Refactor config (#340)

* add a context manager to temporarily change the global config. This will be useful for testing

* make Camera instances read some of their values from the global config dict at construction, and not when the Camera class is defined as it was previously done

* update test_logging to use the correct expected.txt file

Author: leotrs

manim/__init__.py

@@ -1,12 +1,11 @@
 #!/usr/bin/env python
 
-
 # Importing the config module should be the first thing we do, since other
 # modules depend on the global config dict for initialization.  Note that the
 # global config dict is called 'config', just like the module itself.  That's
 # why we import the module first with a different name, and then the dict.
 from . import config as _config
-from .config import config
+from .config import config, tempconfig
 
 from .constants import *
 

manim/camera/camera.py

@@ -44,19 +44,13 @@ class Camera(object):
 
     CONFIG = {
         "background_image": None,
-        "pixel_height": config["pixel_height"],
-        "pixel_width": config["pixel_width"],
-        "frame_rate": config["frame_rate"],
         # Note: frame height and width will be resized to match
         # the pixel aspect ratio
-        "frame_height": config["frame_height"],
-        "frame_width": config["frame_width"],
         "frame_center": ORIGIN,
         "background_color": BLACK,
         "background_opacity": 1,
         # Points in vectorized mobjects with norm greater
         # than this value will be rescaled.
-        "max_allowable_norm": config["frame_width"],
         "image_mode": "RGBA",
         "n_channels": 4,
         "pixel_array_dtype": "uint8",
@@ -78,6 +72,26 @@ def __init__(self, background=None, **kwargs):
             Any local variables to be set.
         """
         digest_config(self, kwargs, locals())
+
+        # All of the following are set to EITHER the value passed via kwargs,
+        # OR the value stored in the global config dict at the time of
+        # _instance construction_.  Before, they were in the CONFIG dict, which
+        # is a class attribute and is defined at the time of _class
+        # definition_.  This did not allow for creating two Cameras with
+        # different configurations in the same session.
+        for attr in [
+            "pixel_height",
+            "pixel_width",
+            "frame_height",
+            "frame_width",
+            "frame_rate",
+        ]:
+            setattr(self, attr, kwargs.get(attr, config[attr]))
+
+        # This one is in the same boat as the above, but it doesn't have the
+        # same name as the corresponding key so it has to be handled on its own
+        self.max_allowable_norm = config["frame_width"]
+
         self.rgb_max_val = np.iinfo(self.pixel_array_dtype).max
         self.pixel_array_to_cairo_context = {}
 

manim/config.py

@@ -6,6 +6,7 @@
 """
 import os
 import sys
+from contextlib import contextmanager
 
 import colour
 
@@ -15,7 +16,55 @@
 from .logger import logger
 from .utils.tex import TexTemplate, TexTemplateFromFile
 
-__all__ = ["file_writer_config", "config", "camera_config"]
+__all__ = ["file_writer_config", "config", "camera_config", "tempconfig"]
+
+
+config = None
+
+
+@contextmanager
+def tempconfig(temp):
+    """Context manager that temporarily modifies the global config dict.
+
+    The code block inside the ``with`` statement will use the modified config.
+    After the code block, the config will be restored to its original value.
+
+    Parameters
+    ----------
+
+    temp : :class:`dict`
+        A dictionary whose keys will be used to temporarily update the global
+        config.
+
+    Examples
+    --------
+    Use ``with tempconfig({...})`` to temporarily change the default values of
+    certain objects.
+
+    .. code_block:: python
+
+       c = Camera()
+       c.frame_width == config['frame_width']        # -> True
+       with tempconfig({'frame_width': 100}):
+           c = Camera()
+           c.frame_width == config['frame_width']    # -> False
+           c.frame_width == 100                      # -> True
+
+    """
+    global config
+    original = config.copy()
+
+    temp = {k: v for k, v in temp.items() if k in original}
+
+    # In order to change the config that every module has acces to, use
+    # update(), DO NOT use assignment.  Assigning config = some_dict will just
+    # make the local variable named config point to a new dictionary, it will
+    # NOT change the dictionary that every module has a reference to.
+    config.update(temp)
+    try:
+        yield
+    finally:
+        config.update(original)  # update, not assignment!
 
 
 def _parse_config(config_parser, args):

tests/test_camera.py

@@ -0,0 +1,16 @@
+import pytest
+from manim import Camera, tempconfig, config
+
+
+def test_camera():
+    """Test that Camera instances initialize to the correct config."""
+    # by default, use the config
+    assert Camera().frame_width == config["frame_width"]
+    # init args override config
+    assert Camera(frame_width=10).frame_width == 10
+
+    # if config changes, reflect those changes
+    with tempconfig({"frame_width": 100}):
+        assert Camera().frame_width == 100
+        # ..init args still override new config
+        assert Camera(frame_width=10).frame_width == 10

tests/test_config.py

@@ -0,0 +1,29 @@
+import pytest
+import numpy as np
+from manim import config, tempconfig
+
+
+def test_tempconfig():
+    """Test the tempconfig context manager."""
+    original = config.copy()
+
+    with tempconfig({"frame_width": 100, "frame_height": 42, "foo": -1}):
+        # check that config was modified correctly
+        assert config["frame_width"] == 100
+        assert config["frame_height"] == 42
+
+        # 'foo' is not a key in the original dict so it shouldn't be added
+        assert "foo" not in config
+
+        # check that no keys are missing and no new keys were added
+        assert set(original.keys()) == set(config.keys())
+
+    # check that the keys are still untouched
+    assert set(original.keys()) == set(config.keys())
+
+    # check that config is correctly restored
+    for k, v in original.items():
+        if isinstance(v, np.ndarray):
+            assert np.allclose(config[k], v)
+        else:
+            assert config[k] == v

tests/test_logging/expected.txt

@@ -1,4 +1,4 @@
-DEBUG     Read configuration files:                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 config.py:  
+DEBUG     Read configuration files:                                                                                                                                                                                                                                                                                                                                                                                                                                                                                config.py:   
 DEBUG     Animation   : Partial movie file written in                                                                                                                                                                                                                                                                                                                                                                                                                                                   scene_file_writer.py:   
 DEBUG     Animation   : Partial movie file written in                                                                                                                                                                                                                                                                                                                                                                                                                                                   scene_file_writer.py:   
 DEBUG     Animation   : Partial movie file written in                                                                                                                                                                                                                                                                                                                                                                                                                                                   scene_file_writer.py: