Poll Wacom input from "libinput debug-events" in Bash Post: 303039686

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Top Forums Shell Programming and Scripting Poll Wacom input from "libinput debug-events" in Bash Post 303039686 by mrjpaxton on Saturday 12th of October 2019 12:43:42 AM

10-12-2019

Registered User

Poll Wacom input from "libinput debug-events" in Bash

Hey,

I am making a Bash shell script to grab input from libinput. There's a few reasons why I am doing it this way:

Using Python with python-libinput does not work. I installed version 0.1.0 with pip, and it complains about "ContextType" not existing. So that's a no-go.
I am trying to get away from my dependence on Xorg-related stuff, such as xsetwacom and xserver-input-wacom, and do things that are more compatible with Wayland.
Both methods above do not have support for the four different modes when you press the center ring button on the ExpressKey pad. I plan to eventually support all of these events.

Without explaining my entire plan of this script, I figured I could ask the question that's harder for me to understand, and figure out the rest as I go along.

I want to poll the outputs from "libinput debug-events" in an infinite loop Bash script that will run in the background. This polling will happen, say, every 1 second.

This pseudocode down below can help explain what I am looking to do to start out my script:

Code:

#!/bin/bash
  
while true; do
  sleep 1
  OUTPUT=$(libinput debug-events | grep "TABLET_PAD_BUTTON")
  case ${OUTPUT} in
  "4 pressed (mode 0)")
    echo "Button 4"
    ;;
    # Etc . . .
  esac
done

My big problem is figuring out how to do this.

The thing is, "libinput debug-devices" works a lot like showkey or xev, but not exactly. For some reason, stdin for "TABLET_PAD_BUTTON" is "frozen" until I move the mouse around. Why this is, I have no idea. Regardless to say, I feel like I may be overcomplicating my problem, or I just don't really see a clear cut solution. Doing it this way just doesn't work right, as it is.

The libinput binary program will need to somehow exit after a period of time, because by default it is left running, so some sort of control implementation needs to exist there. Also, I notice that when it loops back to "OUTPUT=xyz" the existing variable data should be replaced by new input data again, which is great. That's exactly how it should work in that case.

Finally, this is a script that needs to run in the background (like a daemon process), and also accept input from libinput/udev devices at all times. And I'm not sure if Bash is powerful enough to tell the libinput binary to do that, is the thing.... If this really needs to be written in C, then perhaps there's no good solution here, and the thread can be closed if that's the case.

Anybody have any idea how I could approach this problem, or could even possibly provide a good bash script solution? Thank you very much in advance!

Last edited by mrjpaxton; 10-12-2019 at 01:55 AM..

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idle

IDLE(1) 						      General Commands Manual							   IDLE(1)

NAME

       IDLE - An Integrated DeveLopment Environment for Python

SYNTAX

       idle [ -dins ] [ -t title ] [ file ...]

       idle [ -dins ] [ -t title ] ( -c cmd | -r file ) [ arg ...]

       idle [ -dins ] [ -t title ] - [ arg ...]

DESCRIPTION

       This  manual page documents briefly the idle command.  This manual page was written for Debian because the original program does not have a
       manual page.  For more information, refer to IDLE's help menu.

       IDLE is an Integrated DeveLopment Environment for Python. IDLE is based on Tkinter, Python's bindings to the Tk widget  set.  Features  are
       100%  pure  Python, multi-windows with multiple undo and Python colorizing, a Python shell window subclass, a debugger. IDLE is cross-plat-
       form, i.e. it works on all platforms where Tk is installed.

OPTIONS

       -h     Print this help message and exit.

       -n     Run IDLE without a subprocess (see Help/IDLE Help for details).

       The following options will override the IDLE 'settings' configuration:

       -e     Open an edit window.

       -i     Open a shell window.

       The following options imply -i and will open a shell:

       -c cmd Run the command in a shell, or

       -r file
	      Run script from file.

       -d     Enable the debugger.

       -s     Run $IDLESTARTUP or $PYTHONSTARTUP before anything else.

       -t title
	      Set title of shell window.

       A default edit window will be bypassed when -c, -r, or - are used.

       [arg]* and [file]* are passed to the command (-c) or script (-r) in sys.argv[1:].

EXAMPLES

       idle   Open an edit window or shell depending on IDLE's configuration.

       idle foo.py foobar.py
	      Edit the files, also open a shell if configured to start with shell.

       idle -est "Baz" foo.py
	      Run $IDLESTARTUP or $PYTHONSTARTUP, edit foo.py, and open a shell window with the title "Baz".

       idle -c "import sys; print sys.argv" "foo"
	      Open a shell window and run the command, passing "-c" in sys.argv[0] and "foo" in sys.argv[1].

       idle -d -s -r foo.py "Hello World"
	      Open a shell window, run a startup script, enable the debugger, and run foo.py, passing "foo.py" in sys.argv[0] and "Hello World" in
	      sys.argv[1].

       echo "import sys; print sys.argv" | idle - "foobar"
	      Open a shell window, run the script piped in, passing '' in sys.argv[0] and "foobar" in sys.argv[1].

SEE ALSO

       python(1).

AUTHORS

       Various.

								 21 September 2004							   IDLE(1)