mujoco.MjrContext.free instead of relying on the destructor.

Explicitly calling free() ensures that this operation happens within the right GL context.

PiperOrigin-RevId: 436226143
Change-Id: I556f621e88233e7a10ee5bec91a8cdfeab7c558c

dm_control/_render/base.py

@@ -67,6 +67,12 @@ def _free_at_exit():
   def keep_alive(self, obj):
     self._patients.append(obj)
 
+  def dont_keep_alive(self, obj):
+    try:
+      self._patients.remove(obj)
+    except ValueError:
+      pass
+
   def increment_refcount(self):
     self._refcount += 1
 
@@ -91,6 +97,8 @@ def _free_on_executor_thread(self):  # pylint: disable=missing-function-docstrin
       while self._patients:
         patient = self._patients.pop()
         assert sys.getrefcount(patient) == sys.getrefcount(dummy)
+        if hasattr(patient, 'free'):
+          patient.free()
         del patient
     finally:
       self._platform_free()

dm_control/mujoco/wrapper/core.py

@@ -620,6 +620,13 @@ def free(self):
     necessary. This MjrContext object MUST NOT be used after this function has
     been called.
     """
+    if self._gl_context and not self._gl_context.terminated:
+      ptr = self.ptr
+      if ptr:
+        self._gl_context.dont_keep_alive(ptr)
+        with self._gl_context.make_current() as ctx:
+          ctx.call(ptr.free)
+
     if self._gl_context:
       self._gl_context.decrement_refcount()
       self._gl_context.free()