cmake: make possible to build both game and engine against the engine Freetype submodule

Author: illwieckz

CMakeLists.txt

@@ -778,17 +778,21 @@ endif()
 option(PREFER_EXTERNAL_LIBS "Tries to use system libs where possible." ON)
 
 macro(prefer_package LIB_NAME LIB_CMAKE)
-    if (PREFER_EXTERNAL_LIBS AND NOT NACL)
-        find_package(${LIB_NAME})
+	if (NOT ${LIB_NAME}_FOUND)
+		if (PREFER_EXTERNAL_LIBS AND NOT NACL)
+			find_package(${LIB_NAME})
 
-        if (NOT ${LIB_NAME}_FOUND)
-            message(WARNING "PREFER_EXTERNAL_LIBS is enabled but external ${LIB_NAME} is not found, falling back to vendored ${LIB_NAME}.")
-        endif()
-    endif()
+			if (NOT ${LIB_NAME}_FOUND)
+				message(WARNING "PREFER_EXTERNAL_LIBS is enabled but external ${LIB_NAME} is not found, falling back to vendored ${LIB_NAME}.")
+			endif()
+		endif()
 
-    if (NOT ${LIB_NAME}_FOUND)
-        include(${LIB_CMAKE})
-    endif()
+		if (NOT ${LIB_NAME}_FOUND)
+			include(${LIB_CMAKE})
+
+			set(${LIB_NAME}_FOUND ON)
+		endif()
+	endif()
 endmacro()
 
 if (BUILD_CLIENT)
@@ -817,7 +821,6 @@ if (BUILD_CLIENT)
     set(LIBS_CLIENT ${LIBS_CLIENT} ${PNG_LIBRARIES})
 
     prefer_package(Freetype ${DAEMON_DIR}/freetype.cmake)
-
     include_directories(${FREETYPE_INCLUDE_DIRS})
     set(LIBS_CLIENT ${LIBS_CLIENT} ${FREETYPE_LIBRARIES})
 

freetype.cmake

@@ -2,24 +2,33 @@ set(FREETYPE_DIR ${DAEMON_DIR}/libs/freetype)
 set(FREETYPE_INCLUDE_DIRS ${FREETYPE_DIR}/include)
 set(FREETYPE_LIBRARIES freetype)
 
-option(FT_DISABLE_BROTLI "Disable Brotli" ON)
-option(FT_DISABLE_BZIP2 "Disable bzip2" ON)
-option(FT_DISABLE_HARFBUZZ "Disable HarfBuzz" ON)
-option(FT_DISABLE_PNG "Disable PNG" ON)
-
 if (PREFER_EXTERNAL_LIBS AND NOT NACL)
 	set(FREETYPE_INTERNAL_ZLIB OFF)
 else()
 	set(FREETYPE_INTERNAL_ZLIB ON)
 endif()
 
-set(FT_DISABLE_ZLIB ${FREETYPE_INTERNAL_ZLIB} CACHE BOOL "Disable external zlib" FORCE)
+if (NOT ${FREETYPE_INTERNAL_ZLIB})
+	find_package(ZLIB REQUIRED)
+	set(FREETYPE_LIBRARIES ${FREETYPE_LIBRARIES} ${ZLIB_LIBRARIES})
+endif()
+
+# Do not re-add the target if already set to be built.
+# For example both the engine and a native game may request Freetype
+# to be built, but we need to only build once for both.
+if (NOT TARGET freetype)
+	option(FT_DISABLE_BROTLI "Disable Brotli" ON)
+	option(FT_DISABLE_BZIP2 "Disable bzip2" ON)
+	option(FT_DISABLE_HARFBUZZ "Disable HarfBuzz" ON)
+	option(FT_DISABLE_PNG "Disable PNG" ON)
+	set(FT_DISABLE_ZLIB ${FREETYPE_INTERNAL_ZLIB} CACHE BOOL "Disable external zlib" FORCE)
 
-add_subdirectory(${FREETYPE_DIR})
+	add_subdirectory(${FREETYPE_DIR})
 
-mark_as_advanced(FT_DISABLE_BROTLI)
-mark_as_advanced(FT_DISABLE_BZIP2)
-mark_as_advanced(FT_DISABLE_HARFBUZZ)
-mark_as_advanced(FT_DISABLE_PNG)
-mark_as_advanced(FT_DISABLE_ZLIB)
-mark_as_advanced(FT_ENABLE_ERROR_STRINGS)
+	mark_as_advanced(FT_DISABLE_BROTLI)
+	mark_as_advanced(FT_DISABLE_BZIP2)
+	mark_as_advanced(FT_DISABLE_HARFBUZZ)
+	mark_as_advanced(FT_DISABLE_PNG)
+	mark_as_advanced(FT_DISABLE_ZLIB)
+	mark_as_advanced(FT_ENABLE_ERROR_STRINGS)
+endif()