on_press gives different key attributes values when backend is uinput

[bjr-lopos]

Hi all,

the "key" object given by the on_press event on a xorg backend is different compared to an uinput backend. The xorg backend was used as development environment on Ubuntu 20.04.1 LTS. The uinput backend on this environment which we are focusing on:

• hardware: raspberry pi 3b v2, keyboard and bar-code scanner only
• OS: Raspberry Pi OS (32-bit) Lite 2020-08-20.
• version pynput 1.7.1

We ran this minimal python script on both environments.

def on_press(key):
    pprint(vars(key))

listener = Listener( on_press=on_press)
listener.start()

while True:
  time.sleep(1)

For the keys (enter, 'a' and numpad 2) on a xorg backend (as non-root on Ubuntu) we get:

{'__objclass__': <enum 'Key'>, '_name_': 'enter', '_value_': <65293>}
{'_symbol': None, 'char': 'a', 'combining': None, 'is_dead': False, 'vk': 97}
{'_symbol': None, 'char': '2', 'combining': None, 'is_dead': False, 'vk': None}

For the same keys on a uinput backend (as root on the pi) env we get:

{'_kernel_name': None, '_x_name': None, 'char': 'Key.enter', 'combining': None, 'is_dead': False, 'vk': 28}
{'_kernel_name': None, '_x_name': None, 'char': "'a'", 'combining': None, 'is_dead': False, 'vk': 16}
{'_kernel_name': None, '_x_name': None, 'char': None, 'combining': None, 'is_dead': False, 'vk': 80}

showkey shows similiar output on both systems. In a bash terminal the keyboard behaves normal. We would like to handle the keys in Python in an uniform way. Are we missing a mapping in the OS or in python?

Thanks,

Bart

[moses-palmer]

Thank you for your report.

The only attribute of a key that can be relied upon to be portable between different backends is char. When looking at your example output, it is clear that that is not the case; the values for the uinput backend are incorrect. I will look into this.

[moses-palmer]

I have prepared a small for for the uinput backend in fixup-uinput-keycodes. It seems to work properly now, but I would very much appreciate if you could test it also.

[moses-palmer]

I close this issue due to lack of feedback with the assumption that the branch mentioned above, which has now been merged into the main branch, solves it.

If it does not, please reopen this issue.