text: # Copyright 2018-2021 The glTF-Blender-IO authors.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  import bpy
  
  from .gltf2_blender_node import BlenderNode
  from .gltf2_blender_animation import BlenderAnimation
  from .gltf2_blender_vnode import VNode, compute_vnodes
  from ..com.gltf2_blender_extras import set_extras
  from io_scene_gltf2.io.imp.gltf2_io_user_extensions import import_user_extensions
  
  
  class BlenderScene():
      """Blender Scene."""
      def __new__(cls, *args, **kwargs):
          raise RuntimeError("%s should not be instantiated" % cls)
  
      @staticmethod
      def create(gltf):
          """Scene creation."""
          scene = bpy.context.scene
          gltf.blender_scene = scene.name
          if bpy.context.collection.name in bpy.data.collections: # avoid master collection
              gltf.blender_active_collection = bpy.context.collection.name
          if scene.render.engine not in ['CYCLES', 'BLENDER_EEVEE']:
              scene.render.engine = "BLENDER_EEVEE"
  
          if gltf.data.scene is not None:
              import_user_extensions('gather_import_scene_before_hook', gltf, gltf.data.scenes[gltf.data.scene], scene)
              pyscene = gltf.data.scenes[gltf.data.scene]
              set_extras(scene, pyscene.extras)
  
          compute_vnodes(gltf)
  
          gltf.display_current_node = 0  # for debugging
          BlenderNode.create_vnode(gltf, 'root')
  
          # User extensions before scene creation
          import_user_extensions('gather_import_scene_after_nodes_hook', gltf, gltf.data.scenes[gltf.data.scene], scene)
  
          # User extensions after scene creation
          BlenderScene.create_animations(gltf)
  
          import_user_extensions('gather_import_scene_after_animation_hook', gltf, gltf.data.scenes[gltf.data.scene], scene)
  
          if bpy.context.mode != 'OBJECT':
              bpy.ops.object.mode_set(mode='OBJECT')
          BlenderScene.select_imported_objects(gltf)
          BlenderScene.set_active_object(gltf)
  
      @staticmethod
      def create_animations(gltf):
          """Create animations."""
          if gltf.data.animations:
              # NLA tracks are added bottom to top, so create animations in
              # reverse so the first winds up on top
              for anim_idx in reversed(range(len(gltf.data.animations))):
                  BlenderAnimation.anim(gltf, anim_idx)
  
              # Restore first animation
              anim_name = gltf.data.animations[0].track_name
              BlenderAnimation.restore_animation(gltf, anim_name)
  
      @staticmethod
      def select_imported_objects(gltf):
          """Select all (and only) the imported objects."""
          if bpy.ops.object.select_all.poll():
             bpy.ops.object.select_all(action='DESELECT')
  
          for vnode in gltf.vnodes.values():
              if vnode.type == VNode.Object:
                  vnode.blender_object.select_set(state=True)
  
      @staticmethod
      def set_active_object(gltf):
          """Make the first root object from the default glTF scene active.
          If no default scene, use the first scene, or just any root object.
          """
          vnode = None
  
          if gltf.data.scene is not None:
              pyscene = gltf.data.scenes[gltf.data.scene]
              if pyscene.nodes:
                  vnode = gltf.vnodes[pyscene.nodes[0]]
  
          if not vnode:
              for pyscene in gltf.data.scenes or []:
                  if pyscene.nodes:
                      vnode = gltf.vnodes[pyscene.nodes[0]]
                      break
  
          if not vnode:
              vnode = gltf.vnodes['root']
              if vnode.type == VNode.DummyRoot:
                  if not vnode.children:
                      return  # no nodes
                  vnode = gltf.vnodes[vnode.children[0]]
  
          if vnode.type == VNode.Bone:
              vnode = gltf.vnodes[vnode.bone_arma]
  
          bpy.context.view_layer.objects.active = vnode.blender_object
  