Rust: Support delayed tasks in RunLoop

Rust: Support delayed tasks in RunLoop

Adds the ability to schedule a delayed task in the RunLoop.
The task is inserted as a closure and as long as one handle
lives in the RunLoop it is guaranteed to run at the confirmed
deadline (with no handlers the RunLoop exits).

R=eholk@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/fefa014de0c9b55547ea19ed005b252a00dbe2e2

[mknyszek, 2016-08-12 00:52:44]

mknyszek@google.com changed reviewers:
+ eholk@chromium.org, jamesr@chromium.org, phosek@google.com,
viettrungluu@chromium.org

[mknyszek, 2016-08-12 00:52:44]

Second-to-last CL, I'm leaving tomorrow and its small so if you could get this
in that would be great!

[Eric Holk, 2016-08-12 01:36:32]

lgtm otherwise

(admittedly, I looked over this pretty quickly)

https://codereview.chromium.org/2244463002/diff/40001/mojo/public/rust/src/bi...
File mojo/public/rust/src/bindings/run_loop.rs (right):

https://codereview.chromium.org/2244463002/diff/40001/mojo/public/rust/src/bi...
mojo/public/rust/src/bindings/run_loop.rs:145: closure: Box<Fn(&mut RunLoop) +
't>,
Can this be an FnOnce? A lot of times that gives you more flexibility it what
you can do in the closure.

https://codereview.chromium.org/2244463002/diff/40001/mojo/public/rust/src/bi...
mojo/public/rust/src/bindings/run_loop.rs:429: where F: Fn(&mut RunLoop) + 't
If you make the previous one an FnOnce, I think you'll have to do it here too.

[mknyszek, 2016-08-12 08:09:31]

https://codereview.chromium.org/2244463002/diff/40001/mojo/public/rust/src/bi...
File mojo/public/rust/src/bindings/run_loop.rs (right):

https://codereview.chromium.org/2244463002/diff/40001/mojo/public/rust/src/bi...
mojo/public/rust/src/bindings/run_loop.rs:145: closure: Box<Fn(&mut RunLoop) +
't>,
On 2016/08/12 01:36:31, Eric Holk wrote:
> Can this be an FnOnce? A lot of times that gives you more flexibility it what
> you can do in the closure.

That's true, but unfortunately Rust doesn't support calling a Box<FnOnce> at all
since FnOnce needs to consume itself, but being a trait it is not SIzed. There
is a workaround called FnBox which is an extension of FnOnce meant to be called
from inside a Box, but its currently sitting in nightly as an unstable feature.
In the future Rust plans to fix this by having Box<FnOnce> just work (maybe by
implementing some specialization for the precise type Box<FnOnce>?), but for now
it just doesn't.

As a short-term fix I have still loosened the trait bound on the closure to
FnMut, which should make it a little bit easier to use. Realistically, FnOnce is
all I need, but its not yet available in the context I want to use it in (that
is, from inside a Box).

[Eric Holk, 2016-08-12 16:35:08]

https://codereview.chromium.org/2244463002/diff/40001/mojo/public/rust/src/bi...
File mojo/public/rust/src/bindings/run_loop.rs (right):

https://codereview.chromium.org/2244463002/diff/40001/mojo/public/rust/src/bi...
mojo/public/rust/src/bindings/run_loop.rs:145: closure: Box<Fn(&mut RunLoop) +
't>,
On 2016/08/12 08:09:31, mknyszek wrote:
> On 2016/08/12 01:36:31, Eric Holk wrote:
> > Can this be an FnOnce? A lot of times that gives you more flexibility it
what
> > you can do in the closure.
> 
> That's true, but unfortunately Rust doesn't support calling a Box<FnOnce> at
all
> since FnOnce needs to consume itself, but being a trait it is not SIzed. There
> is a workaround called FnBox which is an extension of FnOnce meant to be
called
> from inside a Box, but its currently sitting in nightly as an unstable
feature.
> In the future Rust plans to fix this by having Box<FnOnce> just work (maybe by
> implementing some specialization for the precise type Box<FnOnce>?), but for
now
> it just doesn't.
> 
> As a short-term fix I have still loosened the trait bound on the closure to
> FnMut, which should make it a little bit easier to use. Realistically, FnOnce
is
> all I need, but its not yet available in the context I want to use it in (that
> is, from inside a Box).

Sounds good!

[mknyszek, 2016-08-12 17:22:49]

Description was changed from

==========
Rust: Support delayed tasks in RunLoop
==========

to

==========
Rust: Support delayed tasks in RunLoop

Adds the ability to schedule a delayed task in the RunLoop.
The task is inserted as a closure and as long as one handle
lives in the RunLoop it is guaranteed to run at the confirmed
deadline (with no handlers the RunLoop exits).
==========

[mknyszek, 2016-08-12 17:23:22]

Description was changed from

==========
Rust: Support delayed tasks in RunLoop

Adds the ability to schedule a delayed task in the RunLoop.
The task is inserted as a closure and as long as one handle
lives in the RunLoop it is guaranteed to run at the confirmed
deadline (with no handlers the RunLoop exits).
==========

to

==========
Rust: Support delayed tasks in RunLoop

Adds the ability to schedule a delayed task in the RunLoop.
The task is inserted as a closure and as long as one handle
lives in the RunLoop it is guaranteed to run at the confirmed
deadline (with no handlers the RunLoop exits).

R=eholk@chromium.org

Committed:
https://chromium.googlesource.com/external/mojo/+/fefa014de0c9b55547ea19ed005...
==========

[mknyszek, 2016-08-12 17:23:23]

Committed patchset #4 (id:60001) manually as
fefa014de0c9b55547ea19ed005b252a00dbe2e2 (presubmit successful).