AttributeError: _data / "gdi32.GetDIBits() failed" (Windows)

General information:

• OS name: Windows
• OS version: 10, version 1803
• OS architecture: 64-bit
• Resolutions:
  • Monitor 1: 1920x1080
  • Monitor 2: 1920x1080
• Python version: 3.6.5
• MSS version: 3.2.1

Description of the warning/error

MSS consistently throws the following error, always after my program has been running for a little over 3 hours, and after successfully capturing many (22,000+) screenshots in that time.

Full message

== 2018-07-15 07:17:17.953381 runtime: 3:09:39.428722 ==
('gdi32.GetDIBits() failed.', {'bits': 0, 'height': 665, 'width': 1033, 'gdi': <WinDLL 'gdi32', handle 7ffeff9b0000 at 0x1e9c1896898>, 'monitor': {'left': -1034, 'top': 31, 'width': 1033, 'height': 665}, 'self': <mss.windows.MSS object at 0x000001E9C1896860>})
Traceback (most recent call last):
  File "D:\IdeaProjects\Python\CaptureTest\main.py", line 98, in <module>
    run()
  File "D:\IdeaProjects\Python\CaptureTest\main.py", line 82, in run
    self.screenshot()
  File "D:\IdeaProjects\Python\CaptureTest\main.py", line 77, in screenshot
    self.im = self.window.screenshot()
  File "D:\IdeaProjects\Python\CaptureTest\main.py", line 84, in screenshot
    im = self.mss_instance.grab(area)
  File "C:\Users\Nick\AppData\Local\Programs\Python\Python36\lib\site-packages\mss\windows.py", line 202, in grab
    del self._data
AttributeError: _data

Other details

I’ve tried to replicate this error by simply calling mss.grab(...) in a while loop and seeing if it breaks after x number of screenshots, but that runs fine for at least 160,000 iterations, so I can’t figure out why my program consistently seems to break at ~3 hours runtime.

Upon viewing the MSS source, I realised that the del self._data line is directly followed by raise ScreenShotError('gdi32.GetDIBits() failed.', locals()), so I suppose my question is:

What could cause gdi32.GetDIBits() to spontaneously fail?

[BoboTiG]

I think I found the cause.

Redefine Window.exists() to free the allocated DC:

def exists(self):
    try:
        dc = win32gui.GetWindowDC(self.hwnd)
    except:
        return False
    else:
        win32gui.DeleteObject(dc)
        return True

Another benefit: this will be much faster.

[BoboTiG]

OK, long time since this issue was resolved, but i had time to check for a useful error message. This is was I found: GDI functions do not use LastError(), only return 0 on error.

I followed how ReactOS is doing and this is the revelant parts:

• GetDIBits() calls NtGdiGetDIBitsInternal;
• NtGdiGetDIBitsInternal() calls GreGetDIBitsInternal;
• and this is GreGetDIBitsInternal().

So, there is no way to get some error message …

Doing this investgation could open a new idea to improve speed on Windows: directly calls GreGetDIBitsInternal, if available.