dunge 0.2.0

Simple and portable 3d render library
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use {
    crate::{postproc::PostProcessor, render::State},
    bytemuck::{Pod, Zeroable},
    std::sync::Arc,
    wgpu::{BindGroup, BindGroupLayout, Buffer, Queue},
};

pub(crate) struct PostShaderData {
    bind_group: BindGroup,
    buf: Buffer,
    queue: Arc<Queue>,
}

impl PostShaderData {
    pub fn new(state: &State, layout: &BindGroupLayout) -> Self {
        use wgpu::{
            util::{BufferInitDescriptor, DeviceExt},
            BindGroupDescriptor, BindGroupEntry, BufferUsages,
        };

        let device = state.device();
        let buf = {
            let uniform = PostShaderDataUniform::new((1., 1.), (1., 1.));
            device.create_buffer_init(&BufferInitDescriptor {
                label: Some("post data buffer"),
                contents: bytemuck::cast_slice(&[uniform]),
                usage: BufferUsages::UNIFORM | BufferUsages::COPY_DST,
            })
        };

        let bind_group = device.create_bind_group(&BindGroupDescriptor {
            layout,
            entries: &[BindGroupEntry {
                binding: PostProcessor::DATA_BINDING,
                resource: buf.as_entire_binding(),
            }],
            label: Some("post bind group"),
        });

        Self {
            bind_group,
            buf,
            queue: Arc::clone(state.queue()),
        }
    }

    pub fn resize(&self, size: (f32, f32), factor: (f32, f32)) {
        let uniform = PostShaderDataUniform::new(size, factor);
        self.queue
            .write_buffer(&self.buf, 0, bytemuck::cast_slice(&[uniform]));
    }

    pub fn bind_group(&self) -> &BindGroup {
        &self.bind_group
    }
}

#[repr(C)]
#[derive(Copy, Clone, Pod, Zeroable)]
struct PostShaderDataUniform {
    size: [f32; 2],
    step: [f32; 2],
    factor: [f32; 2],
    pad: u64,
}

impl PostShaderDataUniform {
    fn new(size: (f32, f32), factor: (f32, f32)) -> Self {
        const STEP_FACTOR: f32 = 0.5;

        let size = size.into();
        Self {
            size,
            step: size.map(|v| STEP_FACTOR / v),
            factor: factor.into(),
            pad: 0,
        }
    }
}