I have a Windows message loop. I need to detect when the screen powers back up. Is there a windows message?
detect power state change contains the C# way, I need the C++ way, using win32 API.
If there isn't a Windows message, how do I poll for screen monitor power state?
There is a Windows message WM_POWERBROADCAST. There Windows API has a lot of support for power management. See the section on Windows Power Management at MSDN for the details.
For newer windows versions (starting with windows 8) you should use GUID_CONSOLE_DISPLAY_STATE instead of GUID_MONITOR_POWER_ON