Init

ptlinux/desktop_entry.py

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+"""Install a desktop entry that does not depend on the GUI session's PATH."""
+
+from __future__ import annotations
+
+import argparse
+import os
+from pathlib import Path
+import sys
+from typing import Sequence
+
+
+EXECUTABLE_TOKEN = "@PTLINUX_EXECUTABLE@"
+ICON_TOKEN = "@PTLINUX_ICON@"
+
+
+class DesktopEntryError(ValueError):
+	"""Raised when a safe desktop entry cannot be rendered."""
+
+
+def quote_exec_argument(value: str) -> str:
+	"""Quote one Desktop Entry ``Exec`` argument without field-code expansion."""
+
+	if not value or any(character in value for character in ("\x00", "\n", "\r")):
+		raise DesktopEntryError("desktop executable path contains invalid characters")
+	escaped = value.replace("\\", "\\\\\\\\")
+	escaped = escaped.replace('"', '\\\\"')
+	escaped = escaped.replace("`", "\\\\`")
+	escaped = escaped.replace("$", "\\\\$")
+	escaped = escaped.replace("%", "%%")
+	return f'"{escaped}"'
+
+
+def escape_icon_path(value: str) -> str:
+	"""Escape one absolute Desktop Entry ``Icon`` path as a string value."""
+
+	if not value or any(character in value for character in ("\x00", "\n", "\r")):
+		raise DesktopEntryError("desktop icon path contains invalid characters")
+	return value.replace("\\", "\\\\")
+
+
+def render_desktop_entry(template: str, executable: Path, icon: Path) -> str:
+	"""Replace launcher and icon tokens with validated absolute paths."""
+
+	if template.count(EXECUTABLE_TOKEN) != 1:
+		raise DesktopEntryError("desktop template must contain exactly one executable token")
+	if template.count(ICON_TOKEN) != 1:
+		raise DesktopEntryError("desktop template must contain exactly one icon token")
+	launcher = executable.expanduser()
+	if not launcher.is_absolute():
+		raise DesktopEntryError("desktop launcher path must be absolute")
+	if not launcher.is_file() or not os.access(launcher, os.X_OK):
+		raise DesktopEntryError(f"desktop launcher is missing or not executable: {launcher}")
+	icon_path = icon.expanduser()
+	if not icon_path.is_absolute():
+		raise DesktopEntryError("desktop icon path must be absolute")
+	if not icon_path.is_file():
+		raise DesktopEntryError(f"desktop icon is missing: {icon_path}")
+	rendered = template.replace(EXECUTABLE_TOKEN, quote_exec_argument(str(launcher)))
+	rendered = rendered.replace(ICON_TOKEN, escape_icon_path(str(icon_path)))
+	return rendered if rendered.endswith("\n") else rendered + "\n"
+
+
+def install_desktop_entry(
+	template: Path,
+	executable: Path,
+	icon: Path,
+	destination: Path,
+) -> None:
+	"""Render and atomically install one user-level desktop entry."""
+
+	rendered = render_desktop_entry(
+		template.read_text(encoding="utf-8"),
+		executable,
+		icon,
+	)
+	destination.parent.mkdir(parents=True, exist_ok=True)
+	temporary = destination.with_name(f".{destination.name}.{os.getpid()}.tmp")
+	try:
+		temporary.write_text(rendered, encoding="utf-8")
+		temporary.chmod(0o644)
+		temporary.replace(destination)
+	except BaseException:
+		temporary.unlink(missing_ok=True)
+		raise
+
+
+def main(argv: Sequence[str] | None = None) -> int:
+	parser = argparse.ArgumentParser(description="install the PristonTale EU desktop entry")
+	parser.add_argument("template", type=Path)
+	parser.add_argument("executable", type=Path)
+	parser.add_argument("icon", type=Path)
+	parser.add_argument("destination", type=Path)
+	arguments = parser.parse_args(argv)
+	try:
+		install_desktop_entry(
+			arguments.template,
+			arguments.executable,
+			arguments.icon,
+			arguments.destination,
+		)
+	except (DesktopEntryError, OSError) as exc:
+		print(f"Could not install desktop shortcut: {exc}", file=sys.stderr)
+		return 1
+	return 0
+
+
+if __name__ == "__main__":
+	raise SystemExit(main())