Resize events aren't delivered on OS X

[mitchmindtree]

Here's the relevant issue in glutin. I've only confirmed this on OS X 10.10.

The reason for this seems to be that cocoa (via glutin) requires that the user declares a resize_callback for resizing the window, rather than emitting an event as for all other events.

Events are blocked during resize on OS X within cocoa itself. Cocoa also requires that GL rendering occurs on the main thread (at least I'm pretty sure). I'm unsure whether or not events could be polled from a thread other than the main thread. Either way, any multi-threaded solutions are probably too heavy-weight for this lib or glutin.

For now, I guess we could have a special case for OS X where we create our own Resize events by comparing window sizes as @bvssvni suggests here, however this will only provide the event after the mouse is released and the event loop is unblocked, meaning that we still won't have live Resize or Render events during resizing.

I don't have any great solutions for this yet, just thought I'd post an issue to keep track.

[bvssvni]

piston_window checks the size of the frame buffer against the window: https://github.com/PistonDevelopers/piston_window/blob/master/src/lib.rs#L259, but doesn't emit resize events.

If glutin_window does this check instead, and it's consistent across the window backends, then piston_window could use resize events to change frame buffers.