Allow overriding the game engine external libraries with ones provided by the game. (#358)

Author: rh101

CMakeLists.txt

@@ -1,50 +1,108 @@
 cmake_minimum_required(VERSION 3.6)
 project(external)
 
-add_library(external empty.cpp)
+option(BUILD_EXT_BOX2D "Build with internal Box2D support" ON)
+option(BUILD_EXT_CHIPMUNK "Build with internal chipmunk support" ON)
+option(BUILD_EXT_FREETYPE2 "Build with internal freetype2 support" ON)
+option(BUILD_EXT_RECAST "Build with internal recast support" ON)
+option(BUILD_EXT_BULLET "Build with internal bullet support" ON)
+option(BUILD_EXT_JPEG "Build with internal jpeg support" ON)
+option(BUILD_EXT_OPENSSL "Build with internal openssl support" ON)
+option(BUILD_EXT_TIFF "Build with internal tiff support" ON)
+option(BUILD_EXT_UV "Build with internal uv support" ON)
+option(BUILD_EXT_WEBP "Build with internal webp support" ON)
+option(BUILD_EXT_WEBSOCKETS "Build with internal websockets support" ON)
+option(BUILD_EXT_TINYXML2 "Build with internal tinyxml2 support" ON)
+option(BUILD_EXT_XXHASH "Build with internal xxhash support" ON)
+option(BUILD_EXT_XXTEA "Build with internal xxtea support" ON)
+option(BUILD_EXT_CLIPPER "Build with internal clipper support" ON)
+option(BUILD_EXT_EDTAA3FUNC "Build with internal edtaa3func support" ON)
+option(BUILD_EXT_CONVERTUTF "Build with internal ConvertUTF support" ON)
+option(BUILD_EXT_POLY2TRI "Build with internal poly2tri support" ON)
+option(BUILD_EXT_MD5 "Build with internal md5 support" ON)
+option(BUILD_EXT_SQLITE "Build with internal SQLite support" ON)
+option(BUILD_EXT_ZLIB "Build with internal zlib support" ON)
+option(BUILD_EXT_CURL "Build with internal curl support" ON)
 
-add_subdirectory(Box2D)
-add_subdirectory(chipmunk)
-add_subdirectory(freetype2)
-add_subdirectory(recast)
-add_subdirectory(bullet)
-add_subdirectory(jpeg)
-add_subdirectory(openssl)
-add_subdirectory(tiff)
-add_subdirectory(uv)
-add_subdirectory(webp)
-add_subdirectory(websockets)
-add_subdirectory(tinyxml2)
-add_subdirectory(xxhash)
-add_subdirectory(xxtea)
-add_subdirectory(clipper)
-add_subdirectory(edtaa3func)
-add_subdirectory(ConvertUTF)
-add_subdirectory(poly2tri)
-add_subdirectory(md5)
+add_library(external empty.cpp)
 
-target_link_libraries(external
-    ext_box2d
-    ext_chipmunk
-    ext_freetype
-    ext_recast
-    ext_jpeg
-    ext_uv
-    ext_webp
-    ext_bullet
-    ext_ssl
-    ext_crypto
-    ext_tiff
-    ext_websockets
-    ext_tinyxml2
-    ext_xxhash
-    ext_xxtea
-    ext_clipper
-    ext_edtaa3func
-    ext_convertUTF
-    ext_poly2tri
-    ext_md5
-)
+if(BUILD_EXT_BOX2D)
+    add_subdirectory(Box2D)
+    target_link_libraries(external ext_box2d)
+endif(BUILD_EXT_BOX2D)
+if(BUILD_EXT_CHIPMUNK)
+    add_subdirectory(chipmunk)
+    target_link_libraries(external ext_chipmunk)
+endif(BUILD_EXT_CHIPMUNK)
+if(BUILD_EXT_FREETYPE2)
+    add_subdirectory(freetype2)
+    target_link_libraries(external ext_freetype)
+endif(BUILD_EXT_FREETYPE2)
+if(BUILD_EXT_RECAST)
+    add_subdirectory(recast)
+    target_link_libraries(external ext_recast)
+endif(BUILD_EXT_RECAST)
+if(BUILD_EXT_BULLET)
+    add_subdirectory(bullet)
+    target_link_libraries(external ext_bullet)
+endif(BUILD_EXT_BULLET)
+if(BUILD_EXT_JPEG)
+    add_subdirectory(jpeg)
+    target_link_libraries(external ext_jpeg)
+endif(BUILD_EXT_JPEG)
+if(BUILD_EXT_OPENSSL)
+    add_subdirectory(openssl)
+    target_link_libraries(external ext_ssl)
+    target_link_libraries(external ext_crypto)
+endif(BUILD_EXT_OPENSSL)
+if(BUILD_EXT_TIFF)
+    add_subdirectory(tiff)
+    target_link_libraries(external ext_tiff)
+endif(BUILD_EXT_TIFF)
+if(BUILD_EXT_UV)
+    add_subdirectory(uv)
+    target_link_libraries(external ext_uv)
+endif(BUILD_EXT_UV)
+if(BUILD_EXT_WEBP)
+    add_subdirectory(webp)
+    target_link_libraries(external ext_webp)
+endif(BUILD_EXT_WEBP)
+if(BUILD_EXT_WEBSOCKETS)
+    add_subdirectory(websockets)
+    target_link_libraries(external ext_websockets)
+endif(BUILD_EXT_WEBSOCKETS)
+if(BUILD_EXT_TINYXML2)
+    add_subdirectory(tinyxml2)
+    target_link_libraries(external ext_tinyxml2)
+endif(BUILD_EXT_TINYXML2)
+if(BUILD_EXT_XXHASH)
+    add_subdirectory(xxhash)
+    target_link_libraries(external ext_xxhash)
+endif(BUILD_EXT_XXHASH)
+if(BUILD_EXT_XXTEA)
+    add_subdirectory(xxtea)
+    target_link_libraries(external ext_xxtea)
+endif(BUILD_EXT_XXTEA)
+if(BUILD_EXT_CLIPPER)
+    add_subdirectory(clipper)
+    target_link_libraries(external ext_clipper)
+endif(BUILD_EXT_CLIPPER)
+if(BUILD_EXT_EDTAA3FUNC)
+    add_subdirectory(edtaa3func)
+    target_link_libraries(external ext_edtaa3func)
+endif(BUILD_EXT_EDTAA3FUNC)
+if(BUILD_EXT_CONVERTUTF)
+    add_subdirectory(ConvertUTF)
+    target_link_libraries(external ext_convertUTF)
+endif(BUILD_EXT_CONVERTUTF)
+if(BUILD_EXT_POLY2TRI)
+    add_subdirectory(poly2tri)
+    target_link_libraries(external ext_poly2tri)
+endif(BUILD_EXT_POLY2TRI)
+if(BUILD_EXT_MD5)
+    add_subdirectory(md5)
+    target_link_libraries(external ext_md5)
+endif(BUILD_EXT_MD5)
 
 # use lua/js specific libs by property to prevent conflict
 if(BUILD_JS_LIBS)
@@ -63,10 +121,12 @@ if(BUILD_LUA_LIBS)
 endif()
 
 if(NOT LINUX)
-    add_subdirectory(curl)
+    if(BUILD_EXT_CURL)
+        add_subdirectory(curl)
+        target_link_libraries(external ext_curl)
+    endif(BUILD_EXT_CURL)
     add_subdirectory(png)
     target_link_libraries(external 
-        ext_curl
         ext_png
     )
 endif(NOT LINUX)
@@ -91,14 +151,16 @@ endif()
 
 if(WINDOWS)
     # sqlite3 prebuilt only existed at windows
-    add_subdirectory(sqlite3)
+    if(BUILD_EXT_SQLITE)
+        add_subdirectory(sqlite3)
+        target_link_libraries(external ext_sqlite3)
+    endif(BUILD_EXT_SQLITE)
     add_subdirectory(win32-specific/gles)
     add_subdirectory(win32-specific/icon)
     add_subdirectory(win32-specific/MP3Decoder)
     add_subdirectory(win32-specific/OggDecoder)
     add_subdirectory(win32-specific/OpenalSoft)
     target_link_libraries(external 
-        ext_sqlite3
         ext_gles
         ext_icon
         ext_MP3Decoder
@@ -115,15 +177,19 @@ if(WINDOWS OR MACOSX OR LINUX)
 endif()
 
 if(MACOSX OR ANDROID OR WINDOWS)
-    add_subdirectory(zlib)
-    target_link_libraries(external 
-        ext_zlib
-    )
+    if(BUILD_EXT_ZLIB)
+        add_subdirectory(zlib)
+        target_link_libraries(external 
+            ext_zlib
+        )
+    endif(BUILD_EXT_ZLIB)
 endif()
 
 # unzip depend on zlib
-add_subdirectory(unzip)
-target_link_libraries(external ext_unzip)
+if(BUILD_EXT_UNZIP)
+    add_subdirectory(unzip)
+    target_link_libraries(external ext_unzip)
+endif(BUILD_EXT_UNZIP)
 
 # put "external" into External folder, too
 set_target_properties(external