//! The adapter and the surface configuration the GPU measurement rigs share,
//! so the two cannot probe for a device in two different ways.

use wgpu::*;

/// An adapter on whatever this machine has, or `None` where there is none.
///
/// Probed rather than assumed: there may be no Vulkan adapter, and GL is what
/// is left when there is not.
///
/// The instance is leaked deliberately. A Vulkan loader may unload the driver
/// when the last one drops, which can fault as a thread that used it exits --
/// and every test runs on a spawned thread.
pub fn adapter() -> Option<Adapter> {
    let all = Instance::new(InstanceDescriptor::new_without_display_handle());
    let instance = match pollster::block_on(all.request_adapter(&RequestAdapterOptions::default()))
    {
        Ok(_) => all,
        Err(_) => Instance::new(InstanceDescriptor {
            backends: Backends::GL,
            ..InstanceDescriptor::new_without_display_handle()
        }),
    };
    let instance: &'static Instance = Box::leak(Box::new(instance));
    pollster::block_on(instance.request_adapter(&RequestAdapterOptions::default())).ok()
}

pub fn config(format: TextureFormat, size: u32) -> SurfaceConfiguration {
    SurfaceConfiguration {
        usage: TextureUsages::RENDER_ATTACHMENT,
        format,
        color_space: SurfaceColorSpace::Auto,
        width: size,
        height: size,
        present_mode: PresentMode::Fifo,
        desired_maximum_frame_latency: 2,
        alpha_mode: CompositeAlphaMode::Auto,
        view_formats: vec![],
    }
}