1675118 - Add a variant of AsyncInvoker that supports posting completion runnables

Status: RESOLVED FIXED

(Core :: IPC: MSCOM, enhancement)

Description

[(No longer employed by Mozilla) Aaron Klotz]

This is to allow us to receive completion events from async COM interfaces without needing to block on anything.

Comment 1

[(No longer employed by Mozilla) Aaron Klotz]

Attachment: Bug 1675118: Add a variant of mscom::AsyncInvoker that supports posting completion runnables; r=Jamie

I need this for some changes I want to make to Win32 file pickers.

• We add an event-driven variant to mscom::AsyncInvoker. When the async call
  invokes ISynchronize::Signal, we post an event to the specified event
  target (or implicitly to the main thread).
• For this to work, the async call needs to temporarily retain a reference to
  itself, otherwise the async call object is destroyed and the in-flight call
  is cancelled. This reference is stored in an "outer runnable" which is
  responsible for executing the inner completion runnable, and then dropping
  the self-reference.
• We only run the completion runnable upon successful initiation of the async
  call. If there was a failure, we return that code immediately to the caller.
  Failures also clear the reference to the completion runnable.
• If we could not obtain an async interface and must run synchronously, then
  we run the completion runnable immediately after a successful synchronous
  invocation.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/bb3aa2233400
Add a variant of mscom::AsyncInvoker that supports posting completion runnables; r=Jamie

Comment 3

[(No longer employed by Mozilla) Aaron Klotz]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=7801bee9bd084107d100b1c0502abdcf8bc23699

Comment 4

[Andreea Pavel [:apavel]]

https://hg.mozilla.org/mozilla-central/rev/bb3aa2233400