Revamped API Proposal

In the interest of simplifying the surfman and preparing for adding support for interoperability with wgpu and for cross-process surface handles, I would like to propose version 2 of the API:

Connection

pub enum Connection {
    Android(...),
    Angle(...),
    Cgl(...),
    Ohos(...),
    SurfacelessMesa(...),
    Wayland(...),
    Wgl(...),
    X11(...),
}

Adapter

pub enum Adapter {
    Android(...),
    Angle(...),
    Cgl(...),
    Egl(...),
    Ohos(...),
    Wgl(...),
}

Surface

pub enum Surface {
    Window(WindowSurface),
    Buffer(BufferSurface),
}

pub enum BufferSurface {
    Android(...),
    Direct3d(...),
    IoSurface(...)
    Ohos(...),
    Pbuffer(...),
}

pub enum WindowSurface {
    Android(...),
    AppKit(...)
    Ohos(...),
    Wayland(...),
    Win32(...),
    X11(...),
}

Notes:

• Only WindowSurface would implement present meaning it's not possible to call present on a buffer surface (this causes an error today).
• Mutability concerns would be handled by a mutable getter for the currently bound surface:

  if let Some(Surface::Window(window_surface)) = cnnection.bound_surface_mut() {
      window_surface.present(&device);
  }
  

• Multi is eliminated. Instead a factory returns the most appropriate context given what is enabled at compile-time and what is currently running (when choosing between X11 and Wayland).
• This opens up the possibility of other kinds of offscreen buffers such as GBM, which will be necessary for cross-process rendering and integration with wgpu.
• The idea is that BufferSurface will provide a fallible method to get a shareable handle to be used for cross-process surfaces.

This is an API design proposal: no files, tests, or implementation entry points are named. Review the proposed Connection, Adapter, Surface, BufferSurface, and WindowSurface shapes first, then establish compatibility and acceptance criteria for wgpu and cross-process handles; the issue does not define what completion looks like.