add tests for dark theme and mode

prettypretty/darkmode.py

@@ -0,0 +1,125 @@
+import os
+import sys
+
+from .color.conversion import get_converter
+from .color.theme import current_theme
+
+
+def is_dark_theme() -> bool:
+    """
+    Determine whether the current terminal theme is a dark theme. This function
+    converts the default foreground and background colors of the current theme
+    to the XYZ color space and then compares their Y, that is, luminance,
+    components. If foreground has has higher luminance than the background, the
+    terminal is using a dark therme.
+    """
+    theme = current_theme()
+
+    # Convert to XYZ
+    foreground_xyz = get_converter(theme.text.tag, 'xyz')(*theme.text.coordinates)
+    background_xyz = get_converter(theme.background.tag, 'xyz')(
+        *theme.background.coordinates
+    )
+
+    # Compare luminance components
+    return foreground_xyz[1] > background_xyz[1]
+
+
+def is_dark_mode() -> None | bool:
+    """
+    Determine whether the operating system is in dark mode.
+
+    Returns:
+        ``True`` for dark mode, ``False`` for light mode, and ``None`` if the
+        mode could not be determined.
+
+    The implementation builds on answers to [this StackOverflow
+    question](https://stackoverflow.com/questions/65294987/detect-os-dark-mode-in-python)
+    and [the darkdetect package](https://github.com/albertosottile/darkdetect).
+    The latter seems both over- and under-engineered. In contrast, this module
+    provides the one interesting bit, whether the system is in dark mode, if
+    available and nothing else.
+    """
+    try:
+        if sys.platform == "darwin":
+            return _is_darkmode_macos()
+        elif sys.platform == "linux":
+            return _is_darkmode_linux()
+        elif os.name == 'nt':
+            return _is_darkmode_windows()
+        else:
+            return None
+    except:
+        return None
+
+
+def _is_darkmode_windows() -> bool:
+    import winreg
+
+    with winreg.OpenKey(  # type: ignore[attr-defined]
+        winreg.HKEY_CURRENT_USER,  # type: ignore[attr-defined]
+        "Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize",
+    ) as key:  # type: ignore
+        return not winreg.QueryValueEx(  # type: ignore[attr-defined]
+            key, "AppsUseLightTheme"
+        )[0]
+
+
+def _is_darkmode_macos() -> bool:
+    import subprocess
+
+    # Use DEVNULL so that output of command isn't shown
+    return not subprocess.run(
+        ["defaults", "read", "-g", "AppleInterfaceStyle"],
+        stdout=subprocess.DEVNULL,
+        stderr=subprocess.DEVNULL,
+    ).returncode
+
+
+def _is_darkmode_linux() -> None | bool:
+    import subprocess
+
+    try:
+        result = subprocess.run( [
+                "dbus-send",
+                "--session",
+                "--print-reply=literal",
+                "--dest=org.freedesktop.portal.Desktop",
+                "/org/freedesktop/portal/desktop",
+                "org.freedesktop.portal.Settings.Read",
+                "string:org.freedesktop.appearance",
+                "string:color-scheme"
+            ],
+            capture_output=True,
+            encoding='utf8',
+            check=True,
+        )
+
+        stdout = result.stdout.replace("variant", "").replace("uint32", "").strip()
+        if stdout in ("0", "1", "2"):
+            # 0 stands for default, 1 for prefers-dark, and 2 for prefers-light.
+            # Ubuntu returns 0 for light mode and 1 for dark mode.
+            return stdout == "1"
+    except:
+        pass
+
+    try:
+        result = subprocess.run(
+            ["gsettings", "get", "org.gnome.desktop.interface", "color-scheme"],
+            capture_output=True,
+            encoding="utf8",
+            check=True,
+        )
+        stdout = result.stdout.strip()
+    except:
+        stdout = ""
+
+    if not stdout:
+        result = subprocess.run(
+            ["gsettings", "get", "org.gnome.desktop.interface", "gtk-theme"],
+            capture_output=True,
+            encoding="utf8",
+            check=True,
+        )
+        stdout = result.stdout.strip()
+    return stdout.strip("'").endswith("-dark")