Simplify enabling VT100 mode on Windows.

Arguably, this relies on a bug, but: * The current implementation was vulnerable to platform-specific bugs, as highlighted in discussions of VT100 on Windows in the Python bug tracker, while the new one is clearly not going to cause harm. * If the bug in Python is fixed, hopefully we will gain a proper way to enable VT100.

Author: aaugustin

src/websockets/__main__.py

@@ -9,46 +9,14 @@
 
 try:
  import readline # noqa: F401
-except ImportError: # Windows has no `readline` normally
+except ImportError: # readline isn't available on all platforms
  pass
 
 from .frames import Close
 from .sync.client import ClientConnection, connect
 from .version import version as websockets_version
 
 
-if sys.platform == "win32":
-
- def win_enable_vt100() -> None:
- """
- Enable VT-100 for console output on Windows.
-
- See also https://github.com/python/cpython/issues/73245.
-
- """
- import ctypes
-
- STD_OUTPUT_HANDLE = ctypes.c_uint(-11)
- INVALID_HANDLE_VALUE = ctypes.c_uint(-1)
- ENABLE_VIRTUAL_TERMINAL_PROCESSING = 0x004
-
- handle = ctypes.windll.kernel32.GetStdHandle(STD_OUTPUT_HANDLE)
- if handle == INVALID_HANDLE_VALUE:
- raise RuntimeError("unable to obtain stdout handle")
-
- cur_mode = ctypes.c_uint()
- if ctypes.windll.kernel32.GetConsoleMode(handle, ctypes.byref(cur_mode)) == 0:
- raise RuntimeError("unable to query current console mode")
-
- # ctypes ints lack support for the required bit-OR operation.
- # Temporarily convert to Py int, do the OR and convert back.
- py_int_mode = int.from_bytes(cur_mode, sys.byteorder)
- new_mode = ctypes.c_uint(py_int_mode | ENABLE_VIRTUAL_TERMINAL_PROCESSING)
-
- if ctypes.windll.kernel32.SetConsoleMode(handle, new_mode) == 0:
- raise RuntimeError("unable to set console mode")
-
-
 def print_during_input(string: str) -> None:
  sys.stdout.write(
  # Save cursor position
@@ -116,17 +84,10 @@ def main() -> None:
  if args.uri is None:
  parser.error("the following arguments are required: <uri>")
 
- # If we're on Windows, enable VT100 terminal support.
- if sys.platform == "win32":
- try:
- win_enable_vt100()
- except RuntimeError as exc:
- sys.stderr.write(
- f"Unable to set terminal to VT100 mode. This is only "
- f"supported since Win10 anniversary update. Expect "
- f"weird symbols on the terminal.\nError: {exc}\n"
- )
- sys.stderr.flush()
+ # Enable VT100 to support ANSI escape codes in Command Prompt on Windows.
+ # See https://github.com/python/cpython/issues/74261 for why this works.
+ if sys.platform == "win32": # pragma: no cover
+ os.system("")
 
  try:
  websocket = connect(args.uri)