Opposing direction combination inputs cause glitched movements

[ghost]

Description

When pressing / quickly alternating / holding both left and right (or up and down in some games) directions at the same time, unusual behavior that can best be described as zipping occurs, and can cause the player to clip through ground / walls / etc. Needless to say, it's banned in the speedrunning community and should be disabled by default as Core Option / Input Setting.

Standalone emulators like FCEUX have an option disabled by default labeled Allow Up+Down / Left+Right. I feel it'd be best if RetroArch adopted this.

I'm going to tag @fr500 just in case he's interested due to all of his hard work on the new input mapper.

Expected behavior

Pressing left and right / up and down simultaneous is not physically possible except on a keyboard (unless the d-pad has been remapped to buttons) and shouldn't be allowed, at least by default. Standalone emulators like FCEUX have an option disabled by default labeled Allow Up+Down / Left+Right. I feel it'd be best if RetroArch adopted this.

Actual behavior

See video: https://streamable.com/9n6sz

See also:

Steps to reproduce the bug

1. Load a sidescrolling action / platform game such as Zelda II - The Adventure of Link (NES) or Bonk's Adventure (GB)
2. Press and hold (or even quickly alternate / hold one and tap the other) left and right (on a keyboard unless you remapped d-pad left and d-pad right to actual buttons)
3. Observe

Bisect Results

Did not bisect.

Version/Commit

• RetroArch: 1.7.2 24b694d

Environment information

• OS: Debian 9 (Stretch) Stable x86_64
• Compiler: gcc 3.6.0 64-bit

[inactive123]

OK, just to be clear, this issue always happened and is not necessarily related to the new input remapping code right?

[ghost]

I'd like to say so given it affects even standalone emulators, I believe this is a Day 1 issue that's been simply overlooked. However, the remapping code allows for it occur via controller if one remaps the d-pad to buttons and then holds at least one while tapping or holding another.

[inactive123]

Added core options to FCEUmm, snes9x git and Gambatte for this.

[ghost]

Can confirm options work for mentioned cores. Should I close this or leave it open in case I find other affected cores?

[i30817]

Does this matter for the snes? I've seen it nes (in Zelda II too) but not on snes games? I guess it doesn't really matter though. since opposing directions is something that no game wants you to press.

[i30817]

BTW, can you please test 'Die Hard (Japan).pce' in mednafen_pce_fast_libretro? If you move the movement keys here for a while tapping, you'll eventually get into a infinite cycle of spinning. Not sure if the same problem? It's easy to see just by starting the game level 1 (it starts automatically) and then messing around with the keys.

[ghost]

I'll look into it after I catch up with the other stuff I need to do first. Hopefully some time today.

[inactive123]

OK, open new issues up in the individual core repos that need a fix.

[ghost]

Will do. Thanks

[ghost]

@i30817 Can confirm, will file an issue later. It seems to require that at least 3 different directions need to be pressed at once to trigger the infinite spinning glitch. New Adventure Island does some.... interesting things when Up+Down is held.