Implemented reporting callbacks.

Both the dependency Tracer class and the Packer class now support a
callback object, where the latter is a subclass of the former.

For file transfers running in a separate thread, there is a thread-safe
wrapper for progress callbacks. This wrapper can be called from any thread,
and calls the wrapped callback object from the main thread. This way the
callback implementation itself doesn't have to worry about threading
issues.

blender_asset_tracer/trace/file2blocks.py

@@ -11,13 +11,13 @@ import pathlib
 import typing
 
 from blender_asset_tracer import blendfile, bpathlib
-from . import expanders
+from . import expanders, progress
 
 _funcs_for_code = {}  # type: typing.Dict[bytes, typing.Callable]
 log = logging.getLogger(__name__)
 
 
-class _BlockIterator:
+class BlockIterator:
     """Expand blocks with dependencies from other libraries.
 
     This class exists so that we have some context for the recursive expansion
@@ -31,12 +31,15 @@ class _BlockIterator:
         # Queue of blocks to visit
         self.to_visit = collections.deque()  # type: typing.Deque[blendfile.BlendFileBlock]
 
+        self.progress_cb = progress.Callback()
+
     def iter_blocks(self,
                     bfile: blendfile.BlendFile,
                     limit_to: typing.Set[blendfile.BlendFileBlock] = set(),
                     ) -> typing.Iterator[blendfile.BlendFileBlock]:
         """Expand blocks with dependencies from other libraries."""
 
+        self.progress_cb.trace_blendfile(bfile.filepath)
         log.info('inspecting: %s', bfile.filepath)
         if limit_to:
             self._queue_named_blocks(bfile, limit_to)
@@ -148,5 +151,5 @@ class _BlockIterator:
 
 def iter_blocks(bfile: blendfile.BlendFile) -> typing.Iterator[blendfile.BlendFileBlock]:
     """Generator, yield all blocks in this file + required blocks in libs."""
-    bi = _BlockIterator()
+    bi = BlockIterator()
     yield from bi.iter_blocks(bfile)