ThreadSafety: gdi32.GetDIBits() failed

[anawkward]

General information:

• OS name: windows7
• OS version: sid
• OS architecture: 64 bits
• Resolutions:
  • Monitor 1: 1900x1200
  • Monitor 2: 1900x1200
• Python version: 3.7.3
• MSS version: 6.1.0

Description of the warning/error

import threading
import mss
import time

region1 = (0,0,1900,1200)
region2 = (0,0,100,100)

# A) make a grabbing thread

class a_thread(threading.Thread):
    def run(self):
        sct = mss.mss()
        while True:
            sct.grab(region1)
            time.sleep(1)


t = a_thread()
t.start()

time.sleep(1)

# B) grab

sct = mss.mss()
x = sct.grab(monitor=region2)

# the codes above gives an {ScreenShotError("gdi32.GetDIBits() failed.")} Exception.

Full message

Exception in thread Thread-8:
Traceback (most recent call last):
File "C:\Anaconda3\lib\threading.py", line 917, in _bootstrap_inner
self.run()
File "", line 12, in run
File "C:\Anaconda3\lib\site-packages\mss\base.py", line 88, in grab
return self._grab_impl(monitor)
File "C:\Anaconda3\lib\site-packages\mss\windows.py", line 285, in _grab_impl
raise ScreenShotError("gdi32.GetDIBits() failed.")
mss.exception.ScreenShotError: gdi32.GetDIBits() failed.

Other details

I think the error is related with the thread safety of mss.mss(). I did some A/B tests to reproduce it.

1. when region1 = region2, it was okay. error didn't appear.
2. when (B) is done before (A), like (B) -> (A) -> (B), it was okay. no error appeared.

I guess the cause is somewhere around the initialization of mss.mss() and a grab() method does something on the initialization.
I hope this issue helps to improve thread safety. contact me for any further information if needed.

[BoboTiG]

@anawkward would you be able to retry with changes from #211?

[FlorinPT]

@anawkward can you help me

[CTPaHHuK-HEbA]

@FlorinPT Check closed issue #212