poll_events()/wait_events() are not enough for power efficient GUI apps

[pedrocr]

The current events API is not enough to be able to have a GUI app that can both sit idle for minutes/hours when there are no new events as well as reacts to outside events not from the GUI. With the two current APIs you can:

• poll_events(): Run a 60fps loop by first polling for events, then checking for outside events, then sleeping for 16ms. This gives you the correct behavior but has 60 wakeups per second which costs a bit of power.
• wait_events(): Since it blocks the power issue is solved but there is then no way to react to other events.

The ideal API would be a form of wait_events() with a way to inject an artificial event from another thread so that it can be unblocked on demand. Maybe there's already a way of doing this?

[pedrocr]

Btw I came across this limitation while working on a conrod app event loop:

PistonDevelopers/conrod#915

[jwilm]

@pedrocr You can get a WindowProxy which has a wakeup_event_loop() method. Looks like event iterators are going go away soon anyway.

[pedrocr]

@jwilm thanks, this does indeed work fine and makes for very simple code.