raw-window-handle: the handshake

use book_error::Result;
use raw_window_handle::{HasWindowHandle, RawWindowHandle};

/// What kind of native object is behind this window?
/// Asking can fail, for example if the window has not been created yet.
fn describe(window: &impl HasWindowHandle) -> Result<&'static str> {
    let handle = window.window_handle()?;
    Ok(match handle.as_raw() {
        RawWindowHandle::AppKit(_) => "NSView (macOS)",
        RawWindowHandle::Win32(_) => "HWND (Windows)",
        RawWindowHandle::Xlib(_) | RawWindowHandle::Xcb(_) => "X11 window",
        RawWindowHandle::Wayland(_) => "wl_surface (Wayland)",
        RawWindowHandle::Web(_) => "canvas element (browser)",
        _ => "something else",
    })
}

fn main() {
    // winit's Window implements HasWindowHandle, so this just works:
    let _ = |w: &winit::window::Window| describe(w);
}

use book_error::Result;
use raw_window_handle::{HasDisplayHandle, HasWindowHandle};

/// This bound is the entire contract between a window library and a renderer.
/// wgpu, glutin, softbuffer and Slint's backends all ask for exactly this.
trait RenderTarget: HasWindowHandle + HasDisplayHandle {}
impl<T: HasWindowHandle + HasDisplayHandle> RenderTarget for T {}

fn create_surface(target: &dyn RenderTarget) -> Result<()> {
    // Either handle can be unavailable, so both are fallible.
    let _window = target.window_handle()?;
    let _display = target.display_handle()?;
    // ...hand the raw handles to Metal / Vulkan / D3D / WebGPU here...
    Ok(())
}

fn main() {
    // winit's Window satisfies it, so does tao's, and so does any test double.
    let _: fn(&winit::window::Window) -> Result<()> = |w| create_surface(w);
}