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Another question for the similar topic. I need to use custom clock to count delays (virtual clock to be specific). Do I need to implement my own event loop to be able to "wake" on specific event?

You certainly need a `while (true)` at some point, because no one but you knows whether there are tasks left for your custom dispatcher to process. You can abstract the lower-level details away, though, by reusing the event loop from `runBlocking`. We do that in `kotlinx-coroutines-test` (<https://github.com/Kotlin/kotlinx.coroutines/blob/465e29d325841244f3a1aac2e13073bc965f9736/kotlinx-coroutines-test/common/src/TestBuilders.kt#L324-L361|https://github.com/Kotlin/kotlinx.coroutines/blob/465e29d325841244f3a1aac2e13073bc965f9736/kotlinx-coroutines-test/common/src/TestBuilders.kt#L[…]61>), though I suspect we'll change that eventually.

The primary question is how can I notify scheduler that delay is ended

I'm not sure that I understand the question, but probably something like this <https://github.com/Kotlin/kotlinx.coroutines/issues/2024> ?

I will check. What I mean is that I set `delay` , say for 200 milliseconds, then I need for it to record time mark in virtual time scheduler and if all other timelines are right it should immediately continue without waiting for real 200 milliseconds. I mean that I need to notify scheduler that time has passed.

Or I want to hold delay for longer time until virtual time is right

In general, I need to manually trigger the end of delay

Looks fairly similar to what we do in `kotlinx-coroutines-test`, except that we never wait for any real time. I think <https://github.com/Kotlin/kotlinx.coroutines/blob/465e29d325841244f3a1aac2e13073bc965f9736/kotlinx-coroutines-test/common/src/TestBuilders.kt#L324-L336|https://github.com/Kotlin/kotlinx.coroutines/blob/465e29d325841244f3a1aac2e13073bc965f9736/kotlinx-coroutines-test/common/src/TestBuilders.kt#L[…]36> together with <https://github.com/Kotlin/kotlinx.coroutines/blob/465e29d325841244f3a1aac2e13073bc965f9736/kotlinx-coroutines-test/common/src/TestDispatcher.kt> and <https://github.com/Kotlin/kotlinx.coroutines/blob/465e29d325841244f3a1aac2e13073bc965f9736/kotlinx-coroutines-test/common/src/TestCoroutineScheduler.kt|https://github.com/Kotlin/kotlinx.coroutines/blob/465e29d325841244f3a1aac2e13073bc[…]36/kotlinx-coroutines-test/common/src/TestCoroutineScheduler.kt> should give the full picture.

Exactly that I am studying right now. I just thought that maybe there is a simpler way to give the scheduler wake up call

This heavily depends on how you implement the process of sleeping. If it's `LockSupport.parkNanos`, call `unpark`. If it's `kotlinx.coroutines.delay`, replace that with `select { }` with the timeout clause and the clause for obtaining the "time to wake up" message channel. If it's `Thread.sleep`, your friend is `Thread.interrupt`.