wgpu draw triangle in rust

main.rs
use winit::{
    event::*,
    event_loop::{ControlFlow, EventLoop},
    window::{Window, WindowBuilder},
};

use wgpu::util::DeviceExt;

const VERTICES: &[f32] = &[
     0.0,  0.5, // top
    -0.5, -0.5, // bottom left
     0.5, -0.5, // bottom right
];

async fn run() {
    let instance = wgpu::Instance::new(wgpu::BackendBit::PRIMARY);
    let adapter = instance.request_adapter(
        &wgpu::RequestAdapterOptions {
            power_preference: wgpu::PowerPreference::Default,
            compatible_surface: None,
        },
    ).await.unwrap();
    let (mut device, mut queue) = adapter.request_device(
        &wgpu::DeviceDescriptor {
            features: wgpu::Features::empty(),
            limits: wgpu::Limits::default(),
            label: None,
        },
        None,
    ).await.unwrap();

    let mut event_loop = EventLoop::new();
    let window = WindowBuilder::new().build(&event_loop).unwrap();

    let surface = unsafe { instance.create_surface(&window) };
    let size = window.inner_size();
    let mut sc_desc = wgpu::SwapChainDescriptor {
        usage: wgpu::TextureUsage::OUTPUT_ATTACHMENT,
        format: surface.get_preferred_format(&adapter).unwrap(),
        width: size.width,
        height: size.height,
        present_mode: wgpu::PresentMode::Fifo,
    };
    let mut swap_chain = device.create_swap_chain(&surface, &sc_desc);

    let vs_module = device.create_shader_module(&wgpu::include_spirv!("shader.vert.spv"));
    let fs_module = device.create_shader_module(&wgpu::include_spirv!("shader.frag.spv"));
    
    let vertex_buffer = device.create_buffer_init(
        &wgpu::util::BufferInitDescriptor {
            label: Some("Vertex Buffer"),
            contents: bytemuck::cast_slice(VERTICES),
            usage: wgpu::BufferUsage::VERTEX,
        }
    );

    let pipeline_layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
        label: None,
        bind_group_layouts: &[],
        push_constant_ranges: &[],
    });

    let pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
        label: None,
        layout: Some(&pipeline_layout),
        vertex_stage: wgpu::ProgrammableStageDescriptor {
            module: &vs_module,
            entry_point: "main",
        },
        fragment_stage: Some(wgpu::ProgrammableStageDescriptor {
            module: &fs_module,
            entry_point: "main",
        }),
        rasterization_state: Some(wgpu::RasterizationStateDescriptor {
            front_face: wgpu::FrontFace::Ccw,
            cull_mode: wgpu::CullMode::Back,
            depth_bias: 0,
            depth_bias_slope_scale: 0.0,
            depth_bias_clamp: 0.0,
            clamp_depth: false,
        }),
        primitive_topology: wgpu::PrimitiveTopology::TriangleList,
        color_states: &[wgpu::ColorStateDescriptor {
            format: sc_desc.format,
            color_blend: wgpu::BlendDescriptor::REPLACE,
            alpha_blend: wgpu::BlendDescriptor::REPLACE,
            write_mask: wgpu::ColorWrite::ALL,
        }],
        depth_stencil_state: None,
        vertex_state: wgpu::VertexStateDescriptor {
            index_format: wgpu::IndexFormat::Uint16,
            vertex_buffers: &[wgpu::VertexBufferDescriptor {
                stride: 2 * std::mem::size_of::<f32>() as wgpu::BufferAddress,
                step_mode: wgpu::InputStepMode::Vertex,
                attributes: &[wgpu::VertexAttributeDescriptor {
                    offset: 0,
                    format: wgpu::VertexFormat::Float2,
                    shader_location: 0,
                }],
            }],
        },
        sample_count: 1,
        sample_mask: !0,
        alpha_to_coverage_enabled: false,
    });

    event_loop.run(move |event, _, control_flow| {
        *control_flow = ControlFlow::Poll;

        match event {
            Event::RedrawRequested(_) => {
                let output = swap_chain.get_current_frame().unwrap().output;
                let mut encoder = device.create_command_encoder(&wgpu::CommandEncoderDescriptor {
                    label: Some("Render Encoder"),
                });

                {
                    let mut render_pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                        label: None,
                        color_attachments: &[wgpu::RenderPassColorAttachmentDescriptor {
                            attachment: &output.view,
                            resolve_target: None,
                            ops: wgpu::Operations {
                                load: wgpu::LoadOp::Clear(wgpu::Color {
                                    r: 0.1,
                                    g: 0.2,
                                    b: 0.3,
                                    a: 1.0,
                                }),
                                store: true,
                            },
                        }],
                        depth_stencil_attachment: None,
                    });

                    render_pass.set_pipeline(&pipeline);
                    render_pass.set_vertex_buffer(0, vertex_buffer.slice(..));
                    render_pass.draw(0..3, 0..1);
                }

                queue.submit(Some(encoder.finish()));
            }
            Event::MainEventsCleared => {
                window.request_redraw();
            }
            Event::WindowEvent {
                event: WindowEvent::CloseRequested,
                ..
            } => *control_flow = ControlFlow::Exit,
            _ => {}
        }
    });
}

fn main() {
    env_logger::init();
    pollster::block_on(run());
}
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159 lines

#version 450

layout(location = 0) in vec2 a_pos;

void main() {
    gl_Position = vec4(a_pos, 0.0, 1.0);
}
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#version 450

layout(location = 0) out vec4 o_color;

void main() {
    o_color = vec4(1.0, 0.0, 0.0, 1.0);
}
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glsl-to-spirv shader.vert.glsl -o shader.vert.spv
glsl-to-spirv shader.frag.glsl -o shader.frag.spv
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