Deep dive on input processing with Python

[hyshka]

We need to investigate some options for handling keyboard input on a lower level than asciimatics provides us with. This will let us bypass OS-level keyboard settings and give us the ability to handle both key up and key down events.

[hyshka]

Input handling libraries

• https://github.com/boppreh/keyboard, requires root on linux but does not depend on X11
• https://github.com/moses-palmer/pynput, may require root on mac osx and additional permissions, requires X11 on linux
• https://github.com/marcusva/py-sdl2, low level, cross platform, seems to require initializing a graphical window in order to listen to events
• https://liballeg.org/bindings.html, python bindings for C lib, low level, cross platform, similar to SDL2

Frameworks

• https://github.com/reidrac/pysdl2-harness, provides utilities to manage game and event loops using pysdl2
• https://github.com/libtcod/python-tcod, python port of popular roguelike framework, uses SDL2 for event handling, no terminal rendering?
• https://github.com/pygame/pygame, the beast itself, no terminal rendering, did it support key up events? Maybe uses SDL1 for event handling?
• https://github.com/arnauddupuis/pygamelib, terminal-based framework

Tutorials

• http://rogueliketutorials.com/tutorials/tcod/v2/, python-tcod tutorial
• http://inventwithpython.com/pygame/, free pygame book

Examples

• https://github.com/rswinkle/inventwithpython_pysdl2, small pysdl2 games
• https://github.com/LukeMS/pysdl2-roguelike-tutorial
• https://github.com/tomdaley92/py-pong, pysdl2
• https://github.com/shenjinti/pysdl2-flappybird, pysdl2

[hyshka]

• pygamelib
  • looks really interesting
  • does not seem to handle key down/up events
  • looks very tailored to a board/player/npc roguelike game
• python-tcod
  • cross-platform
  • opens a new window, not directly in terminal (like pygame)
  • terminal-like rendering though since it's geared towards classic roguelikes
  • key down and key up events work
• pysdl2-harness
  • cross-platform not tested
  • all rendering happens in a new window
  • key up and key down not tested

[amorriscode]

I'll admit, I haven't had much time to dig into this but this looks useful: https://stackoverflow.com/questions/27215326/tkinter-keypress-keyrelease-events

[hyshka]

^^^ appears as though tkinter also relies on opening a second window, similar to pygame, python-tcod, etc.

Really cool that this is built into python though!

[amorriscode]

Oh, whoops. I never had a chance to run it but wasn't clear that was the case. My bad. 😳

[hyshka]

Asciimatics input handling

• reads key-press events only
• cannot understand key-up or when keys are held down
• can block execution to wait for an event, or check events with each step of the event loop
• events can be processed via the Scene (GameController) and also in Effects

Notable side effects

• when keys are held down, the key events are repeated, but after an unknown delay which is determined by the OS
  • it's possible this could be adjusted on an OS-specific level, but the user would be required to do this manually
  • archlinux example, should work for most X11 users: https://wiki.archlinux.org/index.php/Xorg/Keyboard_configuration#Adjusting_typematic_delay_and_rate
  • xset r rate 100 60 for 100 ms delay and 60 Hz, typing was still OK at this setting but not ideal
  • with this setting, there is still a small flicker but only occaisionally
  • a 75 90 setting, I noticed flicker less but still sometimes, and this makes it very difficult to type normally
  • how this can be accomplished in other OS' is unknown

Functional workarounds

• remove the notion of "plucking a string" so that a key press creates both a fret press and string pluck
  • we would not be able to support notes held for a duration and may need to adjust the UI for this
• we require the user to configure their key repeat delay and perhaps implement an optimal amount of debouncing in-game
  • these key settings would have to be applied before the game, and unapplied after the game
  • debouncing might be tricky to get right
  • we have a hacky "key-hold" process, if the key event is not coming in, it is reset to off

[amorriscode]

Excellent research!

I think we should just do the first workaround. No one should expect this to be a replacement for Guitar Hero (at least for v1). If they really want a perfect clone with a keyboard, they can play Frets on Fire. :)

[hyshka]

Okay, that sounds good to me and prevents the need to workaround OS-level stuff manually.