General information:

• OS name: Ubuntu
• OS version: 20.04
• OS architecture: 64 bits
• Resolutions:
  • Monitor 1: 1920x1080
• Python version: 3.8.2
• MSS version: 5.0.0

For GNU/Linux users:

• Display server protocol and version, if known: Wayland
• Desktop Environment: Gnome
• Composite Window Manager name and version: Unknown

Description of the warning/error

When running mss under Wayland, it crashs. As far as I understand from the source code, mss currently uses xlib for Linux, which seems to (unsurprisingly) not work on Wayland. It would be very cool to have wayland support implemented, as it becomes more and more popular.

Full message

Example: Executing the following snippet under X works perfectly, while under Wayland it produces an error.

Snippet:

import mss
fn = mss.mss().shot(mon=-1, output="screenshot.png")
print(fn)

Error on Wayland:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/holger/.local/lib/python3.8/site-packages/mss/factory.py", line 41, in mss
    return linux.MSS(**kwargs)
  File "/home/holger/.local/lib/python3.8/site-packages/mss/linux.py", line 226, in __init__
    self.root = self.xlib.XDefaultRootWindow(MSS.display)
  File "/home/holger/.local/lib/python3.8/site-packages/mss/linux.py", line 175, in validate
    raise ScreenShotError(err, details=details)
mss.exception.ScreenShotError: XDefaultRootWindow() failed

Other details

A lot of screenshot tools (e.g. shutter) have this issue, because screenshots seem to work completely different in Wayland (to improve security). Applications that do work are e.g.:

• gnome-screenshot, which is e.g. leveraged by the python-lib pyscreenshot
• flameshot works too, but seems not to have implemented the "proper" way here (see below).

A proper way to do screenshots under Wayland is referenced in a flameshot issue and might help solving this in mss, too. The main statement from that issue:

The cross-platform way to take screenshots on Wayland is via xdg-desktop-portal (which also works outside of Flatpak). See https://github.com/flatpak/xdg-desktop-portal/blob/master/data/org.freedesktop.portal.Screenshot.xml