Accept the same values of MUJOCO_GL as the mujoco package.

The `mujoco` package also makes use of the `MUJOCO_GL` environment variable to switch between rendering backends, which are implemented separately from the ones currently used in `dm_control`. However, `mujoco` accepts a wider range of `MUJOCO_GL` values, in particular it allows `off` to be specified to disable rendering entirely.

Before this change, specifying `MUJOCO_GL=off` will result in `dm_control` complaining that it is an invalid value. This change eliminates the conflicting `MUJOCO_GL` values expected by the two libraries.

Fixes #324.

PiperOrigin-RevId: 461577872
Change-Id: Ie962040395b766affc8342ab9d9fd09a0afe15cb

Author: saran-t

dm_control/_render/__init__.py

@@ -47,43 +47,59 @@ def _import_osmesa():
   return OSMesaContext
 # pylint: enable=g-import-not-at-top
 
-_ALL_RENDERERS = collections.OrderedDict([
+
+def _no_renderer():
+  def no_renderer(*args, **kwargs):
+    del args, kwargs
+    raise RuntimeError('No OpenGL rendering backend is available.')
+  return no_renderer
+
+
+_ALL_RENDERERS = (
     (constants.GLFW, _import_glfw),
     (constants.EGL, _import_egl),
     (constants.OSMESA, _import_osmesa),
-])
+)
+
+_NO_RENDERER = (
+    (constants.NO_RENDERER, _no_renderer),
+)
 
 
 if BACKEND is not None:
   # If a backend was specified, try importing it and error if unsuccessful.
-  try:
-    import_func = _ALL_RENDERERS[BACKEND]
-  except KeyError:
+  import_func = None
+  for names, importer in _ALL_RENDERERS + _NO_RENDERER:
+    if BACKEND in names:
+      import_func = importer
+      BACKEND = names[0]  # canonicalize the renderer name
+      break
+  if import_func is None:
+    all_names = set()
+    for names, _ in _ALL_RENDERERS + _NO_RENDERER:
+      all_names.update(names)
     raise RuntimeError(
         'Environment variable {} must be one of {!r}: got {!r}.'
-        .format(constants.MUJOCO_GL, _ALL_RENDERERS.keys(), BACKEND))
+        .format(constants.MUJOCO_GL, sorted(all_names), BACKEND))
   logging.info('MUJOCO_GL=%s, attempting to import specified OpenGL backend.',
                BACKEND)
-  Renderer = import_func()  # pylint: disable=invalid-name
+  Renderer = import_func()
 else:
   logging.info('MUJOCO_GL is not set, so an OpenGL backend will be chosen '
                'automatically.')
   # Otherwise try importing them in descending order of priority until
   # successful.
-  for name, import_func in _ALL_RENDERERS.items():
+  for names, import_func in _ALL_RENDERERS:
     try:
       Renderer = import_func()
-      BACKEND = name
-      logging.info('Successfully imported OpenGL backend: %s', name)
+      BACKEND = names[0]
+      logging.info('Successfully imported OpenGL backend: %s', names[0])
       break
     except ImportError:
-      logging.info('Failed to import OpenGL backend: %s', name)
+      logging.info('Failed to import OpenGL backend: %s', names[0])
   if BACKEND is None:
     logging.info('No OpenGL backend could be imported. Attempting to create a '
                  'rendering context will result in a RuntimeError.')
+    Renderer = _no_renderer()
 
-    def Renderer(*args, **kwargs):  # pylint: disable=function-redefined,invalid-name
-      del args, kwargs
-      raise RuntimeError('No OpenGL rendering backend is available.')
-
-USING_GPU = BACKEND in (constants.EGL, constants.GLFW)
+USING_GPU = BACKEND in constants.EGL + constants.GLFW

dm_control/_render/constants.py

@@ -22,6 +22,11 @@
 PYOPENGL_PLATFORM = 'PYOPENGL_PLATFORM'
 
 # Renderer platform specifiers.
-OSMESA = 'osmesa'
-GLFW = 'glfw'
-EGL = 'egl'
+# All values in each tuple are synonyms for the MUJOCO_GL environment variable.
+# The first entry in each tuple is considered "canonical", and is the one
+# assigned to the _render.BACKEND variable.
+OSMESA = ('osmesa',)
+GLFW = ('glfw', 'on', 'enable', 'enabled', 'true', '1', '')
+EGL = ('egl',)
+NO_RENDERER = ('off', 'disable', 'disabled', 'false', '0')
+

dm_control/_render/glfw_renderer_test.py

@@ -30,7 +30,7 @@
 
 
 @unittest.skipUnless(
-    _render.BACKEND == _render.constants.GLFW,
+    _render.BACKEND == _render.constants.GLFW[0],
     reason='GLFW beckend not selected.')
 class GLFWContextTest(absltest.TestCase):
 

dm_control/_render/pyopengl/egl_renderer.py

@@ -26,13 +26,13 @@
 PYOPENGL_PLATFORM = os.environ.get(constants.PYOPENGL_PLATFORM)
 
 if not PYOPENGL_PLATFORM:
-  os.environ[constants.PYOPENGL_PLATFORM] = constants.EGL
-elif PYOPENGL_PLATFORM != constants.EGL:
+  os.environ[constants.PYOPENGL_PLATFORM] = constants.EGL[0]
+elif PYOPENGL_PLATFORM != constants.EGL[0]:
   raise ImportError(
       'Cannot use EGL rendering platform. '
       'The PYOPENGL_PLATFORM environment variable is set to {!r} '
       '(should be either unset or {!r}).'
-      .format(PYOPENGL_PLATFORM, constants.EGL))
+      .format(PYOPENGL_PLATFORM, constants.EGL[0]))
 
 
 # pylint: disable=g-import-not-at-top
@@ -100,7 +100,7 @@ def __init__(self, max_width, max_height):
 
   def _platform_init(self, unused_max_width, unused_max_height):
     """Initialization this EGL context."""
-    num_configs = ctypes.c_long()
+    num_configs = ctypes.c_long(0)
     config_size = 1
     config = EGL.EGLConfig()
     EGL.eglReleaseThread()

dm_control/_render/pyopengl/osmesa_renderer.py

@@ -23,13 +23,13 @@
 PYOPENGL_PLATFORM = os.environ.get(constants.PYOPENGL_PLATFORM)
 
 if not PYOPENGL_PLATFORM:
-  os.environ[constants.PYOPENGL_PLATFORM] = constants.OSMESA
-elif PYOPENGL_PLATFORM != constants.OSMESA:
+  os.environ[constants.PYOPENGL_PLATFORM] = constants.OSMESA[0]
+elif PYOPENGL_PLATFORM != constants.OSMESA[0]:
   raise ImportError(
       'Cannot use OSMesa rendering platform. '
       'The PYOPENGL_PLATFORM environment variable is set to {!r} '
       '(should be either unset or {!r}).'
-      .format(PYOPENGL_PLATFORM, constants.OSMESA))
+      .format(PYOPENGL_PLATFORM, constants.OSMESA[0]))
 
 # pylint: disable=g-import-not-at-top
 from OpenGL import GL