Erratic ValueError raised in get_power_mode()

[gabortim]

• Monitor manufacturer and model number: Dell U2415
• Input source (HDMI, VGA, display port, ect.): via passive DVI-D -> HDMI cable
• Output device (video card, discrete graphics, ect.): Nvidia GTX 1050 Ti
• Operating system: Windows 10 (build 19045.3448)
• Python version: 3.11.6
• monitorcontrol version (monitorcontrol --version): 3.0.3

Steps to Reproduce

1. Start this snippet:

     import time
     
     from monitorcontrol import get_monitors
     
     if __name__ == '__main__':
         while True:
             for i, monitor in enumerate(get_monitors()):
                 with monitor:
                     print(f"Monitor #{i}: {monitor.get_power_mode()}")
                     time.sleep(3)

2. Wait until the display goes into standby, the issue should pop up after some time. It seems nondeterministic.
3. Here the self._get_vcp_feature(code) returns zero, then PowerMode(value) called with this 0 which raises {ValueError}0 is not a valid PowerMode

monitorcontrol/monitorcontrol/monitorcontrol.py

Lines 378 to 401 in a363456

	def get_power_mode(self) -> PowerMode:
	"""
	Get the monitor power mode.
	Returns:
	Value from the :py:class:`PowerMode` enumeration.
	Example:
	Basic Usage::
	from monitorcontrol import get_monitors
	for monitor in get_monitors():
	with monitor:
	print(monitor.get_power_mode())
	Raises:
	VCPError: Failed to get the power mode.
	ValueError: Set power state outside of valid range.
	KeyError: Set power mode string is invalid.
	"""
	code = vcp.VCPCode("display_power_mode")
	value = self._get_vcp_feature(code)
	return PowerMode(value)

Traceback (most recent call last):
  File "C:\Users\Username\AppData\Roaming\JetBrains\PyCharm2023.2\scratches\scratch_1.py", line 9, in <module>
    print(f"Monitor #{i}: {monitor.get_power_mode()}")
                           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\Projects\monitor\venv\Lib\site-packages\monitorcontrol\monitorcontrol.py", line 324, in get_power_mode
    return PowerMode(value)
           ^^^^^^^^^^^^^^^^
  File "C:\Users\Username\AppData\Local\Programs\Python\Python311\Lib\enum.py", line 712, in __call__
    return cls.__new__(cls, value)
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Username\AppData\Local\Programs\Python\Python311\Lib\enum.py", line 1135, in __new__
    raise ve_exc
ValueError: 0 is not a valid PowerMode

#288 Seems related.

[newAM]

Could also be related to #117.

Does this only occur in standby mode? There are a number of monitors that simply don't respond to DDC-CI commands in standby. It is strange that this is erratic though. Perhaps check if there are some monitor power features you can tweak?

[gabortim]

Yes, I've only seen it after the display entered standby. I'm going to profile it a bit more, maybe I'll find some patterns that help debug the case.

[gabortim]

When I wait for Windows to put the display in sleep, it's erratic.
When I explicitly set monitor.set_power_mode(PowerMode.off_soft), it instantly reproduces edit: still erratic :( I gave up on this.

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import time

from monitorcontrol import get_monitors, VCPError, PowerMode
from winsound import Beep

if __name__ == '__main__':
    monitor = get_monitors()[0]
    with monitor:
        monitor.set_power_mode(PowerMode.off_soft)

    while True:
        for i, monitor in enumerate(get_monitors()):
            with monitor:
                try:
                    print(f"Monitor #{i}: {monitor.get_power_mode()}")
                    time.sleep(3)
                except (VCPError, ValueError) as e:
                    while True:
                        Beep(450, 400)
                        time.sleep(0.1)

Also, I updated to monitorcontrol 3.1.0 and the trace changed a bit:

Traceback (most recent call last):
  File "D:\Projects\monitor\test\test_offline.py", line 18, in <module>
    print(f"Monitor #{i}: {monitor.get_power_mode()}")
                           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\Projects\monitor\venv\Lib\site-packages\monitorcontrol\monitorcontrol.py", line 390, in get_power_mode
    value = self._get_vcp_feature(code)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\Projects\monitor\venv\Lib\site-packages\monitorcontrol\monitorcontrol.py", line 184, in _get_vcp_feature
    current, maximum = self.vcp.get_vcp_feature(code.value)
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\Projects\monitor\venv\Lib\site-packages\monitorcontrol\vcp\vcp_windows.py", line 135, in get_vcp_feature
    raise VCPError("failed to get VCP feature: " + ctypes.FormatError())
monitorcontrol.vcp.vcp_abc.VCPError: failed to get VCP feature: A művelet meghiúsult, mert a DDC/CI-üzenet parancsmezője érvénytelen értéket tartalmazott.

Which resembles #288 (comment). I think I'm out of luck, but at least I know the issue is in my hardware.

[gabortim]

Changing closure state.