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#coroutines
Title
# coroutines
d

Dico

03/09/2019, 1:09 PM
Sometimes I find a need for 
withScope
instead of 
withContext
. Now you have to write 
withContext(myScope.coroutineContext)
but, given the intended purpose 😉 of 
CoroutineScope
, I feel there should be a scope variant of it.
d

Dias

03/09/2019, 1:34 PM
is it not what coroutineScope {} does?
d

Dico

03/09/2019, 1:43 PM
You cant pass an explicit scope to that
I feel one potential issue which is that you cant really have 2 parents, when ideally, 
withScope
can give you 2 parents. I assume 
withContext
makes the paraneter's Job take precedence. Just entertaining some thoughts.
e

elizarov

03/09/2019, 2:21 PM
What would be your use-case for two parents?
d

Dico

03/09/2019, 2:31 PM
That's a good question. I think the reason is that you have to drop one relationship when you want to change to another 
CoroutineScope
. Maybe that's how it should be, and maybe that's why it's good that 
withScope
doesn't exist.
e

elizarov

03/09/2019, 2:32 PM
But what is the use-case? Where it comes up?
d

Dico

03/09/2019, 2:36 PM
I have an application where I'm rendering using OpenGL. The application is slowed down significantly by a particular aspect of it because it can make around 2 million queries to the memory of a particular process per frame. Hitting 20ms of frame time is not ideal. All of that work could be done on another thread, as it's just creating vertices in a buffer. That job should ideally be dependent on both scopes being alive; the main scope and the one I want to add.
e

elizarov

03/09/2019, 2:37 PM
What’s your main scope and which one you want to add?
d

Dico

03/09/2019, 2:38 PM
My main scope is the one with the opengl context, it wraps an event loop. The new one would be on the default dispatcher.
I think a good solution to that would be to cancel the new scope when the main scope dies
Anyway, I'm just giving the idea of multiple parents a thought, I'm not necessarily advocating for it. I think it would bring many problems with it that would ultimately make it a bad idea.
What I end up doing each loop in the second thread, at the end is this:
Copy code
MainScope.launch {
    vertexBuffer.sync() // upload to GPU
}.join() // ensure it's uploaded before next iteration
This is OK. But 
withContext
like mechanism would be more elegant. That's all.
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