support for color theme plugins

khal/plugins.py

@@ -1,4 +1,5 @@
 from collections.abc import Callable, Mapping
+from typing import Tuple
 
 from khal._compat import importlib_metadata
 
@@ -18,6 +19,12 @@ def _load_formatters() -> dict[str, Callable[[str, str], str]]:
 
 FORMATTERS: Mapping[str, Callable[[str, str], str]] = _load_formatters()
 
+def _load_color_themes() -> dict[str, Mapping[str, Tuple[str, str, str, str, str]]]:
+    color_theme_entrypoints = importlib_metadata.entry_points(group="khal.color_theme")
+    return {ep.name: ep.load() for ep in color_theme_entrypoints}
+
+THEMES: Mapping[str, Mapping[str, dict[str, Tuple[str, str, str, str, str]]]] = _load_color_themes()
+
 # class ParserExtensionInterface(Protocol):
 #     """An interface for parser extension plugins."""
 

khal/settings/khal.spec

@@ -258,7 +258,7 @@ blank_line_before_day = boolean(default=False)
 #
 # __ http://urwid.org/manual/displayattributes.html
 # .. _github: https://github.com/pimutils/khal/issues
-theme = option('dark', 'light', default='dark')
+theme = string(default='dark')
 
 # Whether to show a visible frame (with *box drawing* characters) around some
 # (groups of) elements or not. There are currently several different frame

khal/ui/__init__.py

@@ -30,8 +30,9 @@
 import urwid
 
 from .. import utils
+from .. import plugins
 from ..khalendar import CalendarCollection
-from ..khalendar.exceptions import ReadOnlyCalendarError
+from ..khalendar.exceptions import FatalError, ReadOnlyCalendarError
 from . import colors
 from .base import Pane, Window
 from .editor import EventEditor, ExportDialog
@@ -1356,6 +1357,17 @@ def start_pane(
         color_mode: Literal['rgb', '256colors']='rgb',
 ):
     """Open the user interface with the given initial pane."""
+    # We don't validate the themes in settings.spec but instead here
+    # first try to load built-in themes, then try to load themes from
+    # plugins
+    theme = colors.themes.get(pane._conf['view']['theme'])
+    if theme is None:
+        theme = plugins.THEMES.get(pane._conf['view']['theme'])
+    if theme is None:
+        logger.fatal(f'Invalid theme {pane._conf["view"]["theme"]} configured')
+        logger.fatal(f'Available themes are: {", ".join(colors.themes.keys())}')
+        raise FatalError
+
     quit_keys = quit_keys or ['q']
 
     frame = Window(
@@ -1406,7 +1418,6 @@ def emit(self, record):
     logger.addHandler(header_handler)
 
     frame.open(pane, callback)
-    theme = getattr(colors, pane._conf['view']['theme'])
     palette = _add_calendar_colors(
         theme, pane.collection, color_mode=color_mode,
         base='calendar', attr_template='calendar {}',