Don't define the AVFoundation delegate more than once.

[leecbaker]

Fixes #25: This prevents a crash when multiple instances of the TTS engine are instantiated.

Here's what has changed: The delegate class (MyNSSpeechSynthesizerDelegate) should only be registered once; trying to register this a second time causes a crash. This class declaration is stored in a static variable, and reused.

The diff looks like much more code was much larger than it actually was, because the indentation level of the delegate class definition changed.

Code to demonstrate fix:

use tts::*;

#[cfg(target_os = "macos")]
use cocoa_foundation::base::id;
#[cfg(target_os = "macos")]
use cocoa_foundation::foundation::NSRunLoop;
#[cfg(target_os = "macos")]
use objc::{msg_send, sel, sel_impl};

fn main() {
    env_logger::init();

    let mut tts = Tts::default().unwrap();
    let mut tts2 = Tts::default().unwrap();

    tts.speak("Hello, world.", false).unwrap();
    tts2.speak("Hello, planet.", false).unwrap();
    tts.speak("Hello, again.", false).unwrap();

    #[cfg(target_os = "macos")]
    {
        let run_loop: id = unsafe { NSRunLoop::currentRunLoop() };
        unsafe {
            let _: () = msg_send![run_loop, run];
        }
    }
}

[ndarilek]

So sorry I haven't gotten to this. Long story short, my apartment is a disaster and I've been displaced for weeks.

Related: normally I perform due diligence and make sure the examples run on my mac, but since I'm not at home for the time being, I can't do that. If you can confirm that the examples still work, which I assume you have but I want to be sure, then I'll merge this and cut a new release.

Thanks for debugging this, and again, sorry for the delay.

[ndarilek]

ping If I don't have confirmation, I won't be able to merge this until I get back home in a week or two (hopefully.) Some mac users depend on this crate and I'm pretty sure they're not hitting this due to only initializing once. Need to be absolutely sure it works for them and I can't do that myself now.

Thanks.

[leecbaker]

Looks like I missed this comment earlier- sorry!

If you can confirm that the examples still work, which I assume you have but I want to be sure, then I'll merge this and cut a new release.

This did work on my mac, and does fix the issue with having multiple simultaneous instances; I've since run into another crash, this time with having multiple instances in sequence (i.e., initialize one instance, deinitialize it, then initialize a second without them existing simultaneously). I'm happy to wait to merge that until this problem is fixed as well.

In the long run, it might be best to have some types of tests run automatically, at least to verify that nothing crashes.

[ndarilek]

If you have thoughts on how to automate TTS testing in CI, do let me know. But it probably needs to be a manual process for now, especially given how it's fairly hard to measure a whole bunch of metrics like "Is the right voice actually speaking the right speed?" :) Let's go ahead and hold off until we get a full fix if you don't mind. This is a bit of a corner case for me for now, and I just want to make sure the fix for it is thorough. Thanks.