Type-information handle

[msiglreith]

Proposal

Expose following enum to only provide information about the window handle type, not the actual handle and a corresponding interface in the RawWindowHandle trait:

enum RawWindowHandleTy {
      AndroidHandle,
      X11Handle,
      WaylandHandle,
      WindowsHandle,
      ...
}

Motivation

On Android, it's not possible to gather the RawWindowHandle immediately after creation. At least for winit it can only be queried once certain events have been received in the event loop. This imposes restrictions for client apis, which relay on the information provided by the RawWindowHandle early on. I'm particular case it's related to deriving the required surface extensions for Vulkan WSI. Ideally, this could be soley derived from the introduced RawWindowHandleTy above as some platforms support multiple different WSI approaches.

Cons

• Breaking API changes
• Feels a bit like a bandaid but I'm currently lacking a better idea /:

Some more details and discussion over at winit: rust-windowing/winit#1624

[msiglreith]

Replaced by #54