Code to allow users to create dark and light themes that are automatically applied when the OS color scheme changes

kitty/boss.py

@@ -36,6 +36,7 @@
     set_clipboard_string,
     set_primary_selection,
 )
+from .colors import ColorsSpec, TransparentBackgroundColors, patch_options_with_color_spec, theme_colors
 from .conf.utils import BadLine, KeyAction, to_cmdline
 from .config import common_opts_as_dict, prepare_config_file_for_editing
 from .constants import (
@@ -2637,10 +2638,9 @@ def disable_ligatures_in(self, where: Union[str, Iterable[Window]], strategy: in
             window.screen.disable_ligatures = strategy
             window.refresh()
 
-    def patch_colors(self, spec: dict[str, Optional[int]], transparent_background_colors: tuple[tuple[Color, float], ...], configured: bool = False) -> None:
+    def patch_colors(self, spec: ColorsSpec, transparent_background_colors: TransparentBackgroundColors, configured: bool = False) -> None:
         opts = get_options()
         if configured:
-            from kitty.colors import patch_options_with_color_spec
             patch_options_with_color_spec(opts, spec, transparent_background_colors)
         for tm in self.all_tab_managers:
             tm.tab_bar.patch_colors(spec)
@@ -3063,10 +3063,8 @@ def sanitize_url_for_dispay_to_user(self, url: str) -> str:
         return sanitize_url_for_dispay_to_user(url)
 
     def on_system_color_scheme_change(self, appearance: Literal['light', 'dark', 'no_preference'], is_initial_value: bool) -> None:
-        if is_initial_value:
-            pass
-        else:
-            log_error('system color theme changed:', appearance)
+        if not is_initial_value and appearance != 'no_preference':
+            theme_colors.on_system_color_scheme_change(appearance)
 
     @ac('win', '''
         Toggle to the tab matching the specified expression

kitty/colors.py

@@ -2,15 +2,71 @@
 # License: GPLv3 Copyright: 2024, Kovid Goyal <kovid at kovidgoyal.net>
 
 import os
-from typing import Iterable, Optional, Union
+from contextlib import suppress
+from typing import Iterable, Literal, Optional, Union
 
 from .config import parse_config
-from .fast_data_types import Color
+from .constants import config_dir
+from .fast_data_types import Color, get_boss, glfw_get_system_color_theme
 from .options.types import Options, nullable_colors
 from .rgb import color_from_int
 
+ColorsSpec = dict[str, Optional[int]]
+TransparentBackgroundColors = tuple[tuple[Color, float], ...]
 
-def parse_colors(args: Iterable[Union[str, Iterable[str]]]) -> tuple[dict[str, Optional[int]], tuple[tuple[Color, float], ...]]:
+
+class ThemeColors:
+
+    dark_mtime: float = -1
+    light_mtime: float = -1
+    applied_theme: Literal['light', 'dark', ''] = ''
+
+    def refresh(self) -> None:
+        with suppress(FileNotFoundError), open(os.path.join(config_dir, 'dark-theme.conf')) as f:
+            mtime = os.stat(f.fileno()).st_mtime
+            if mtime > self.dark_mtime:
+                self.dark_spec, self.dark_tbc = parse_colors((f,))
+                self.dark_mtime = mtime
+        with suppress(FileNotFoundError), open(os.path.join(config_dir, 'light-theme.conf')) as f:
+            mtime = os.stat(f.fileno()).st_mtime
+            if mtime > self.light_mtime:
+                self.light_spec, self.light_tbc = parse_colors((f,))
+                self.light_mtime = mtime
+
+    @property
+    def has_dark_theme(self) -> bool:
+        return self.dark_mtime > -1
+
+    @property
+    def has_light_theme(self) -> bool:
+        return self.light_mtime > -1
+
+    def patch_opts(self, opts: Options) -> None:
+        which = glfw_get_system_color_theme()
+        if which == 'dark' and self.has_dark_theme:
+            patch_options_with_color_spec(opts, self.dark_spec, self.dark_tbc)
+            self.applied_theme = 'dark'
+        elif which == 'light' and self.has_light_theme:
+            patch_options_with_color_spec(opts, self.light_spec, self.light_tbc)
+            self.applied_theme = 'light'
+
+    def on_system_color_scheme_change(self, new_value: Literal['light', 'dark']) -> bool:
+        boss = get_boss()
+        if new_value == 'dark' and self.has_dark_theme:
+            boss.patch_colors(self.dark_spec, self.dark_tbc, True)
+            self.applied_theme = 'dark'
+            return True
+        if new_value == 'light' and self.has_light_theme:
+            boss.patch_colors(self.light_spec, self.light_tbc, True)
+            self.applied_theme = 'light'
+            return True
+        return False
+
+
+theme_colors = ThemeColors()
+
+
+def parse_colors(args: Iterable[Union[str, Iterable[str]]]) -> tuple[ColorsSpec, TransparentBackgroundColors]:
     colors: dict[str, Optional[Color]] = {}
     nullable_color_map: dict[str, Optional[int]] = {}
     transparent_background_colors = ()
@@ -35,7 +91,7 @@ def parse_colors(args: Iterable[Union[str, Iterable[str]]]) -> tuple[dict[str, O
     return ans, transparent_background_colors
 
 
-def patch_options_with_color_spec(opts: Options, spec: dict[str, Optional[int]], transparent_background_colors: tuple[tuple[Color, float], ...]) -> None:
+def patch_options_with_color_spec(opts: Options, spec: ColorsSpec, transparent_background_colors: TransparentBackgroundColors) -> None:
 
     for k, v in spec.items():
         if hasattr(opts, k):

kitty/main.py

@@ -14,6 +14,7 @@
 from .child import set_default_env, set_LANG_in_default_env
 from .cli import create_opts, parse_args
 from .cli_stub import CLIOptions
+from .colors import theme_colors
 from .conf.utils import BadLine
 from .config import cached_values_for
 from .constants import (
@@ -248,6 +249,8 @@ def __init__(self) -> None:
     def __call__(self, opts: Options, args: CLIOptions, bad_lines: Sequence[BadLine] = (), talk_fd: int = -1) -> None:
         set_scale(opts.box_drawing_scale)
         set_options(opts, is_wayland(), args.debug_rendering, args.debug_font_fallback)
+        theme_colors.refresh()
+        theme_colors.patch_opts(opts)
         try:
             set_font_family(opts, add_builtin_nerd_font=True)
             _run_app(opts, args, bad_lines, talk_fd)