bug with arrow keys in input system ?

[anthonov]

I get a weird behavior with arrow keys input :

When i hold ↑ and → and then i hold ←, the Input.GetKey(keycode.left) will not be register.
Even if i release ↑ and → , and i keep ← hold, it will still not be register as a holding key.
Same if i inverse the process with left and right.

Can someone confirm im not alone ?
Unity 2019.2.11f

[Madgvox]

Sounds like you have a keyboard with 2-key rollover.

[anthonov]

@Madgvox

Sounds like you have a keyboard with 2-key rollover.

ok but i can do ctrl-alt-sup that’s 3 keys so ?..
[edit]
I did a test at this link http://en.key-test.ru/
result is inconsistency on my keyboard…
if i hold up and down, then left will not work, but right yes …

[Madgvox]

@inputchaos

ok but i can do ctrl-alt-sup that’s 3 keys so ?..
[edit]
I did a test at this link http://en.key-test.ru/
result is inconsistency on my keyboard…
if i hold up and down, then left will not work, but right yes …

That kind of behaviour is explained in the wikipedia article (emphasis mine):

[…] there are many cases when more than two keys need to be depressed at the same time, such as Ctrl-Alt-Delete, or when more than two keys are depressed because of fast typing (“rolling over” more than two keys). […] the most common key sequences have been studied, and keys in the same common sequence are placed in the electrical switch matrix such that three keys down cannot produce a fourth “phantom” key by shorting out the matrix. […] This typically produces four- to five-key rollover for the most common key sequences.

In short, you can do ctrl+alt+sup because the keyboard is designed to support those sequences without shorting out the matrix. However, in keyboards that aren’t designed for gaming, it’s possible that they placed less emphasis on underutilized keys such as the arrow keys when designing the circuitry. This would explain the inconsistent behaviour you’re seeing.

In any case, this has nothing to do with Unity, and everything to do with the hardware you’re using. It’s possible that you can get better results by using WASD (for example), which could be more forgiving with higher key rollover.

[anthonov]

@Madgvox

That kind of behaviour is explained in the wikipedia article (emphasis mine):

In short, you can do ctrl+alt+sup because the keyboard is designed to support those sequences without shorting out the matrix. However, in keyboards that aren’t designed for gaming, it’s possible that they placed less emphasis on underutilized keys such as the arrow keys when designing the circuitry. This would explain the inconsistent behaviour you’re seeing.

In any case, this has nothing to do with Unity, and everything to do with the hardware you’re using. It’s possible that you can get better results by using WASD (for example), which could be more forgiving with higher key rollover.

thanks for the explanation