Add protobuf forced-config-mode compatibility, which was needed on macos

cmake/oe_osx.cmake

@@ -2,7 +2,7 @@
 
 # Set defaults for Universal Binaries. We want 32-bit Intel/PPC on 10.4
 # and 32/64-bit Intel/PPC on >= 10.5. Anything <= 10.3 doesn't support.
-IF(APPLE AND NOT ANDROID)
+IF(APPLE)
 
     # These are just defaults/recommendations, but how we want to build
     # out of the box. But the user needs to be able to change these options.
@@ -34,5 +34,8 @@ IF(APPLE AND NOT ANDROID)
     OPTION(OSGEARTH_BUILD_APPLICATION_BUNDLES "Enable the building of applications and examples as OSX Bundles" OFF)
     OPTION(OSGEARTH_BUILD_FRAMEWORKS "Compile frameworks instead of dylibs" OFF)
     SET(OSGEARTH_BUILD_FRAMEWORKS_INSTALL_NAME_DIR "@executable_path/../Frameworks" CACHE STRING "Install name dir for compiled frameworks")
+
+    # MacOS required this in order to find the protobuf_generate_cpp function:
+    set(OSGEARTH_PROTOBUF_FORCE_CONFIG_MODE ON)
 
-ENDIF(APPLE AND NOT ANDROID)
+ENDIF()

src/osgEarth/CMakeLists.txt

@@ -15,7 +15,6 @@ find_package(SQLite3 REQUIRED)
 
 # optional
 find_package(geos QUIET)
-find_package(Protobuf QUIET)
 find_package(blend2d QUIET)
 find_package(blosc QUIET)
 find_package(spdlog QUIET)
@@ -25,6 +24,14 @@ if(OSGEARTH_BUILD_ZIP_PLUGIN)
     find_package(LibZip QUIET)
 endif()
 
+if(OSGEARTH_PROTOBUF_FORCE_CONFIG_MODE)
+    # https://stackoverflow.com/a/56896032/4218920
+    set(protobuf_MODULE_COMPATIBLE ON CACHE BOOL "")
+    find_package(Protobuf CONFIG QUIET)
+else()
+    find_package(Protobuf QUIET)
+endif()
+
 
 # Other options ...................................................
 
@@ -819,9 +826,9 @@ endif()
 
 
 # generate the google protocol buffers headers and sources
-if(Protobuf_FOUND AND Protobuf_PROTOC_EXECUTABLE)
-    PROTOBUF_GENERATE_CPP(PROTO_VECTOR_TILE_CPP PROTO_VECTOR_TILE_H vector_tile.proto) 
-    PROTOBUF_GENERATE_CPP(PROTO_GLYPHS_CPP PROTO_GLYPHS_H glyphs.proto)    
+if(Protobuf_FOUND AND Protobuf_PROTOC_EXECUTABLE)    
+    protobuf_generate_cpp(PROTO_VECTOR_TILE_CPP PROTO_VECTOR_TILE_H vector_tile.proto) 
+    protobuf_generate_cpp(PROTO_GLYPHS_CPP PROTO_GLYPHS_H glyphs.proto)    
     list(APPEND TARGET_H ${PROTO_VECTOR_TILE_H} ${PROTO_GLYPHS_H})
     list(APPEND TARGET_SRC ${PROTO_VECTOR_TILE_CPP} ${PROTO_GLYPHS_CPP})