Pocketmine-mp: Slowness Effect levels >= 7 do not reset FOV when removed

[Muqsit]

Issue description

• Expected result: FOV reverts back to normal after slowness effect is removed/expires.
• Actual result: FOV does not revert back to normal until you rejoin. _This cannot be reproduced in vanilla_.

Steps to reproduce the issue

1. /give slowness 1 100
2. Your FOV wont revert back.

OS and versions

• PocketMine-MP: 48a7627
• PHP: 7.2RC6
• Server OS: Ubuntu 14.04 LTS 64-bit
• Game version: Win10

Plugins

• Test on a clean server without plugins: Issue still exists

[sylvrs]

I remember having this issue on earlier versions(dating back to 0.15). Running fixed it for me.

[dktapps]

The only way I can reproduce this is by using excessive amplifiers (>= 7) so that the player's speed decreases to zero. Is that what you're describing?

[Muqsit]

Yes. In vanilla, the speed does get put to zero when you use amplifier >= 7 but the FOV reverts back to normal once slowness goes away.

[dktapps]

The problem arises here: https://github.com/pmmp/PocketMine-MP/blob/master/src/pocketmine/entity/Effect.php#L474 - due to the dividend of the operation being zero. It's capped (is that the right word?) at zero when adding the effect and can't go below that.

In vanilla I think this is handled using attribute modifiers which effectively change the output value of an attribute, instead of modifying its base value directly. This is not implemented in PocketMine-MP.

Not sure how best to fix this - I don't think there's any real non-hacky way to do it.

[djdisodo]

https://github.com/pmmp/PocketMine-MP/blob/2d3ce9e8b027161c9d8b4145c94a3813d1ab9497/src/pocketmine/entity/Effect.php#L361
this sets negative value if effectlevel is >=7
how about
$attr->setValue(max($attr->getMinValue(),$attr->getValue() / (1 - 0.15 * $instance->getEffectLevel())));