1 files changed, 151 insertions, 0 deletions
diff --git a/auto_xsettingsd.py b/auto_xsettingsd.py
new file mode 100644
index 0000000..b6acd36
--- /dev/null
+++ b/auto_xsettingsd.py
@@ -0,0 +1,151 @@
+"""Automatically update xsettings based on gsettings"""
+
+__version__ = "0.1.0"
+
+import os
+import signal
+import struct
+import sys
+import tempfile
+from collections.abc import Iterator
+from pathlib import Path
+from subprocess import Popen
+
+from gi.repository import Gio, GLib
+
+DESKTOP_INTERFACE_SCHEMA = "org.gnome.desktop.interface"
+GTK_THEME_KEY = "gtk-theme"
+HEADER_FORMAT = ">H"
+
+
+def start_gsettings_listener() -> tuple[int, int]:
+    def on_change(settings, key):
+        if settings.props.schema_id != DESKTOP_INTERFACE_SCHEMA:
+            return
+        if key != GTK_THEME_KEY:
+            return
+        gtk_theme = settings.get_string(key).encode()
+        data = struct.pack(HEADER_FORMAT, len(gtk_theme))
+        os.write(write, data + gtk_theme)
+
+    read, write = os.pipe()
+    os.set_inheritable(write, True)
+    pid = os.fork()
+    if pid != 0:
+        os.close(write)
+        return read, pid
+
+    settings = Gio.Settings.new(DESKTOP_INTERFACE_SCHEMA)
+    settings.connect("changed", on_change)
+    on_change(settings, GTK_THEME_KEY)
+
+    try:
+        GLib.MainLoop().run()
+        exit(1)
+    except KeyboardInterrupt:
+        os._exit(0)
+
+
+def start_xsettingsd(conf: str, args: list[str]) -> Popen:
+    return Popen(["xsettingsd", "--config", conf] + args)
+
+
+def read_theme(fd: int) -> str:
+    header = os.read(fd, 2)
+    (length,) = struct.unpack(HEADER_FORMAT, header)
+    return os.read(fd, length).decode()
+
+
+def xsettingsd_escape(s: str) -> str:
+    return s.replace("\n", r"\n").replace('"', r"\"")
+
+
+def get_xsettingsd_config_paths() -> Iterator[Path]:
+    yield Path.home() / ".xsettingsd"
+    conf_home = os.environ.get("XDG_CONFIG_HOME")
+    conf_home = Path(conf_home) if conf_home else Path.home() / ".config"
+    xdg_dirs = [conf_home]
+    conf_dirs = os.environ.get("XDG_CONFIG_DIRS")
+    if conf_dirs:
+        for d in conf_dirs.split(":"):
+            xdg_dirs.append(Path(d))
+    for d in xdg_dirs:
+        yield d / "xsettingsd" / "xsettingsd.conf"
+
+
+XSETTINGSD_CONFIG_PATHS = list(get_xsettingsd_config_paths())
+
+
+# It would make more sense to only read the config once every HUP
+def get_xsettingsd_config() -> str:
+    for path in XSETTINGSD_CONFIG_PATHS:
+        try:
+            with path.open() as f:
+                return f.read()
+        except FileNotFoundError:
+            pass
+    return ""
+
+
+def write_merged_settings(fd: int, gtk_theme: str) -> None:
+    os.lseek(fd, 0, os.SEEK_SET)
+    os.ftruncate(fd, 0)
+    os.write(fd, f'Net/ThemeName "{xsettingsd_escape(gtk_theme)}"\n'.encode())
+    os.write(fd, get_xsettingsd_config().encode())
+
+
+def start_reconfigurator(theme_fd: int, conf_fd: int, xsettingsd_pid: int) -> int:
+    os.set_inheritable(theme_fd, True)
+    os.set_inheritable(conf_fd, True)
+    pid = os.fork()
+    if pid != 0:
+        os.close(theme_fd)
+        return pid
+
+    try:
+        while True:
+            gtk_theme = read_theme(theme_fd)
+            write_merged_settings(conf_fd, gtk_theme)
+            os.kill(xsettingsd_pid, signal.SIGHUP)
+    except KeyboardInterrupt:
+        os._exit(0)
+
+
+def kill_and_wait(pid: int) -> None:
+    os.kill(pid, signal.SIGTERM)
+    os.kill(pid, signal.SIGCONT)
+    try:
+        os.waitpid(pid, 0)
+    except ChildProcessError as e:
+        print(e)
+        pass
+
+
+def main():
+    xsettingsd = None
+    gsettings_pid = None
+    reconf_pid = None
+    conf_fd, conf_name = tempfile.mkstemp(prefix="xsettings", suffix=".conf")
+    try:
+        notify_fd, gsettings_pid = start_gsettings_listener()
+        gtk_theme = read_theme(notify_fd)
+        write_merged_settings(conf_fd, gtk_theme)
+        xsettingsd = start_xsettingsd(conf_name, sys.argv[1:])
+        reconf_pid = start_reconfigurator(notify_fd, conf_fd, xsettingsd.pid)
+        pid, _ = os.wait()
+    except KeyboardInterrupt:
+        pid = None
+        pass
+    finally:
+        os.close(conf_fd)
+        os.unlink(conf_name)
+    if xsettingsd and pid != xsettingsd.pid:
+        xsettingsd.terminate()
+    if gsettings_pid and pid != gsettings_pid:
+        kill_and_wait(gsettings_pid)
+    if reconf_pid and pid != reconf_pid:
+        kill_and_wait(reconf_pid)
+
+
+if __name__ == "__main__":
+    main()