Feature request: Custom URI handling

[FredrikNoren]

Hi!

I'm not sure if it's in scope of winit or not, but it would be fantastic if it handled custom uri's; like this: https://developer.apple.com/documentation/xcode/defining-a-custom-url-scheme-for-your-app

https://github.com/maidsafe-archive/system_uri does provide the registration functionality, and it works if the app isn't already running (the app opens with an argument with the uri). But if the app is already running I think something more needs to be done to handle it (at least on OSX). I haven't looked into it in detail, but it feels like it would fit pretty well as a WindowEvent.

[madsmtm]

Related: #1759.

Not sure if this is supported on other platforms?

[maroider]

Of the desktop platforms, macOS seems to be the only one requiring hooking into winit in some manner. On Windows and Linux, the application is just started a second time if the application is already running, and I suspect Android and iOS will have similar issues as macOS.

[nicoburns]

Iced has been maintaining a fork of winit primarily for this feature (implementation here: https://github.com/iced-rs/winit/pull/1/files). Would winit be open to accepting this upstream?

[Xaeroxe]

I'd love to get iced back on the upstream winit personally. I'm happy to provide labor to make it happen, I just need someone to point me in a direction.

[wyatt-herkamp]

What is holding this feature back?

[madsmtm]

#3825 has been opened to resolve this, though I'm currently fairly sure that it is unnecessary, and that this feature is implement-able outside of Winit after #3758, see #3825 (review).

[madsmtm]

See ^, I'm confident that this is implementable outside Winit once v0.31 is released. If someone writes a helper crate to do this, I'd love to link to that in docs.

Btw, not sure I gave my full reasoning for why I prefer it like this (maybe a bit in #1751 (comment)), but it's basically:

1. There are a lot of NSApplicationDelegate callbacks, and I already maintain one set of bindings for it - I don't want to maintain two ;).
2. Any wrapper we do that is cleaner / more Rusty than objc2-app-kit will inevitably also either be less flexible or less efficient.
3. Users might prefer to write their delegate in plain Objective-C, so we need some sort of opt-out anyhow. And then we'd have to document that Winit's methods won't be called in such cases. Yuck!