glTF importer: Implement a user extension system

2 files changed, 31 insertions, 0 deletions

diff --git a/io_scene_gltf2/io/imp/gltf2_io_gltf.py b/io_scene_gltf2/io/imp/gltf2_io_gltf.py
index aa9bda38..407afccd 100755
--- a/io_scene_gltf2/io/imp/gltf2_io_gltf.py
+++ b/io_scene_gltf2/io/imp/gltf2_io_gltf.py
@@ -38,6 +38,7 @@ class glTFImporter():
         self.buffers = {}
         self.accessor_cache = {}
         self.decode_accessor_cache = {}
+        self.import_user_extensions = import_settings['import_user_extensions']
 
         if 'loglevel' not in self.import_settings.keys():
             self.import_settings['loglevel'] = logging.ERROR
@@ -57,6 +58,13 @@ class glTFImporter():
             'KHR_draco_mesh_compression'
         ]
 
+        # Add extensions required supported by custom import extensions
+        for import_extension in self.import_user_extensions:
+            if hasattr(import_extension, "extensions"):
+                for custom_extension in import_extension.extensions:
+                    if custom_extension.required:
+                        self.extensions_managed.append(custom_extension.name)
+
     @staticmethod
     def load_json(content):
         def bad_constant(val):
diff --git a/io_scene_gltf2/io/imp/gltf2_io_user_extensions.py b/io_scene_gltf2/io/imp/gltf2_io_user_extensions.py
new file mode 100644
index 00000000..0c439251
--- /dev/null
+++ b/io_scene_gltf2/io/imp/gltf2_io_user_extensions.py
@@ -0,0 +1,23 @@
+# 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.
+
+def import_user_extensions(hook_name, gltf_importer, *args):
+    for extension in gltf_importer.import_user_extensions:
+        hook = getattr(extension, hook_name, None)
+        if hook is not None:
+            try:
+                hook(*args, gltf_importer)
+            except Exception as e:
+                print(hook_name, "fails on", extension)
+                print(str(e))