POC: Implement Plugin using Hooks (with pluggy)

This uses pluggy to manage plugins, by implementing hooks, which
the plugins can implement to modify the default behaviour in Manim.
For now, there's only one hook `default_font()`, which plugins or even
the users can define.

REF: #1133

Author: naveen521kk

manim/__init__.py

@@ -10,6 +10,11 @@
 
 import sys
 
+import pluggy
+
+# This should be created before anything else.
+pluggy_hookimpl = pluggy.HookimplMarker("manim")
+
 # Importing the config module should be the first thing we do, since other
 # modules depend on the global config dict for initialization.
 from ._config import *

manim/_config/utils.py

@@ -25,6 +25,7 @@
 
 import colour
 import numpy as np
+import pluggy
 
 from .. import constants
 from ..utils.tex import TexTemplate, TexTemplateFromFile
@@ -300,6 +301,7 @@ class MyScene(Scene):
 
     def __init__(self) -> None:
         self._d = {k: None for k in self._OPTS}
+        self._plugin_manager = None
 
     # behave like a dict
     def __iter__(self) -> typing.Iterator[str]:
@@ -1570,6 +1572,19 @@ def plugins(self):
     def plugins(self, value):
         self._d["plugins"] = value
 
+    @property
+    def plugin_manager(self):
+        if self._plugin_manager:
+            return self._plugin_manager
+        from manim.plugins import hooksimpl, hookspecs
+
+        pm = pluggy.PluginManager("manim")
+        pm.add_hookspecs(hookspecs)
+        pm.load_setuptools_entrypoints("manim")
+        pm.register(hooksimpl)
+        self._plugin_manager = pm
+        return pm
+
 
 class ManimFrame(Mapping):
     _OPTS: set[str] = {

manim/cli/render/commands.py

@@ -17,7 +17,7 @@
 
 from ... import __version__, config, console, error_console, logger
 from ...constants import EPILOG
-from ...utils.module_ops import scene_classes_from_file
+from ...utils.module_ops import get_module, scene_classes_from_file
 from .ease_of_access_options import ease_of_access_options
 from .global_options import global_options
 from .output_options import output_options
@@ -88,6 +88,9 @@ def __repr__(self):
 
     config.digest_args(click_args)
     file = Path(config.input_file)
+    # Register the input file with Pluggy
+    # This is done so that user's implementation of hooks takes precedence.
+    config.plugin_manager.register(get_module(file))
     if config.renderer == "opengl":
         from manim.renderer.opengl_renderer import OpenGLRenderer
 

manim/mobject/text/text_mobject.py

@@ -409,7 +409,7 @@ def __init__(
         color: Color | str | None = None,
         font_size: float = DEFAULT_FONT_SIZE,
         line_spacing: float = -1,
-        font: str = "",
+        font: str | None = None,
         slant: str = NORMAL,
         weight: str = NORMAL,
         t2c: dict[str, str] = None,
@@ -429,6 +429,8 @@ def __init__(
     ):
 
         self.line_spacing = line_spacing
+        if not font:
+            font = config.plugin_manager.hook.default_font(requestor=Text.__name__)[0]
         self.font = font
         self._font_size = float(font_size)
         # needs to be a float or else size is inflated when font_size = 24

manim/plugins/hooksimpl.py

@@ -0,0 +1,9 @@
+from __future__ import annotations
+
+from manim import pluggy_hookimpl
+
+
+@pluggy_hookimpl
+def default_font() -> str:
+    # Returning empty string, just uses the default font.
+    return ""

manim/plugins/hookspecs.py

@@ -0,0 +1,23 @@
+from __future__ import annotations
+
+import pluggy
+
+hookspec = pluggy.HookspecMarker("manim")
+
+
+@hookspec
+def default_font(requestor: str) -> str:
+    """Look who's requesting and return the default font to be used by
+    them.
+
+    Parameters
+    ----------
+    requestor:
+        The ``__name__`` of the requesting class. This can be one of
+        ['Text', 'MarkupText', 'Paragraph', 'Code']
+
+    Returns
+    -------
+    str:
+        Can be empty string to use the default font as defined by the system.
+    """

poetry.lock

@@ -55,6 +55,7 @@ srt = "^3.5.0"
 screeninfo = "^0.8"
 Pygments = "^2.10.0"
 "backports.cached-property" = "^1.0.1"
+pluggy = "^1"
 
 [tool.poetry.extras]
 jupyterlab = ["jupyterlab"]