add SDL_PATH env var

kivy/__init__.py

@@ -33,7 +33,7 @@ __version__ = '1.9.0-dev'
 import sys
 import shutil
 from getopt import getopt, GetoptError
-from os import environ, mkdir
+from os import environ, mkdir, pathsep
 from os.path import dirname, join, basename, exists, expanduser
 from kivy.logger import Logger, LOG_LEVELS
 from kivy.utils import platform
@@ -41,6 +41,11 @@ from kivy.utils import platform
 # internals for post-configuration
 __kivy_post_configuration = []
 
+# Use custom SDL2 libraries and headers if SDL_PATH is set, not the ones
+# installed system-wide.
+if 'SDL_PATH' in environ:
+    environ['PATH'] = pathsep.join((environ['SDL_PATH'], environ['PATH']))
+
 
 if platform == 'macosx' and sys.maxsize < 9223372036854775807:
     r = '''Unsupported Python version detected!:

setup.py

@@ -394,14 +394,16 @@ def determine_sdl2():
     if not c_options['use_sdl2']:
         return flags
 
-    sdl2_portable_path = join(dirname(__file__), 'kivy', 'lib', 'sdl2')
+    sdl2_path = environ['SDL_PATH'] if 'SDL_PATH' in environ else None
+
     flags['libraries'] = ['SDL2', 'SDL2_ttf', 'SDL2_image', 'SDL2_mixer']
-    flags['include_dirs'] = ['/usr/local/include/SDL2', '/usr/include/SDL2',
-        sdl2_portable_path]
+    flags['include_dirs'] = ([sdl2_path] if sdl2_path else
+                             ['/usr/local/include/SDL2', '/usr/include/SDL2'])
 
     flags['extra_link_args'] = []
     flags['extra_compile_args'] = []
-    flags['extra_link_args'] += ['-L/usr/local/lib/', '-L' + sdl2_portable_path]
+    flags['extra_link_args'] += (['-L' + sdl2_path] if sdl2_path else
+                             ['-L/usr/local/lib/'])
 
     # ensure headers for all the SDL2 and sub libraries are available
     libs_to_check = ['SDL', 'SDL_mixer', 'SDL_ttf', 'SDL_image']