ctypes: прохождение и чтение указателя перечислимой

Question

This page говорит:

типы перечисления не реализованы. Вы можете легко сделать это, используя c_int в качестве базового класса.

Если бы это было легко, почему это еще не реализовано? Как, например, get the current color temperature of my monitor?

BOOL GetMonitorColorTemperature(
    _In_ HANDLE hMonitor, 
    _Out_ LPMC_COLOR_TEMPERATURE pctCurrentColorTemperature 
); 

Parameters 

hMonitor [in] 

    Handle to a physical monitor. To get the monitor handle, call GetPhysicalMonitorsFromHMONITOR or GetPhysicalMonitorsFromIDirect3DDevice9. 
pctCurrentColorTemperature [out] 

    Receives the monitor's current color temperature, specified as a member of the MC_COLOR_TEMPERATURE enumeration. 

Return value 

If the function succeeds, the return value is TRUE. If the function fails, the return value is FALSE. To get extended error information, call GetLastError. 

Это ближайший я смог:

from ctypes import * 

import win32api # http://sourceforge.net/projects/pywin32/files/pywin32/ 

for idx, (hMon, hDC, (left, top, right, bottom)) in enumerate(win32api.EnumDisplayMonitors(None, None)): 
    print(hMon.handle) # or int(hMon) 

class MyEnum(c_int): 
    MC_COLOR_TEMPERATURE_UNKNOWN = 0 
    MC_COLOR_TEMPERATURE_4000K = 1 
    MC_COLOR_TEMPERATURE_5000K = 2 
    MC_COLOR_TEMPERATURE_6500K = 3 
    MC_COLOR_TEMPERATURE_7500K = 4 
    MC_COLOR_TEMPERATURE_8200K = 5 
    MC_COLOR_TEMPERATURE_9300K = 6 
    MC_COLOR_TEMPERATURE_10000K = 7 
    MC_COLOR_TEMPERATURE_11500K = 8 

o = MyEnum() 
print(o) 
po = pointer(o) 
t = windll.dxva2.GetMonitorColorTemperature(hMon.handle, po) #byref(o)) 
#print(dir(o)) 
print(o) 
print(po.contents) 
print(t) 
print(windll.kernel32.GetLastError()) # ERROR_GRAPHICS_INVALID_PHYSICAL_MONITOR_HANDLE = -1071241844 # Variable c_long '-0x03fd9da74' 

... возвращает это:

65537 
65539 
<MyEnum object at 0x006F6DA0> 
<MyEnum object at 0x006F6DA0> 
<MyEnum object at 0x0234FAD0> 
0 
-1071241844 

Это то же самое для любого монитора ручки. Что я делаю не так?

Answer 1

Используя this answer, я как-то узнал, что это работает, используя None в качестве физической ручки монитора:

from ctypes import * 
from ctypes.wintypes import BOOL, HMONITOR, HDC, RECT, LPARAM, DWORD, BYTE, WCHAR, HANDLE 

import win32api # http://sourceforge.net/projects/pywin32/files/pywin32/ 

_MONITORENUMPROC = WINFUNCTYPE(BOOL, HMONITOR, HDC, POINTER(RECT), LPARAM) 

class _PHYSICAL_MONITOR(Structure): 
    _fields_ = [('handle', HANDLE), 
       ('description', WCHAR * 128)] 


def _iter_physical_monitors(close_handles=True): 
    """Iterates physical monitors. 

    The handles are closed automatically whenever the iterator is advanced. 
    This means that the iterator should always be fully exhausted! 

    If you want to keep handles e.g. because you need to store all of them and 
    use them later, set `close_handles` to False and close them manually.""" 

    def callback(hmonitor, hdc, lprect, lparam): 
     monitors.append(hmonitor) 
     return True 

    monitors = [] 
    if not windll.user32.EnumDisplayMonitors(None, None, _MONITORENUMPROC(callback), None): 
     raise WinError('EnumDisplayMonitors failed') 

    for monitor in monitors: 
     # Get physical monitor count 
     count = DWORD() 
     if not windll.dxva2.GetNumberOfPhysicalMonitorsFromHMONITOR(monitor, byref(count)): 
      raise WinError() 
     # Get physical monitor handles 
     physical_array = (_PHYSICAL_MONITOR * count.value)() 
     if not windll.dxva2.GetPhysicalMonitorsFromHMONITOR(monitor, count.value, physical_array): 
      raise WinError() 
     for physical in physical_array: 
      yield physical.handle 
      if close_handles: 
       if not windll.dxva2.DestroyPhysicalMonitor(physical.handle): 
        raise WinError() 

mons = [m for m in _iter_physical_monitors(False)] 

#for idx, (hMon, hDC, (left, top, right, bottom)) in enumerate(win32api.EnumDisplayMonitors(None, None)): 
# print(hMon.handle) # or int(hMon) 

temps = (
    'UNKNOWN', 
    '4000K', 
    '5000K', 
    '6500K', 
    '7500K', 
    '8200K', 
    '9300K', 
    '10000K', 
    '11500K' 
) 
class MyEnum(c_int): 
    MC_COLOR_TEMPERATURE_UNKNOWN = 0 
    MC_COLOR_TEMPERATURE_4000K = 1 
    MC_COLOR_TEMPERATURE_5000K = 2 
    MC_COLOR_TEMPERATURE_6500K = 3 
    MC_COLOR_TEMPERATURE_7500K = 4 
    MC_COLOR_TEMPERATURE_8200K = 5 
    MC_COLOR_TEMPERATURE_9300K = 6 
    MC_COLOR_TEMPERATURE_10000K = 7 
    MC_COLOR_TEMPERATURE_11500K = 8 

o = MyEnum() 
print(o) 
po = pointer(o) 

pm = mons[0] 
print("physical %r" % pm) 
t = windll.dxva2.GetMonitorColorTemperature(pm, po) #byref(o)) 
if t: 
    #print(o) 
    #print(dir(po.contents)) 
    print(temps[po.contents.value]) 

else: 
    print("Err: %s" % windll.kernel32.GetLastError()) # ERROR_GRAPHICS_INVALID_PHYSICAL_MONITOR_HANDLE = -1071241844 # Variable c_long '-0x03fd9da74' 

Результат:

<MyEnum object at 0x005D6120> 
physical None 
6500K