scc: change SccCode class hierarchy to fix incompatibility with Pytho…

…n 3.11 (#386)

Bump ubuntu version on CI

.github/workflows/main.yml

@@ -4,17 +4,17 @@ on: [push, pull_request]
 
 jobs:
   run:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     if: github.event_name == 'push' || (github.event_name == 'pull_request' && github.event.pull_request.head.repo.full_name != github.repository)
     steps:
-    - name: Install dependencies
-      run: |
-        sudo apt-get update
-        sudo apt-get -y install python3.7 python3-pip
-        sudo update-alternatives --install /usr/bin/python python /usr/bin/python3 10
-        sudo update-alternatives --install /usr/bin/pip pip /usr/bin/pip3 10
-        python3.7 -m pip install pipenv
-        
+
+    - uses: actions/setup-python@v4
+      with:
+        python-version: '3.7'
+
+    - name: Initialize pip environment
+      run: python -m pip install pipenv
+
     - name: Checkout repo
       uses: actions/checkout@v2
       with:

.pylintrc

@@ -421,7 +421,7 @@ contextmanager-decorators=contextlib.contextmanager
 # List of members which are set dynamically and missed by pylint inference
 # system, and so shouldn't trigger E1101 when accessed. Python regular
 # expressions are accepted.
-generated-members=
+generated-members=SccAttributeCode.BMS.value
 
 # Tells whether missing members accessed in mixin class should be ignored. A
 # mixin class is detected if its name ends with "mixin" (case insensitive).

src/main/python/ttconv/scc/codes/__init__.py

@@ -25,6 +25,8 @@
 
 """SCC Codes"""
 
+from enum import Enum
+from typing import Tuple
 from ttconv.style_properties import NamedColors
 
 SCC_COLOR_MAPPING = {
@@ -45,7 +47,7 @@
 }
 
 
-class SccCode:
+class SccCode(Enum):
   """SCC codes base definition class"""
 
   def __init__(self, channel_1: int, channel_2: int):
@@ -55,7 +57,7 @@ def __init__(self, channel_1: int, channel_2: int):
     self._channel_1 = channel_1
     self._channel_2 = channel_2
 
-  def get_values(self) -> (int, int):
+  def get_values(self) -> Tuple[int, int]:
     """Returns SCC Code values"""
     return self._channel_1, self._channel_2
 

src/main/python/ttconv/scc/codes/attribute_codes.py

@@ -27,14 +27,13 @@
 
 from __future__ import annotations
 
-from enum import Enum
 from typing import Optional
 
 from ttconv.scc.codes import SccCode
 from ttconv.style_properties import ColorType, NamedColors, TextDecorationType
 
 
-class SccAttributeCode(SccCode, Enum):
+class SccAttributeCode(SccCode):
   """SCC Foreground and Background Attribute Codes definition"""
   BWO = (0x1020, 0x1820, ColorType((0xFF, 0xFF, 0xFF, 0xFF)))  # Background White, Opaque
   BWS = (0x1021, 0x1821, ColorType((0xFF, 0xFF, 0xFF, 0x88)))  # Background White, Semi-transparent

src/main/python/ttconv/scc/codes/control_codes.py

@@ -28,12 +28,11 @@
 from __future__ import annotations
 
 import typing
-from enum import Enum
 
 from ttconv.scc.codes import SccCode
 
 
-class SccControlCode(SccCode, Enum):
+class SccControlCode(SccCode):
   """SCC Control Code definition"""
   AOF = (0x1422, 0x1C22, 0x1522, 0x1D22)  # Reserved (formerly Alarm Off)
   AON = (0x1423, 0x1C23, 0x1523, 0x1D23)  # Reserved (formerly Alarm On)
@@ -64,7 +63,7 @@ def get_name(self) -> str:
     """Retrieves Control Code name"""
     return self.name
 
-  def get_values(self) -> (int, int, int, int):
+  def get_values(self) -> typing.Tuple[int, int, int, int]:
     """Returns SCC Control Code values"""
     return self._channel_1, self._channel_2, self._channel_1_field_2, self._channel_2_field_2
 

src/main/python/ttconv/scc/codes/mid_row_codes.py

@@ -28,13 +28,12 @@
 from __future__ import annotations
 
 import typing
-from enum import Enum
 
 from ttconv.scc.codes import SccCode, SCC_COLOR_MAPPING
 from ttconv.style_properties import FontStyleType, TextDecorationType, ColorType
 
 
-class SccMidRowCode(SccCode, Enum):
+class SccMidRowCode(SccCode):
   """SCC Mid-Row Code values"""
   WHITE = (0x1120, 0x1920)
   WHITE_UNDERLINE = (0x1121, 0x1921)

src/main/python/ttconv/scc/codes/special_characters.py

@@ -28,12 +28,11 @@
 from __future__ import annotations
 
 import typing
-from enum import Enum
 
 from ttconv.scc.codes import SccCode
 
 
-class SccSpecialCharacter(SccCode, Enum):
+class SccSpecialCharacter(SccCode):
   """SCC Special character definition"""
 
   # Special characters specified in CEA-608
@@ -71,7 +70,7 @@ def find(value: int) -> typing.Optional[SccSpecialCharacter]:
     return None
 
 
-class SccExtendedCharacter(SccCode, Enum):
+class SccExtendedCharacter(SccCode):
   """SCC Extended character definition"""
 
   # Spanish extended characters

src/main/python/ttconv/scc/reader.py

@@ -29,7 +29,7 @@
 
 import copy
 import logging
-from typing import Optional
+from typing import Optional, Tuple
 
 from ttconv.model import ContentDocument, Body, Div, CellResolutionType, ActiveAreaType
 from ttconv.scc.codes.attribute_codes import SccAttributeCode
@@ -76,7 +76,7 @@ def __init__(self, config: Optional[SccReaderConfiguration] = None):
     self.roll_up_depth: int = 0
 
     # Cursor position in the active area
-    self.active_cursor: (int, int) = (0, 0)
+    self.active_cursor: Tuple[int, int] = (0, 0)
 
     self.current_text_decoration = None
     self.current_color = None