blits. (Blits have their own way to pass the requisite rectangles
in.)
* ``set_tess_state`` configures the default tessellation parameters:
+
* ``default_outer_level`` is the default value for the outer tessellation
levels. This corresponds to GL's ``PATCH_DEFAULT_OUTER_LEVEL``.
* ``default_inner_level`` is the default value for the inner tessellation
levels. This corresponds to GL's ``PATCH_DEFAULT_INNER_LEVEL``.
+
* ``set_debug_callback`` sets the callback to be used for reporting
various debug messages, eventually reported via KHR_debug and
similar mechanisms.