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IgorTimofeev / MineOS

Home of MineOS and it's software for OpenComputers mod
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Question: In the Image API, every 603 pixels computer.pullSignal(0) is called. Why? #308

Closed CoolCat467 closed 3 years ago

CoolCat467 commented 3 years ago

I was looking at the Image API, and I noticed that in the local function "group" and in the module function "toString", every 603 pixels computer.pullSignal(0) is called. I was wondering why, because doing that would cause signals during that period to bypass being handled by the event API's handlers. I'm sure there's a reason for it, but I don't quite understand. Thank you for your time.

IgorTimofeev commented 3 years ago

Because of "too long without yielding" error. On low-end servers/clients computer will hang in grouping process of large pictures before saving/serializing them. Grouping is required for color palette optimization and reducing file/string size without any compression methods like deflate. On small pictures like OS icons computer.pullSignal will not be called.

Unlike OpenOS, MineOS does not replace the native computer.pullSignal function with a custom one in event.lua - therefore, you can safely call it any time, this will not trigger cascade execution of event handlers registered in the Event library. I deliberately avoid "function replace method" as I consider it "anti-pattern" that is hard to manage and potentially leading to the consequences that you have described (accidental execution of handlers when it's not needed). MineOS itself uses event.pull, not computer.pullSignal - so, we can assume that computer.pullSignal is just a low-level method, that was left untouched for such rare cases as "force sleeping for N secs for preventing TLWY errors" or something else

Btw I haven't encountered the need to turn off signal processing while doing anything... In which case do you have such a need? Or are you just wondering why this stuff needed?

CoolCat467 commented 3 years ago

I was just curious, because I couldn't tell why it was required just from the code. That makes perfect sense though! And I agree about the function overwriting thing. Thank you for explaining it.