object_print3d_utils: switch 3D Print Toolbox obj export to use the new exporter

The 3D Print Toolbox addon was using the Python based exporter API,
switch it to use the C++ based obj exporter. This is faster, supports
vertex color attributes, and allows to remove the Python based exporter
some day.

Reviewed By: Campbell Barton
Differential Revision: https://developer.blender.org/D15769

object_print3d_utils/export.py

@@ -134,17 +134,17 @@ def write_mesh(context, report_cb):
             use_normals=export_data_layers,
         )
     elif export_format == 'OBJ':
-        addon_ensure("io_scene_obj")
         filepath = bpy.path.ensure_ext(filepath, ".obj")
-        ret = bpy.ops.export_scene.obj(
+        ret = bpy.ops.wm.obj_export(
             filepath=filepath,
-            use_mesh_modifiers=True,
-            use_selection=True,
-            global_scale=global_scale,
+            apply_modifiers=True,
+            export_selected_objects=True,
+            scaling_factor=global_scale,
             path_mode=path_mode,
-            use_normals=export_data_layers,
-            use_uvs=export_data_layers,
-            use_materials=export_data_layers,
+            export_normals=export_data_layers,
+            export_uv=export_data_layers,
+            export_materials=export_data_layers,
+            export_colors=export_data_layers,
         )
     else:
         assert 0