
       - name: Install deps
         run: |
           ./.github/scripts/install_deps.sh macos
-      - name: Build libpng
+      - name: Cache library deps
-        run: |
+        uses: actions/cache@v5
-          ./.github/scripts/build_libpng.sh
+        with:
+          path: ${{ env.DEPS_ROOT_DIR }}/*-tmp/
+          key: dep-srcs-${{ hashFiles('cmake/deps.cmake') }}
+          enableCrossOsArchive: true
       - name: Build & install
         run: |
-          make -kj CXXFLAGS="-O3 -flto -DNDEBUG -mmacosx-version-min=10.9 -arch x86_64 -arch arm64" PNGCFLAGS="-I libpng-staging/include" PNGLDLIBS="libpng-staging/lib/libpng.a -lz" Q=
+          cmake -S . -B build --preset macos-static -DFETCHCONTENT_BASE_DIR="${{ env.DEPS_ROOT_DIR }}"
+          cmake --build build
       - name: Package binaries
         run: |
           mkdir bins
@@ -168,7 +172,7 @@ jobs:
         with:
           path: ${{ env.DEPS_ROOT_DIR }}/*-tmp/
           key: dep-srcs-${{ hashFiles('cmake/deps.cmake') }}
-          enableCrossOsArchive: true # Currently only used on Windows, but the contents are OS-agnostic.
+          enableCrossOsArchive: true
       - name: Build Windows binaries
         run: | # ASan seems to be broken on Windows, so we disable it.
           cmake -S . -B build --preset develop-msvc${{ matrix.bits }} -DSANITIZERS=OFF \

CMakePresets.json

@@ -31,6 +31,14 @@
 			"name": "msvc64",
 			"description": "Flags for building 64-bit executables with MSVC",
 			"architecture": "x64"
+		},
+
+		{
+			"name": "macos-static",
+			"description": "Flags for building an executable compatible with old macOS",
+			"cacheVariables": {
+				"CMAKE_PROJECT_TOP_LEVEL_INCLUDES": "cmake/macos-static.cmake"
+			}
 		}
 	]
 }

cmake/macos-static.cmake

@@ -0,0 +1,28 @@
+# This file is meant to be included at the project level,
+# in order to generate executables compatible with old macOS versions.
+# See our `macos-static` CMake preset for how it's meant to be used.
+
+# The `-mmacosx-version-min=10.9` flag ensures that the binary only uses APIs available on Mac OS X 10.9 Mavericks.
+# The `-arch` flags build a "fat binary" that works on both Apple architectures:
+# older Intel x64 Macs and newer ARM "Apple Silicon" ones.
+set("-mmacosx-version-min=10.9 -arch x86_64 -arch arm64")
+set(CMAKE_C_FLAGS "${secret_sauce}" CACHE STRING "Flags used by the C compiler during all build types.")
+set(CMAKE_CXX_FLAGS "${secret_sauce}" CACHE STRING "Flags used by the CXX compiler during all build types.")
+
+# Mac OS X has always provided zlib, so we can safely link dynamically against it.
+# However, libpng is *not* provided by default, so we link it statically, which requires downloading and building it from source.
+set(PNG_SHARED OFF)
+set(PNG_STATIC ON)
+# If libpng is already available (e.g. via Homebrew), we ignore that and still build our own.
+set(FETCHCONTENT_TRY_FIND_PACKAGE_MODE NEVER)
+# But we still want to attempt linking against the system's zlib.
+function(rgbds_provide_dependency method dep_name)
+  if(dep_name STREQUAL "ZLIB")
+    find_package(ZLIB)
+    if(ZLIB_FOUND)
+      FetchContent_SetPopulated(ZLIB)
+    endif()
+  endif()
+endfunction(rgbds_provide_dependency)
+cmake_language(SET_DEPENDENCY_PROVIDER rgbds_provide_dependency
+               SUPPORTED_METHODS FETCHCONTENT_MAKEAVAILABLE_SERIAL)